VOUT
RON/SD
FB
VIN
SW
RTN
BST
L1
C2
R1
R2
C4
C3
C1
SHUTDOWN RCL
VCC
D1
RON
RCL
9.5 - 95V
Input
LM5009
LM5009
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SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
150-mA 100-V Step-Down Switching Regulator
Check for Samples: LM5009
1FEATURES DESCRIPTION
The LM5009 Step Down Switching Regulator features
2• Integrated N-Channel MOSFET all of the functions needed to implement a low cost,
• 150-mA output current capability efficient, Buck bias regulator. This device is capable
• Ultra-Fast Transient Response of driving a 150 mA load current from a 9.5V to 95V
input source. The switching frequency can exceed
• No loop compensation required 600 kHz, depending on the input and output voltages.
• Vin feed forward provides constant operating The output voltage may be set from 2.5V to 85V. This
frequency high voltage regulator contains an N-Channel buck
• Switching frequency can exceed 600 kHz switch and internal startup regulator. The device is
easy to implement and is provided in the 8-pin
• Highly efficient operation VSSOP and the thermally enhanced 8-pin WSON
• 2% accurate 2.5V feedback from -40°C to packages. The LM5009 is a well suited alternative to
125°C a high voltage monolithic or discrete linear solution
• Internal startup regulator where the power loss becomes unacceptable. The
regulator’s operation is based on a control scheme
• Intelligent current limit protection using an ON time inversely proportional to VIN. This
• External shutdown control feature allows the operating frequency to remain
• Thermal shutdown relatively constant over load and input voltage
variations. The control scheme requires no loop
• 8-Pin VSSOP and thermally enhanced 8-Pin compensation, resulting in an ultra-fast transient
WSON packages response. An intelligent current limit is implemented
with forced OFF time, which is inversely proportional
APPLICATIONS to Vout. This scheme ensures short circuit protection
• Heat sink eliminator for classic linear regulator while providing minimum foldback. Other features
applications include: Thermal Shutdown, Vcc under-voltage
lockout, Gate drive under-voltage lockout, and
• 12V, 24V, 36V, and 48V rectified AC systems Maximum Duty Cycle limiter.
• 42V Automotive
• Non-isolated AC mains charge coupled
supplies
• LED Current Source
Typical Application Circuit
Figure 1. Basic Step-Down Regulator
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2006–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
1
2
3
4 5
6
7
8
SW
BST
RCL
FB
RTN
RON/SD
VCC
VIN
LM5009
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
www.ti.com
Connection Diagram
Figure 2. 8-Lead VSSOP or WSON
Pin Functions
Table 1. Pin Descriptions
Pin Name Description Application Information
1 SW Switching output Power switching output. Connect to the inductor, re-circulating diode, and bootstrap
capacitor.
2 BST Boost Pin An external capacitor is required between the BST and the SW pins. A 0.022 µF
ceramic capacitor is recommended. An internal diode charges the capacitor from
VCC.
3 RCL Current Limit off-time set A resistor between this pin and RTN sets the off-time when current limit is detected.
pin The off-time is preset to 35µs if FB = 0V.
4 RTN Ground pin Ground for the entire circuit.
5 FB Feedback input from This pin is connected to the inverting input of the internal regulation comparator. The
Regulated Output regulation threshold is 2.5V.
6 RON/SD On-time set pin A resistor between this pin and VIN sets the switch on-time as a function of VIN. The
minimum recommended on-time is 250ns at the maximum input voltage. This pin
can be used for remote shutdown.
7 VCC Output from the internal If an auxiliary voltage is available to raise the voltage on this pin above the
high voltage startup regulation set point (7V), the internal series pass regulator will shutdown, reducing
regulator. Regulated at the IC power dissipation. Do not exceed 14V. This voltage provides gate drive
7.0V. power for the internal Buck switch. An internal diode is provided between this pin
and the BST pin. A local 0.1µF decoupling capacitor is required.
