Rainbow Electronics MAX5071 - Manual (Page 12)

MAX5070/MAX5071
Current-Mode Control Loop
The advantages of current-mode control over voltage-
mode control are twofold. First, there is the feed-forward
characteristic brought on by the controller’s ability to
adjust for variations in the input voltage on a cycle-by-
cycle basis. Secondly, the stability requirements of the
current-mode controller are reduced to that of a single-
pole system unlike the double pole in the voltage-mode
control scheme.
The MAX5070/MAX5071 use a current-mode control loop
where the output of the error amplifier is compared to the
current-sense voltage (V
CS ). When the current-sense sig-
nal is lower than the noninverting input of the PWM com-
parator, the output of the CPWM comparator is low and
the switch is turned on at each clock pulse. When the
current-sense signal is higher than the inverting input of
the CPWM, the output of the CPWM comparator is high
and the switch is turned off.
High-Performance, Single-Ended, Current-Mode
PWM Controllers
12 ______________________________________________________________________________________
UVLO
REFERENCE
2.5V
PREREGULATOR
5V
VOLTAGE-
DIVIDER
THERMAL
SHUTDOWN
EN-REF
BG
SNS
V DD
5V REGULATOR
VOLTAGE-
DIVIDER
8
7
26.5V
V CC
VREF
2.5V
VP
REG_OK
DELAY
S
R
Q
OSC Q
4 R T /C T
6 OUT
ILIM
CPWM
1V
EN-DRV-BAR
R
2R
3
5
1
2
CS
GND
COMP
SYNC
CLK
MAX5071A/MAX5071B
VP
2.5V
1V
BIDIRECTIONAL
SYNC
100% MAX DUTY CYCLE (MAX5071A)
50% MAX DUTY CYCLE (MAX5071B)
16V/10V
Figure 2. MAX5071A/MAX5071B Functional Diagram