MAX256_05 Datasheet, PDF (1/14 Pages) Maxim Integrated Products – 3W Primary-Side Transformer H-Bridge Driver for Isolated Supplies

19-3748; Rev 0; 8/05
EVAALVUAAILTAIOBNLEKIT
3W Primary-Side Transformer H-Bridge Driver
for Isolated Supplies
General Description
The MAX256 is an integrated primary-side controller
and H-bridge driver for isolated power-supply circuits.
The device contains an on-board oscillator, protection
circuitry and internal FET drivers to provide up to 3W of
power to the primary winding of a transformer. The
MAX256 can be operated using the internal program-
mable oscillator or can be driven by an external clock
for improved EMI performance. Regardless of the clock
source being used, an internal flip-flop stage guaran-
tees a fixed 50% duty cycle to prevent DC current flow
in the transformer.
The MAX256 operates from a single-supply voltage of
+5V or +3.3V, and includes undervoltage lockout for
controlled startup. The device prevents cross-conduc-
tion of the H-bridge MOSFETs by implementing break-
before-make switching. Thermal shutdown circuitry
provides additional protection against damage due to
overtemperature conditions.
The MAX256 is available in the 8-pin thermally-enhanced
SO package. The device is specified for the automotive
(-40°C to +125°C) temperature range.
Applications
Isolated Power Supplies
Industrial Process
Control
Isolated Communications
Links
Medical Equipment
Telecommunications
Features
♦ Provides Up to 3W to the Transformer in Isolated
Power Supplies
♦ Single Supply +5V or +3.3V Operation
♦ Internal Resistor-Programmable Oscillator Mode
♦ External Clock Mode with Watchdog
♦ Disable Mode
♦ Undervoltage Lockout
♦ Thermal Shutdown
Ordering Information
PART
TEMP RANGE
MAX256ASA -40°C to +125°C
*EP = Exposed paddle.
PIN-PACKAGE
8 SO-EP*
PKG
CODE
S8E-12
Typical Application Circuit
Pin Configuration
4.7µF
47kΩ
470nF
+5V
1:2.6CT
MAX256 ^ST1
MODE
CK_RS
ST2
GND
+5V ISOLATED
0.1µF
+5V TO ISOLATED +5V TYPICAL APPLICATION
CK_RS 1
V_CC 2
MAX256
V_CC 3
MODE 4 ^EP*
8 ST1
7 GND
6 GND
5 ST2
SO-EP
*EXPOSED PAD IS CONNECTED TO GND
________________________________________________________________ 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.