MAX256_12 Datasheet, PDF (1/14 Pages) Maxim Integrated Products – 3W Primary-Side Transformer H-Bridge Driver for Isolated Supplies

19-3748; Rev 1; 3/12
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
o Provides Up to 3W to the Transformer in Isolated
Power Supplies
o Single Supply +5V or +3.3V Operation
o Internal Resistor-Programmable Oscillator Mode
o External Clock Mode with Watchdog
o Disable Mode
o Undervoltage Lockout
o Thermal Shutdown
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX256ASA+
MAX256ASA/V+T
-40°C to +125°C
-40°C to +125°C
8 SO-EP*
8 SO-EP*
*EP = Exposed paddle.
*/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
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
SO-EP
8 ST1
7 GND
6 GND
5 ST2
*CONNECT EXPOSED PAD 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.