Datasheet

MAX8792
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
______________________________________________________________________________________ 13
Free-Running Constant-On-Time PWM
Controller with Input Feed-Forward
The Quick-PWM control architecture is a pseudo-fixed-
frequency, constant on-time, current-mode regulator
with voltage feed-forward (Figure 2). This architecture
relies on the output filter capacitor’s ESR to act as a cur-
rent-sense resistor, so the output ripple voltage provides
the PWM ramp signal. The control algorithm is simple:
the high-side switch on-time is determined solely by a
one-shot whose pulse width is inversely proportional to
DYNAMIC OUTPUT
TRANSITION DETECTION
BST
LX
ONE-SHOT
TRIG
Q
t
OFF(MIN)
ON-TIME
COMPUTE
FB
TON
ERROR
AMPLIFIER
EA + 0.3V
ONE-SHOT
TRIG Q
t
ON
ZERO CROSSING
FB
EA
PGOOD
EN
PGOOD
AND FAULT
PROTECTION
SKIP
EA - 0.2V
BLANK
REFIN
VALLEY CURRENT LIMIT
GND
S
R
Q
S
R
Q
DH
IN
SOFT-
START/STOP
QUAD-
LEVEL
DECODE
BLANK
DL
V
CC
V
DD
2V
REF
FAULT
INTEGRATOR
(CCV)
REF
ILIM
MAX8792
Figure 2. MAX8792 Functional Diagram