Rainbow Electronics MAX1637 - Manual (Page 10)

MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
10 ______________________________________________________________________________________
PWM Controller Block
The heart of the current-mode PWM controller is a
multi-input, open-loop comparator that sums four sig-
nals: the output voltage error signal with respect to
the reference voltage, the current-sense signal, the
integrated voltage-feedback signal, and the slope-
compensation ramp (Figure 3). The PWM controller is
a direct-summing type, lacking a traditional error
amplifier and the phase shift associated with it. This
direct-summing configuration approaches ideal
cycle-by-cycle control over the output voltage.
SHOOT-
THROUGH
CONTROL
R
Q
30mV
R Q
LEVEL
SHIFT
1X
gm
2X
OSC
LEVEL
SHIFT
REF
CURRENT
LIMIT
SYNCHRONOUS
RECTIFIER CONTROL
SHDN
CK
-100mV
CSH
CSL
CC
REF
FB
BST
DH
LX
V GG
DL
PGND
S
S
SLOPE
COMPENSATION
SKIP
COUNTER
DAC
SOFT-START
Figure 3. PWM Controller Functional Diagram