8 VIN Input voltage Recommended operating range: 9.5V to 95V.
EP Exposed pad Exposed metal pad on the underside of the device. It is recommended to connect
(WSON package only) this to the PC board ground plane to aid in heat dissipation.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings(1)
VIN to RTN -0.3V to 100V
BST to RTN -0.3V to 114V
SW to RTN (Steady State) -1V
ESD Rating, Human Body Model(2) 2kV
BST to VCC 100V
BST to SW 14V
VCC to RTN 14V
All Other Inputs to RTN -0.3 to 7V
Storage Temperature Range -65°C to +150°C
(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which
operation of the device is intended to be functional. For specifications and test conditions, see the Electrical Characteristics.
(2) The human body model is a 100pF capacitor discharged through a 1.5kΩresistor into each pin.
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LM5009
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Operating Ratings(1)
VIN 9.5V to 95V
Operating Junction Temperature −40°C to + 125°C
(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which
operation of the device is intended to be functional. For specifications and test conditions, see the Electrical Characteristics.
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Electrical Characteristics
Limits in standard type are for TJ= 25°C only, and limits in boldface type apply over the junction temperature (TJ) range of
‑40°C to +125°C. Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values
represent the most likely parametric norm at TJ= 25°C, and are provided for reference purposes only. Unless otherwise
stated, the following conditions apply: VIN = 48V, RON = 200kΩ. See (1)
Symbol Parameter Conditions Min Typ Max Unit
VCC Supply
VCC Reg VCC Regulator Output 6.6 77.4 V
VCC Current Limit(2) 9.5 mA
VCC undervoltage Lockout 6.3 V
Voltage (VCC increasing)
VCC Undervoltage Hysteresis 200 mV
VCC UVLO Delay (filter) 100mV overdrive 10 µs
IIN Operating Current Non-Switching, FB = 3V 485 675 µA
IIN Shutdown Current RON/SD = 0V 76 150 µA
Switch Characteristics
Buck Switch Rds(on) ITEST = 200mA(3) 2.0 4.4 Ω
Gate Drive UVLO VBST −VSW Rising 3.4 4.5 5.5 V
Gate Drive UVLO Hysteresis 430 mV
Current Limit
Current Limit Threshold 0.25 0.31 0.37 A
Current Limit Response Time Iswitch Overdrive = 0.1A Time to Switch Off 400 ns
OFF time generator (test 1) FB=0V, RCL = 100K 35 µs
OFF time generator (test 2) FB=2.3V, RCL = 100K 2.56 µs
On Time Generator
TON - 1 Vin = 10V, Ron = 200K 2.15 2.77 3.5 µs
TON - 2 Vin = 95V, Ron = 200K 200 300 420 ns
Remote Shutdown Threshold Rising 0.40 0.70 1.05 V
Remote Shutdown Hysteresis 35 mV
Minimum Off Time
Minimum Off Timer FB = 0V 300 ns
Regulation and OV Comparators
FB Reference Threshold Internal reference, Trip point for switch ON 2.445 2.5 2.550 V
FB Over-Voltage Threshold Trip point for switch OFF 2.875 V
FB Bias Current 1 nA
Thermal Shutdown
Tsd Thermal Shutdown Temperature 165 °C
Thermal Shutdown Hysteresis 25 °C
Thermal Resistance
θJA Junction to Ambient VSSOP Package 200 °C/W
WSON Package 40 °C/W
(1) All electrical characteristics having room temperature limits are tested during production with TA= TJ= 25°C. All hot and cold limits are
specified by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
(2) The VCC output is intended as a self bias for the internal gate drive power and control circuits. Device thermal limitations limit external
loading.
(3) For devices procured in the WSON-8 package, the Rds(on) limits are specified by design characterization data only.
