19-2830; Rev 0; 4/03
Synchronizable, High-Frequency Current- and
Voltage-Mode PWM Controllers for Isolated Supplies
General Description
Features
ꢀ 200kHz to 1MHz Adjustable Switching Frequency
ꢀ Synchronization to External Clock
The MAX8540/MAX8541 pulse-width-modulated (PWM)
controllers for forward/flyback isolated DC-to-DC convert-
ers provide maximum flexibility to power-supply design-
ers and reduce external component count. These
controllers allow common PC board layout for current-
mode (MAX8540) and voltage-mode (MAX8541) designs.
ꢀ Programmable, Constant Maximum Volt-Second
Simplifies Transformer Design
ꢀ Programmable Hiccup/Skip Cycles or Latch-Mode
Both controllers feature adjustable switching frequency
and external synchronization from 200kHz to 1MHz.
Active-high and active-low enable, undervoltage pro-
tection (UVP), and overvoltage protection (OVP) reduce
external component count.
Protection
ꢀ Clean Startups with High-Capacitance Loads
ꢀ Programmable Under/Overvoltage Protection
ꢀ Current-Mode, Adjustable Slope Compensation
Maximum duty cycle is adjustable, and the feed-forward
function scales the maximum duty cycle with input volt-
age to limit the maximum volt-seconds applied to the
transformer primary. The MAX8540 allows the user to
select the value of slope compensation to further opti-
mize magnetics design. The MAX8541 features user-
adjustable ramp magnitude for the PWM comparator.
(MAX8540)
ꢀ Voltage-Mode, Adjustable Ramp Magnitude
(MAX8541)
ꢀ 10mA, 5V Regulator
ꢀ 75mV to 1.25mV Adjustable Current Limit
A cycle-by-cycle current-limit function controls the peak
primary current during overload and short circuit. Both
controllers can be set to latch off or to hiccup when a
short circuit is detected. The number of current-limited
cycles to initiate the hiccup mode and number of
cycles skipped are user selectable to allow startup with
high-capacitance loads and protect the converter
against sustained short circuits.
Reduces External Components
ꢀ Internal Gate Driver for Low-Power Applications
ꢀ External Gate Driver for High-Power Applications
Ordering Information
The MAX8540/MAX8541 feature 9Ω internal gate dri-
vers for low-power applications and are compatible
with external gate drivers for high-power applications.
Both devices are available in the space-saving 16-pin
QSOP package.
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
MAX8540EEE
MAX8541EEE
16 QSOP
The MAX8541 EV kit evaluates the MAX8540 and the
MAX8541 to speed designs. Design examples are also
available in application notes: 50W Voltage-Mode
Forward Converter Design with the MAX8541 and 50W
Current-Mode Forward Converter Design with the
MAX8540.
Pin Configurations
TOP VIEW
REF
1
2
3
4
5
6
7
8
16 V
CC
Applications
OV
UV
15 DRV
Isolated DC-to-DC Modules (Bricks)
14 GND
13 SKTON
12 CS
Cellular Base Stations
MAX8540EEE
FREQ/SYNC
SS
Telecom and Network Systems
High-Performance Off-Line AC/DC Converters
MAXDTY
EN
11 SKTOFF
10 ILIM
SCOMP
9
OPTO
QSOP
Functional Diagrams and Typical Operating Circuit appear
at end of data sheet.
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.