VCC

PGND

CNTRL

OUT

OUT_A

OUT_B

OUT_A

OUT_B

K1 * RSET

N-Channel Active Clamp

(RSET to REF)

P-Channel Active Clamp

(RSET to GND)

K2 * RSET

K1 * RSET

K2 * RSET

14

LM5025A

SNVS293F – DECEMBER 2004 – REVISED AUGUST 2016

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Copyright © 2004–2016, Texas Instruments Incorporated

Feature Description (continued)

Figure 10. PWM Outputs

7.3.4 Compound Gate Drivers

The LM5025A contains two unique compound gate drivers, which parallel both MOS and Bipolar devices to

provide high-drive current throughout the entire switching event. The bipolar device provides most of the drive

current capability and provides a relatively constant sink current which is ideal for driving large power MOSFETs.

As the switching event nears conclusion and the bipolar device saturates, the internal MOS device continues to

provide a low impedance to compete the switching event.

During turnoff at the Miller plateau region, typically around 2 V to 3 V, is where gate driver current capability is

needed most. The resistive characteristics of all MOS gate drivers are adequate for turnon because the supply to

output voltage differential is fairly large at the Miller region. During turnoff however, the voltage differential is

small and the current source characteristic of the bipolar gate driver is beneficial to provide fast drive capability.

Figure 11. Compound Gate Drivers

7.3.5 PWM Comparator

The PWM comparator compares the ramp signal (RAMP) to the loop error signal (COMP). This comparator is

optimized for speed to achieve minimum controllable duty cycles. The internal 5-kΩ pullup resistor, connected

between the internal 5-V reference and COMP, can be used as the pullup for an optocoupler. The comparator

polarity is such that 0 V on the COMP pin produces a zero duty cycle on both gate driver outputs.