19-2115; Rev 0; 7/01
Current-Mode PWM Controllers with Integrated
Startup Circuit
General Description
The MAX5019/MAX5020 integrate all the building
blocks necessary for implementing DC-DC fixed-fre-
quency power supplies. Either primary- or secondary-
side regulation may be used to implement isolated or
nonisolated power supplies. These devices are current-
mode controllers with an integrated high-voltage start-
up circuit suitable for telecom/industrial voltage range
power supplies. Current-mode control with leading-
edge blanking simplifies control-loop design and inter-
nal ramp compensation circuitry stabilizes the current
loop when operating at duty cycles above 50%
(MAX5019). The MAX5019 allows 85% operating duty
cycle and can be used to implement flyback converters
whereas the MAX5020 limits the operating duty cycle to
less than 50% and can be used in single-ended for-
ward converters. A high-voltage startup circuit allows
these devices to draw power directly from the 18V to
110V input supply during startup. The switching fre-
quency is internally trimmed to 275kHz 卤10%, thus
reducing magnetics and filter component costs.
The MAX5019/MAX5020 are available in 8-pin SO
packages.
Warning:
The MAX5019/MAX5020 operate with high
voltages. Exercise caution.
Features
o
Wide Input Range: (18V to 110V) or (13V to 36V)
o
Isolated (without optocoupler) or Nonisolated
Power Supply
o
Current-Mode Control
o
Leading-Edge Blanking
o
Internally Trimmed 275kHz 卤10% Oscillator
o
Low External Component Count
o
Soft-Start
o
High-Voltage Startup Circuit
o
Pulse-by-Pulse Current Limiting
o
Thermal Shutdown
o
SO-8 Package
MAX5019/MAX5020
Ordering Information
PART
MAX5019CSA*
MAX5019ESA*
MAX5020CSA*
MAX5020ESA*
TEMP. RANGE
0掳C to +70掳C
-40掳C to +85掳C
0掳C to +70掳C
-40掳C to +85掳C
PIN-PACKAGE
8-SO
8-SO
8-SO
8-SO
Applications
Telecom Power Supplies
Industrial Power Supplies
Networking Power Supplies
Isolated Power Supplies
*See Selector Guide at end of data sheet.
Typical Operating Circuit
Pin Configuration
V
IN
V
OUT
V
DD
V+
TOP VIEW
MAX5020
V+
1
V
DD
2
FB
3
8
7
V
CC
NDRV
GND
V
CC
NDRV
CS
MAX5019/
MAX5020
6
5
SS_SHDN
GND
FB
SS_SHDN
4
CS
8-SO
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim鈥檚 website at www.maxim-ic.com.