Rainbow Electronics MAX5071 - Manual (Page 11)

Detailed Description
The MAX5070/MAX5071 current-mode PWM controllers
are designed for use as the control and regulation core of
flyback or forward topology switching power supplies.
These devices incorporate an integrated low-side driver,
adjustable oscillator, error amplifier (MAX5070A/
MAX5070B only), current-sense amplifier, 5V reference,
and external synchronization capability (MAX5071A/
MAX5071B only). An internal +26.5V current-limited V
CC
clamp prevents overvoltage during startup.
Five different versions of the MAX5070/MAX5071 are
available. The MAX5070A/MAX5070B are the standard
versions with a feedback input (FB) and internal error
amplifier. The MAX5071A/MAX5071B include bidirection-
al synchronization (SYNC). This enables multiple
MAX5071A/MAX5071Bs to be connected and synchro-
nized to the device with the highest frequency. The
MAX5071C includes an ADV_CLK output, which pre-
cedes the MAX5071C’s drive output (OUT) by 110ns.
Figures 1, 2, and 3 show the internal functional diagrams
of the MAX5070A/MAX5070B, MAX5071A/MAX5071B,
and MAX5071C, respectively. The MAX5070A/
MAX5071A are capable of 100% maximum duty cycle.
The MAX5070B/MAX5071B/MAX5071C are designed to
limit the maximum duty cycle to 50%.
MAX5070/MAX5071
High-Performance, Single-Ended, Current-Mode
PWM Controllers
______________________________________________________________________________________ 11
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
VEA
3
5
2
1
CS
GND
FB
COMP
CLK
MAX5070A/MAX5070B
VP
2.5V
16V/10V
100% MAX DUTY CYCLE (MAX5070A)
50% MAX DUTY CYCLE (MAX5070B)
Figure 1. MAX5070A/MAX5070B Functional Diagram