Datasheet

V
CC
PGND
CNTRL
OUT
OUT_A
OUT_B
OUT_A
OUT_B
K1 * R
SET
N-Channel Active Clamp
(R
SET
to REF)
P-Channel Active Clamp
(R
SET
to GND)
K2 * R
SET
K1 * R
SET
K2 * R
SET
LM5025
www.ti.com SNVS265B –DECEMBER 2003–REVISED MARCH 2013
Overlap Time (ns) = 2.8 x R
SET
- 1.2
Dead Time (ns) = 2.9 x R
SET
+20
R
SET
in kΩ, Time in ns
Figure 13. PWM Outputs
Compound Gate Drivers
The LM5025 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 turn-off at the Miller plateau region, typically around 2V - 3V, is where gate driver current capability is
needed most. The resistive characteristics of all MOS gate drivers are adequate for turn-on since the supply to
output voltage differential is fairly large at the Miller region. During turn-off however, the voltage differential is
small and the current source characteristic of the Bipolar gate driver is beneficial to provide fast drive capability.
Figure 14. Compound Gate Drivers
PWM Comparator
The PWM comparator compares the ramp signal (RAMP) to the loop error signal (COMP). This comparator is
optimized for speed in order to achieve minimum controllable duty cycles. The internal 5kΩ pull-up resistor,
connected between the internal 5V reference and COMP, can be used as the pull-up for an optocoupler. The
comparator polarity is such that 0V on the COMP pin will produce a zero duty cycle on both gate driver outputs.
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