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89 10 11 12 13 14
EXTERNALLY APPLIED VCC (V)
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
ICC INPUT CURRENT (mA)
FS = 1.2 MHz
FS = 725 kHz
FS = 180 kHz
FS = 400 kHz
0 2 4 6 8 10
0
1
2
3
4
5
6
7
8
VCC (V)
ICC (mA, External Load)
VIN = 9.5V
10V
VIN t 15V
0 0.5 1.0 1.5 2.0 2.5
0
5
10
15
20
25
30
35
CURRENT LIMIT OFF TIME (Ps)
VFB (V)
300k
RCL = 500k
100k
50k
VIN (V)
020 40 60 80 100
ON-TIME (Ps)
0.1
1.0
10
Ron = 500k
300k
100k
1.2 MHz
725 kHz
400 kHz
VIN (V)
6.5
VCC (V)
9.0 9.5 10.0 10.5 11.0
6.6
6.7
6.8
6.9
7.0
7.1 FS = 180 kHz
LM5009
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SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
Typical Performance Characteristics
On-Time vs \ VIN and RON VCC vs VIN and FS
Figure 3. Figure 4.
Current Limit Off-Time vs VCC vs
VFB and RCL ICC and VIN
Figure 5. Figure 6.
ICC Current vs
Applied VCC Voltage
Figure 7.
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Product Folder Links: LM5009
FB
VIN
VCC
SW
RTN
ON TIMER
DRIVER
VIN
BST
LEVEL
SHIFT
SD/
RON
2.5V
THERMAL
SHUTDOWN
0.31A
BUCK
SWITCH
CURRENT
SENSE
COMPLETE
RCL START
RCL
COMPLETE
START
Ron
L1
C4
9.5V - 95V
Input
C3
LM5009
UVLO
FB
UVLO
REGULATION
COMPARATOR
OVER-VOLTAGE
COMPARATOR
2.875V
SD
SD
COMPLETE
START
MINIMUM
OFF-TIMER
8
6
5
3
4
1
2
7
7V SERIES
REGULATOR
CURRENT LIMIT
OFF TIMER
SHUTDOWN
D1
Q
CLR
Q
SET
S
R
+
-
+
-
+
-
C1
RON
RCL
R2
R3
VOUT2
VOUT1
R1
C5
C2
LM5009
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
www.ti.com
TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM
Figure 8.
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F = VOUT
1.25 x 10-10 x RON
LM5009
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SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
FUNCTIONAL DESCRIPTION
The LM5009 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient,
Buck bias power converter. This high voltage regulator contains a 100 V N-Channel Buck Switch, is easy to
implement and is provided in the VSSOP-8 and the thermally enhanced WSON-8 packages. The regulator is
based on a control scheme using an on-time inversely proportional to VIN. The control scheme requires no loop
compensation. Current limit is implemented with forced off-time, which is inversely proportional to VOUT. This
scheme ensures short circuit protection while providing minimum foldback. The Functional Block Diagram of the
LM5009 is shown in Figure 8.
The LM5009 can be applied in numerous applications to efficiently regulate down higher voltages. This regulator
is well suited for 48 Volt Telecom and the 42V Automotive power bus ranges. Additional features include:
Thermal Shutdown, VCC under-voltage lockout, Gate drive under-voltage lockout, Max Duty Cycle limit timer and
the intelligent current limit off timer.
Control Circuit Overview
The LM5009 is a Buck DC-DC regulator that uses a control scheme in which the on-time varies inversely with
line voltage (VIN). Control is based on a comparator and the on-time one-shot, with the output voltage feedback
(FB) compared to an internal reference (2.5V). If the FB level is below the reference the buck switch is turned on
for a fixed time determined by the line voltage and a programming resistor (RON). Following the ON period the
switch will remain off for at least the minimum off-timer period of 300 ns. If FB is still below the reference at that
time the switch will turn on again for another on-time period. This will continue until regulation is achieved, at
which time the off-time increases based on the required duty cycle.
The LM5009 operates in discontinuous conduction mode at light load currents, and continuous conduction mode
at heavy load current. In discontinuous conduction mode, current through the output inductor starts at zero and
ramps up to a peak during the on-time, then ramps back to zero before the end of the off-time. The next on-time
period starts when the voltage at FB falls below the internal reference - until then the inductor current remains
zero. In this mode the operating frequency is lower than in continuous conduction mode, and varies with load
current. Therefore at light loads the conversion efficiency is maintained, since the switching losses reduce with
the reduction in load and frequency. The discontinuous operating frequency can be calculated as follows:
(1)
where RL= the load resistance
In continuous conduction mode, current flows continuously through the inductor and never ramps down to zero.
