Specifications

44 Maxim Industrial Solutions
Programmable logic controllers (PLCs)
Isolated power-supply functions
Benefits
• Integrated protection circuitry prevents
system-level failures
– Thermal shutdown
– Undervoltage lockout (UVLO)
– Watchdog protection in clock circuitry
• Internal/external clocking modes allow
system performance to be optimized
– Integrated internal oscillator eliminates
the need for an external clock/oscillator
– External clock-synchronization mode
improves EMI performance
• Integrated push-pull drivers reduce
BOM complexity and board space
MAX256
For systems that require a low-watt, isolated power supply, a typical
closed-loop switching regulator can add unnecessary cost and
complexity. The MAX256 simplifies an isolated power-supply design.
It is easily used for implementing an unregulated, full-bridge forward
converter with an output power of up to 3W from an input voltage of
3V to 5.5V.
The device integrates 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 operates with an internal
programmable oscillator, or it can be driven by an external clock for
improved EMI performance. The MAX256 is available in an 8-pin,
thermally enhanced SO package. The device is specified for the
-40°C to +125°C automotive temperature range.
Simplify isolated power-supply design with a highly integrated transformer driver
GND
ST2
+5V ISOLATED
MAX256
47kΩ
4.7µF
ST1
MODE
CK_RS
0.1
µF
+5V
470nF
1:2.6CT
The MAX256 can be used in an unregulated 3W power supply.