Datasheet

UCC2895-Q1
www.ti.com SLUS783C –MAY 2008–REVISED AUGUST 2012
Output MOSFET Drivers (OUTA, OUTB, OUTC, OUTD)
The four outputs are 100-mA CMOS drivers and are optimized to drive MOSFET driver circuits. OUTA and
OUTB are fully complementary, assuming no programming delay. They operate near 50% duty cycle and one-
half the oscillator frequency. OUTA and OUTB are intended to drive one half-bridge circuit in an external power
stage. OUTC and OUTD drive the other half-bridge circuit and have the same characteristics as OUTA and
OUTB. OUTC is phase shifted with respect to OUTA, and OUTD is phase shifted with respect to OUTB.
NOTE
Changing the phase relationship of OUTC and OUTD with respect to OUTA and OUTB
requires other than the nominal 50% duty ratio on OUTC and OUTD during those
transients.
Power Ground (PGND)
To keep output switching noise from critical analog circuits, the UCC2895-Q1 has two different ground
connections. PGND is the ground connection for the high-current output stages. Both GND and PGND must be
electrically tied together. Also, because PGND carries high current, board traces must be low-impedance.
Inverting Input of the PWM Comparator (RAMP)
This pin receives either the CT waveform in voltage control and average-current-mode control or the current
signal (plus slope compensation) in peak-current-mode control.
Voltage Reference (REF)
The 5 V ± 1.2% reference supplies power to internal circuitry, and can also supply up to 5 mA to external loads.
The reference is shut down during undervoltage lockout (UVLO) but is operational during all other disable
modes. For best performance, bypass with a 0.1-μF low-ESR low-ESL capacitor to GND. Do not use more than
1 μF of total capacitance on this pin to ensure the stability of the internal reference.
Oscillator Timing Resistor (RT)
The oscillator operates by charging an external timing capacitor (C
T
) with a fixed current programmed by R
T
. R
T
current is calculated by Equation 4:
I
RT
(A) = 3 V / R
T
(Ω) (4) (4)
R
T
can range from 40 kΩ to 120 kΩ. Soft-start charging and discharging currents are also programmed by I
RT
(see Figure 1).
Analog Ground (GND)
This pin is the ground for all internal circuits except the output stages.
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