In this mode the operating frequency is greater than the discontinuous mode frequency and remains relatively
constant with load and line variations. The approximate continuous mode operating frequency can be calculated
as follows:
(2)
The output voltage (VOUT) is programmed by two external resistors as shown in Figure 8. The regulation point is
calculated as follows:
VOUT = 2.5 x (R1 + R2) / R2 (3)
This regulator regulates the output voltage based on ripple voltage at the feedback input, requiring a minimum
amount of ESR for the output capacitor C2. A minimum of 25mV of ripple voltage at the feedback pin (FB) is
required for the LM5009. In cases where the capacitor ESR is too small, additional series resistance may be
required (R3 in Figure 8).
For applications where lower output voltage ripple is required the output can be taken directly from a low ESR
output capacitor, as shown in Figure 9. However, R3 slightly degrades the load regulation.
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FB
SW
L1
C2
VOUT1
R3
LM5009
BST
VCC
C4
D2
D1 R1
R2
C3
FB
SW
L1
C2
R1
R2
VOUT2
R3
LM5009
LM5009
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
www.ti.com
Figure 9. Low Ripple Output Configuration
High Voltage Start-Up Regulator
The LM5009 contains an internal high voltage startup regulator. The input pin (VIN) can be connected directly to
line voltages up to 95 Volts, with transient capability to 100 volts. The regulator is internally current limited at
9.5mA. Upon power up, the regulator sources current into the external capacitor at VCC (C3). When the voltage
on the VCC pin reaches the under-voltage lockout threshold of 6.3V, the buck switch is enabled.
In applications involving a high value for VIN, where power dissipation in the VCC regulator is a concern, an
auxiliary voltage can be diode connected to the VCC pin. Setting the voltage between 8V and 14V shuts off the
internal regulator, reducing internal power dissipation. See Figure 10. The current required into the VCC pin is
shown in the Typical Performance Characteristics.
Figure 10. Self-Biased Configuration
Regulation Comparator
The feedback voltage at FB is compared to an internal 2.5V reference. In normal operation (the output voltage is
regulated), an on-time period is initiated when the voltage at FB falls below 2.5V. The buck switch will stay on for
the programmed on-time, causing the FB voltage to rise above 2.5V. After the on-time period, the buck switch
will stay off until the FB voltage again falls below 2.5V. During start-up, the FB voltage will be below 2.5V at the
end of each on-time, resulting in the minimum off-time. Bias current at the FB pin is less than 5 nA over
temperature.
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TOFF = VFB
(6.35 x 10-6 x RCL)
0.285 +
10-5
STOP
RUN
RON LM5009
RON/SD
VIN
Input
Voltage
LM5009
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SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
Over-Voltage Comparator
The feedback voltage at FB is compared to an internal 2.875V reference. If the voltage at FB rises above 2.875V
the on-time pulse is immediately terminated. This condition can occur if the input voltage, or the output load,
change suddenly. The buck switch will not turn on again until the voltage at FB falls below 2.5V.
ON-Time Generator and Shutdown
The on-time for the LM5009 is determined by the RON resistor, and is inversely proportional to the input voltage
(Vin), resulting in a nearly constant frequency as Vin is varied over its range. The on-time equation is:
TON = 1.25 x 10-10 x RON / VIN (4)
RON should be selected for a minimum on-time (at maximum VIN) greater than 250 ns, for proper current limit
operation. This requirement limits the maximum frequency for each application, depending on VIN and VOUT.
The LM5009 can be remotely disabled by taking the RON/SD pin to ground. See Figure 11. The voltage at the
RON/SD pin is between 1.7V and 5V, depending on Vin and the value of the RON resistor.
