DocID15086 Rev 4 9/21
PM8834 Device description and operation
21
DocID15086 Rev 4 9/21
PM8834 Device description and operation
21
4 Device description and operation
The PM8834 is a dual low-side driver suitable for charging and discharging large capacitive
loads like MOSFETs or IGBTs used in power supplies and DC/DC modules. The PM8834
can sink and source 4 A on both low-side driver branches but a higher driving current can be
obtained by paralleling its outputs.
Even though this device has been designed to function with loads requiring high peak
current and fast switching time, the ultimate driving capability depends on the power
dissipation in the device which must be kept below the power dissipation capability of the
package. This aspect will be discussed in Section 5.2 on page 13.
For enhanced control of operations the PM8834 has been designed with dual independent
active-high enable pins (ENABLE_1 and ENABLE_2). Connecting these pins to the GND
pin will disable the corresponding low-side driver.
The PM8834 uses the VCC pin for supply and the GND pin for return.
The dual low-side driver has been designed to work with supply voltage in the range of 5 to
18 V.
For VCC voltages greater than the UVLO threshold (UVLOVCC), the PWM input keeps the
control of the driver operations, provided that the corresponding enable pin is active. Both
PWM_1 and PWM_2 are internally pulled down so, if left floating, the corresponding output
pins are discharged.
The PM8834, during VCC startup, keeps both low-side MOSFETs in an OFF state until the
UVLO threshold is reached.
The input pins (PWM_1, PWM_2, ENABLE_1 and ENABLE_2) are CMOS/TTL-compatible
and can also operate with voltages up to VCC.
The voltage level of the input pins is not allowed to be higher than VCC under any operating
condition.
4.1 Input stage
4.1.1 PWM inputs
The inputs of the PM8834 dual low-side driver are compatible to CMOS/TTL levels with the
capability to be pulled up to VCC.
The relationship between the input pins (PWM_1, PWM_2) and the corresponding PWM
output pins (OUT_1, OUT_2) is depicted in Figure 3. In the worst case, input levels above
2.5 V are recognized as high voltage and values below 0.8 V are recognized as low logic
values. Propagation delays for high-low (tD_HL) and low-high (tD_LH) and rise (tR) and fall
(tR) times have been designed to ensure operation in a fast-switching environment.
Matched propagation delay in the two branches of the PM8834 ensures symmetry in
operation and allows parallel output functionality.
Each PWM input features a 10 µA pull-down to turn off (default state) the external MOSFET
/ IGBT.