DESCRIPTIONThe SG1844/45 family of control ICs provides all the necessary features to implement off-line fixed frequency, currentmode switching power supplies with a minimum number of external components. Current-mode architecture demonstrates improved line regulation, improved load regulation, pulse-by pulse current limiting and inherent protection of the power supply output switch. The bandgap reference is trimmed to ±1% over temperature. Oscillator discharge current is trimmed to less than ±10%. The SG1844/45 has undervoltage lockout, current-limiting circuitry and start-up current of less than 1mA. The totem-pole output is optimized to drive the gate of a power MOSFET.

KEY FEATURES■ OPTIMIZED FOR OFF-LINE CONTROL
■ LOW START-UP CURRENT (<1mA)
■ AUTOMATIC FEED FORWARD COMPENSATION
■ TRIMMED OSCILLATOR DISCHARGE CURRENT
■ PULSE-BY-PULSE CURRENT LIMITING
■ ENHANCED LOAD RESPONSE
■ CHARACTERISTICS
■ UNDER-VOLTAGE LOCKOUT WITH 6V HYSTERESIS (SG1844 only)
■ DOUBLE PULSE SUPPRESSION
■ HIGH-CURRENT TOTEM-POLE OUTPUT
■ INTERNALLY TRIMMED BANDGAP REFERENCE
■ 500kHz OPERATION
■ UNDERVOLTAGE LOCKOUT SG1844 - 16 volts SG1845 - 8.4 volts
■ LOW SHOOT-THROUGH CURRENT <75mA OVER TEMPERATURE

Manufacturer	Microchip Technology
Product Category	AC DC Converters, Offline Switchers
Series	-
Packaging	Tube
Package-Case	-
Operating-Temperature	-25°C ~ 85°C (TA)
Mounting-Type	Surface Mount
Supplier-Device-Package	8-SOIC
Watt	-
Output-Isolation	Isolated
Internal-Switch-s	No
Voltage-Breakdown	-
Topology	-
Voltage-Start-Up	16V
Voltage-Supply-Vcc-Vdd	10 V ~ 30 V
Duty-Cycle	48%
Frequency-Switching	100Hz ~ 500kHz
Fault-Protection	Current Limiting
Control-Features	Frequency Control