Figure 11. Shutdown Implementation
Current Limit
The LM5009 contains an intelligent current limit OFF timer. If the current in the Buck switch exceeds 0.31A the
present cycle is immediately terminated, and a non-resetable OFF timer is initiated. The length of off-time is
controlled by an external resistor (RCL) and the FB voltage. When FB = 0V, a maximum off-time is required, and
the time is preset to 35µs. This condition occurs when the output is shorted, and during the initial part of start-up.
This amount of time ensures safe short circuit operation up to the maximum input voltage of 95V. In cases of
overload where the FB voltage is above zero volts (not a short circuit) the current limit off-time will be less than
35µs. Reducing the off-time during less severe overloads reduces the amount of foldback, recovery time, and the
start-up time. The off-time is calculated from the following equation:
(5)
The current limit sensing circuit is blanked for the first 50-70ns of each on-time so it is not falsely tripped by the
current surge which occurs at turn-on. The current surge is required by the re-circulating diode (D1) for its turn-
off recovery.
N-Channel Buck Switch and Driver
The LM5009 integrates an N-Channel buck switch and associated floating high voltage gate driver. The gate
driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A
0.022‑µF ceramic capacitor (C4) connected between the BST pin and SW pin provides the voltage to the driver
during the on-time.
During each off-time, the SW pin is at approximately -1V, and the bootstrap capacitor charges from Vcc through
the internal diode. The minimum OFF timer ensures a minimum time each cycle to recharge the bootstrap
capacitor.
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An external re-circulating diode (D1) carries the inductor current after the internal buck switch turns off. This
diode should be of the ultra-fast or Schottky type to minimize turn-on losses and current over-shoot.
Thermal Protection
The LM5009 should be operated so the junction temperature does not exceed 125°C during normal operation.
An internal Thermal Shutdown circuit is provided to protect the LM5009 in the event of a higher than normal
junction temperature. When activated, typically at 165°C, the controller is forced into a low power reset state,
disabling the buck switch. This feature prevents catastrophic failures from accidental device overheating. When
the junction temperature reduces below 140°C (typical hysteresis = 25°C), the buck switch is enabled, and
normal operation is resumed.
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L1 = VOUT1 x (VIN - VOUT1)
IOR x Fs x VIN
LM5009
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SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
APPLICATIONS INFORMATION
SELECTION OF EXTERNAL COMPONENTS
A guide for determining the component values will be illustrated with a design example. Refer to Figure 8. The
following steps will configure the LM5009 for:
• Input voltage range (Vin): 12V to 90V
• Output voltage (VOUT1): 10V
• Load current (for continuous conduction mode): 100mA to 150mA
R1 and R2: From Figure 8, VOUT1 = VFB x (R1 + R2) / R2, and since VFB = 2.5V, the ratio of R1 to R2 calculates
as 3:1. Standard values of 3.01 kΩ(R1) and 1.00 kΩ(R2) are chosen. Other values could be used as long as
the 3:1 ratio is maintained. The selected values, however, provide a small amount of output loading (2.5 mA) in
the event the main load is disconnected. This allows the circuit to maintain regulation until the main load is
reconnected.
Fsand RON:Unless the application requires a specific frequency, the choice of frequency is generally a
compromise since it affects the size of L1 and C2, and the switching losses. The maximum allowed frequency,
based on a minimum on-time of 250 ns, is calculated from:
FMAX = VOUT / (VINMAX x 250 ns) (6)
For this exercise, Fmax = 444 kHz. From Equation 2, RON calculates to 180 kΩ. A standard value 237 kΩresistor
will be used to allow for tolerances in Equation 2, resulting in a nominal frequency of 337 kHz.
