REGULATING PULSE WIDTH MODULATOR

FEATURES

••••• 8V to 35V operation

••••• 5.1V reference trimmed to ±1%

••••• 100Hz to 500KHz oscillator range

••••• Separate oscillator sync terminal

••••• Adjustable deadtime control

••••• Internal soft-start

••••• Input undervoltage lockout

••••• Latching P.W.M. to prevent multiple

pulses

••••• Dual source/sink output drivers

HIGH RELIABILITY FEATURES

- SG1525A, SG1527A

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♦ Available to MIL-STD-883B

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♦ MIL-M38510/12602BEA - JAN1525AJ

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♦ MIL-M38510/12604BEA - JAN1527AJ

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♦ Radiation data available

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♦ LMI level "S" processing available

DESCRIPTION

The SG1525A/1527A series of pulse width modulator integrated circuits are

designed to offer improved performance and lower external parts count when used

to implement all types of switching power supplies. The on-chip +5.1 volt reference

is trimmed to ±1% initial accuracy and the input common-mode range of the error

amplifier includes the reference voltage, eliminating external potentiometers and

divider resistors. A Sync input to the oscillator allows multiple units to be slaved

together, or a single unit to be synchronized to an external system clock. A single

resistor between the C

adjustment. These devices also feature built-in soft-start circuitry with only a timing

capacitor required externally. A Shutdown pin controls both the soft-start circuitry

and the output stages, providing instantaneous turn-off with soft-start recycle for

slow turn-on. These functions are also controlled by an undervoltage lockout which

keeps the outputs off and the soft-start capacitor discharged for input voltages less

than that required for normal operation. Another unique feature of these PWM

circuits is a latch following the comparator. Once a PWM pulse has been terminated

for any reason, the outputs will remain off for the duration of the period. The latch

is reset with each clock pulse. The output stages are totem-pole designs capable

of sourcing or sinking in excess of 200mA. The SG1525A output stage features

NOR logic, giving a LOW output for an OFF state. The SG1527A utilizes OR logic

which results in a HIGH output level when OFF.

BLOCK DIAGRAM

SG1525A/SG2525A/SG3525A

SG1527A/SG2527A/SG3527A

Rev 1.4a 3/19/2005

Microsemi Inc.

Copyright

© 1996

11861 Western Avenue

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(714) 898-8121

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