L1: The main parameter affected by the inductor is the output current ripple amplitude. The choice of inductor
value therefore depends on both the minimum and maximum load currents, keeping in mind that the maximum
ripple current occurs at maximum Vin.
a) Minimum load current: To maintain continuous conduction at minimum Io (100 mA), the ripple amplitude
(IOR) must be less than 200 mA peak-to-peak so the lower peak of the waveform does not reach zero. L1 is
calculated using the following equation:
(7)
At Vin = 90V, L1(min) calculates to 132 µH. The next larger standard value (150 µH) is chosen and with this
value IOR calculates to 176 mA peak-to-peak at Vin = 90V, and 33 mA peak-to-peak at Vin = 12V.
b) Maximum load current: At a load current of 150 mA, the peak of the ripple waveform must not reach the
minimum value of the LM5009’s current limit threshold (250 mA). Therefore the ripple amplitude must be less
than 200 mA peak-to-peak, which is already satisfied in the above calculation. With L1 = 150 µH, at maximum
Vin and Io, the peak of the ripple will be 238 mA. While L1 must carry this peak current without saturating or
exceeding its temperature rating, it also must be capable of carrying the maximum value of the LM5009’s current
limit threshold (370 mA) without saturating, since the current limit is reached during startup.
C3: The capacitor on the VCC output provides not only noise filtering and stability, but also prevents false
triggering of the VCC UVLO at the buck switch on/off transitions. For this reason, C3 should be no smaller than
0.1 µF.
C2, and R3: When selecting the output filter capacitor C2, the items to consider are ripple voltage due to its
ESR, ripple voltage due to its capacitance, and the nature of the load.
a) ESR and R3: A low ESR for C2 is generally desirable so as to minimize power losses and heating within the
capacitor. However, this regulator requires a minimum amount of ripple voltage at the feedback input for proper
loop operation. For the LM5009 the minimum ripple required at pin 5 is 25 mV peak-to-peak, requiring a
minimum ripple at VOUT1 of 100 mV. Since the minimum ripple current (at minimum Vin) is 33 mA peak-to-peak,
the minimum ESR required at VOUT1 is 3 Ω. Since quality capacitors for SMPS applications have an ESR
considerably less than this, R3 is inserted as shown in Figure 8. R3’s value, along with C2’s ESR, must result in
at least 25 mV peak-to-peak ripple at pin 5. Generally, R3 will be 0.5 Ωto 5.0 Ω.
b) Nature of the Load: The load can be connected to VOUT1 or VOUT2. VOUT1 provides good regulation, but with a
ripple voltage which ranges from 100 mV (at Vin = 12V) to 580 mV (at Vin = 90V). Alternatively, VOUT2 provides
low ripple (3 mV to 13 mV) but lower regulation due to R3.
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C1 = I x tON
'V0.15A x 2.47 Ps
2.0V
== 0.185 PF
LM5009
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C2 should generally be no smaller than 3.3 µF. Typically, its value is 10 µF to 20 µF, with the optimum value
determined by the load. If the load current is fairly constant, a small value suffices for C2. If the load current
includes significant transients, a larger value is necessary. For each application, experimentation is needed to
determine the optimum values for R3 and C2.
C) Ripple Reduction: The ripple amplitude at VOUT1 can be reduced by reducing R3, and adding a capacitor
across R1 so as to transfer the ripple at VOUT1 directly to the FB pin, without attenuation. The new value of R3 is
calculated from:
R3 = 25 mV/IOR(min) (8)
where IOR(min) is the minimum ripple current amplitude - 33 mAp-p in this example. The added capacitor's value is
calculated from:
C = TON(max)/(R1 // R2) (9)
where TON(max) is the maximum on-time (at minimum Vin). The selected capacitor should be larger than the value
calculated above.
RCL:When a current limit condition is detected, the minimum off-time set by this resistor must be greater than the
maximum normal off-time which occurs at maximum Vin. Using Equation 4, the minimum on-time is 0.329 µs,
yielding a maximum off-time of 2.63 µs. This is increased by 82 ns (to 2.72 µs) due to a ±25% tolerance of the
on-time. This value is then increased to allow for:
The response time of the current limit detection loop (400ns).
The off-time determined by Equation 5 has a ±25% tolerance:
tOFFCL(MIN) = (2.72 µs x 1.25) + 0.4 µs= 3.8 µs (10)
Using Equation 5, RCL calculates to 167 kΩ(at VFB = 2.5V). The closest standard value is 169 kΩ.
D1: The important parameters are reverse recovery time and forward voltage. The reverse recovery time
determines how long the reverse current surge lasts each time the buck switch is turned on. The forward voltage
drop is significant in the event the output is short-circuited as it is only this diode’s voltage which forces the
inductor current to reduce during the forced off-time. For this reason, a higher voltage is better, although that
affects efficiency. A good choice is an ultrafast power or Schottky diode with a reverse recovery time of ≊30 ns,
and a forward voltage drop of ≊0.7V. Other types of diodes may have a lower forward voltage drop, but may
have longer recovery times, or greater reverse leakage. D1’s reverse voltage rating must be at least as great as
the maximum Vin, and its current rating be greater than the maximum current limit threshold (370 mA).
C1: This capacitor’s purpose is to supply most of the switch current during the on-time, and limit the voltage
ripple at VIN, on the assumption that the voltage source feeding VIN has an output impedance greater than zero.
At maximum load current, when the buck switch turns on, the current into pin 8 will suddenly increase to the
lower peak of the output current waveform, ramp up to the peak value, then drop to zero at turn-off. The average
input current during this on-time is the load current (150 mA). For a worst case calculation, C1 must supply this
average load current during the maximum on-time. To keep the input voltage ripple to less than 2V (for this
exercise), C1 calculates to:
(11)
Quality ceramic capacitors in this value have a low ESR which adds only a few millivolts to the ripple. It is the
capacitance which is dominant in this case. To allow for the capacitor’s tolerance, temperature effects, and
voltage effects, a 1.0 µF, 100V, X7R capacitor will be used.
C4: The recommended value is 0.022 µF for C4, as this is appropriate in the majority of applications. A high
quality ceramic capacitor, with low ESR is recommended as C4 supplies the surge current to charge the buck
switch gate at turn-on. A low ESR also ensures a quick recharge during each off-time. At minimum VIN, when
the on-time is at maximum, it is possible during start-up that C4 will not fully recharge during each 300 ns off-
time. The circuit will not be able to complete the start-up, and achieve output regulation. This can occur when the
frequency is intended to be low (e.g., RON = 500K). In this case C4 should be increased so it can maintain
sufficient voltage across the buck switch driver during each on-time.
C5: This capacitor helps avoid supply voltage transients and ringing due to long lead inductance at VIN. A low
ESR, 0.1µF ceramic chip capacitor is recommended, located close to the LM5009.
12 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM5009
FB
VIN
SW
RTN
BST
LM5009
8
6
5
3
4
1
2
7
SHUTDOWN
VCC
RCL
RON/SD
12V - 90V
Input
237k
C1
1.0 PF
RON
RCL
169k R2
1.0k
R1
3.01k R3
3.0
GND
C2
15 PF
VOUT2
VOUT1
10.0V
L1
150 PH
C3
0.1 PF
C4
0.022 PF
D1
C5
0.1 PF
LM5009
www.ti.com
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
FINAL CIRCUIT
The final circuit is shown in Figure 12. The circuit was tested, and the resulting performance is shown in
Figure 13 through Figure 16. For these graphs, the load current was varied from 50mA to 200mA.
MINIMUM LOAD CURRENT
A minimum load current of 1 mA is required to maintain proper operation. If the load current falls below that level,
the bootstrap capacitor may discharge during the long off-time, and the circuit will either shutdown, or cycle on
and off at a low frequency. If the load current is expected to drop below 1 mA in the application, the feedback
resistors should be chosen low enough in value so they provide the minimum required current at nominal Vout.
PC BOARD LAYOUT
The LM5009 regulation and over-voltage comparators are very fast, and as such will respond to short duration
noise pulses. Layout considerations are therefore critical for optimum performance. The components at pins 1, 2,
3, 5, and 6 should be as physically close as possible to the IC, thereby minimizing noise pickup in the PC tracks.
The current loop formed by D1, L1, and C2 should be as small as possible. The ground connection from C2 to
C1 should be as short and direct as possible.
If the internal dissipation of the LM5009 produces excessive junction temperatures during normal operation, good
use of the PC board’s ground plane can help considerably to dissipate heat. The exposed pad on the bottom of
the WSON-8 package can be soldered to a ground plane on the PC board, and that plane should extend out
from beneath the IC to help dissipate the heat. Additionally, the use of wide PC board traces, where possible,
can also help conduct heat away from the IC. Judicious positioning of the PC board within the end product, along
with use of any available air flow (forced or natural convection) can help reduce the junction temperatures.
Figure 12. LM5009 Example Circuit
Copyright © 2006–2013, Texas Instruments Incorporated Submit Documentation Feedback 13
Product Folder Links: LM5009
0 20 40 60 80 100
230
250
270
290
310
330
LOAD CURRENT @ CURRENT LIMIT
ONSET (mA)
VIN (V)
LOAD CURRENT (mA)
VOUT (V)
50 100 150 200
9.4
9.6
9.8
10.0
10.2
10.4
Vin = 48V
0 20 40 60 80 100
50
60
70
80
90
100
EFFICIENCY (%)
VIN (V)
IOUT = 200 mA
IOUT = 100 mA
LOAD CURRENT (mA)
EFFICIENCY (%)
Vin = 12V
50 100 150 200
50
60
70
80
90
100
Vin = 90V
Vin = 48V
Vin = 30V
LM5009
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
www.ti.com
Table 2. Bill of Materials (Circuit of Figure 12)
Item Description Part Number Value
C1 Ceramic Capacitor TDK C4532X7R2A105M 1 µF, 100V
C2 Ceramic Capacitor TDK C4532X7R1E156M 15 µF, 25V
C3 Ceramic Capacitor Kemet C1206C104K5RAC 0.1 µF, 50V
C4 Ceramic Capacitor Kemet C1206C223K5RAC 0.022 µF, 50V
C5 Ceramic Capacitor TDK C3216X7R2A104M 0.1 µF, 100V
D1 Schottky Power Diode Diodes Inc. DFLS1100 100V, 1A
L1 Power Inductor TDK SLF7045T-151MR33 150 µH
R1 Resistor Vishay CRCW12063011F 3.01 kΩ
R2 Resistor Vishay CRCW12061001F 1.0 kΩ
R3 Resistor Vishay CRCW12063R00F 3.0 Ω
RON Resistor Vishay CRCW12062373F 237 kΩ
RCL Resistor Vishay CRCW12061693F 169 kΩ
U1 Switching Regulator LM5009
Figure 13. Efficiency vs Load Current and VIN Figure 14. Efficiency vs VIN and Load Current
Figure 15. VOUT vs Load Current Figure 16. Current Limit vs VIN
14 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM5009
LM5009
www.ti.com
SNVS402G –FEBRUARY 2006–REVISED FEBRUARY 2013
REVISION HISTORY
Changes from Revision F (February 2013) to Revision G Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 14
Copyright © 2006–2013, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Links: LM5009
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM5009MM NRND VSSOP DGK 8 1000 TBD Call TI Call TI -40 to 125 SLLB
LM5009MM/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SLLB
LM5009MMX NRND VSSOP DGK 8 3500 TBD Call TI Call TI -40 to 125 SLLB
LM5009MMX/NOPB ACTIVE VSSOP DGK 8 3500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 SLLB
LM5009SDC/NOPB ACTIVE WSON NGU 8 1000 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 5009SD
LM5009SDCX/NOPB ACTIVE WSON NGU 8 4500 Green (RoHS
& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 5009SD
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 2
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM5009SDC/NOPB WSON NGU 8 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1
LM5009SDCX/NOPB WSON NGU 8 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM5009SDC/NOPB WSON NGU 8 1000 210.0 185.0 35.0
LM5009SDCX/NOPB WSON NGU 8 4500 367.0 367.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 11-Oct-2013
Pack Materials-Page 2
MECHANICAL DATA
NGU0008B
www.ti.com
SDC08B (Rev A)
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