BETAPIN 1 · Error amplifier
Inverting error inputINV
Function
A higher voltage than NI2 reduces the demand for output conduction.
How to connect
Connect to the midpoint of two 10 kΩ resistors from REF16 to GND in this pulse demonstration.
Alternating-output PWM controller
SG3525A Pinout
Explore SG3525A pins, signal names, electrical functions and connection guidance for each package.
Package view
16Physical pins
SG3525ANPDIP-16
Manufacturer-referencedSTMicroelectronics
Pin diagram
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SG3525ANPDIP-16Top view
SG3525APSO-16Top view
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PIN 2 · Error amplifier
Noninverting error inputNI
Function
A higher voltage than INV1 requests a longer pulse.
How to connect
Connect to REF16 for maximum pulse demand in the bench example.
Electrical note
The amplifier inputs are biased in the documented common-mode region, not left floating.
PIN 3 · Timing and protection controls
Oscillator synchronization inputSYNC
Function
External positive clock pulses can synchronize the oscillator.
How to connect
Tie to GND when not using external synchronization.
PIN 4 · Clock and driver outputs
Oscillator clock outputOSC OUT
Function
Clock at the oscillator rate, before alternating output steering.
How to connect
Leave open or use a high-impedance scope.
PIN 5 · RC oscillator
Timing capacitor nodeCT
Function
The oscillator charges and discharges this external capacitor.
How to connect
Connect 10 nF to GND and RD = 100 Ω to DISCHARGE7.
PIN 6 · RC oscillator
Timing resistor nodeRT
Function
Sets the oscillator charging current.
How to connect
Connect 10 kΩ to GND.
PIN 7 · RC oscillator
Timing discharge contactDISCHARGE
Function
The external resistance between this pin and CT sets extra discharge dead time.
How to connect
Connect 100 Ω between pins 7 and 5.
Electrical note
RD belongs between DISCHARGE and CT, not from pin 7 to ground.
PIN 8 · Timing and protection controls
Soft-start capacitor nodeSOFT START
Function
An internal current charges the capacitor and gradually releases the pulse-width limit.
How to connect
Connect 1 µF to GND, positive at pin 8 if polarized.
Electrical note
Shutdown and undervoltage lockout discharge this capacitor.
PIN 9 · Timing and protection controls
Error-amplifier compensationCOMP
Function
Error-amplifier output and PWM control node. External compensation shapes a real regulator loop.
How to connect
Leave externally unconnected for this fixed-demand scope example.
Electrical note
An external pull-down can suppress pulses; do not force a voltage against the amplifier output.
PIN 10 · Timing and protection controls
Active-HIGH shutdownSHUTDOWN
Function
A positive input turns both outputs off; a sustained command discharges soft start.
How to connect
Use 10 kΩ to GND and a normally open pushbutton to REF16.
Electrical note
Do not leave this pin floating.
PIN 11 · Clock and driver outputs
First alternating outputOUT A
Function
Totem-pole output driven from VC13. LOW is the OFF state.
How to connect
Use a high-impedance scope and an optional 10 kΩ load to GND.
PIN 12 · Ground
Common returnGND
Function
Return for the control supply, reference, oscillator and output drivers.
How to connect
Join supply bypass and timing returns close to this pin.
PIN 13 · Supply
Output-driver supplyVC
Function
Separate supply for the two output stages.
How to connect
Connect to +12 V with local 100 nF bypass in the bench circuit.
Electrical note
It is a supply input, not a switch output.
PIN 14 · Clock and driver outputs
Second alternating outputOUT B
Function
Receives alternate oscillator cycles relative to OUT A. LOW is the OFF state.
How to connect
Use the second scope channel and an optional 10 kΩ load to GND.
PIN 15 · Supply
Control supplyVI
Function
Powers the reference and internal control circuitry.
How to connect
Connect +12 V with 100 nF and local bulk decoupling.
PIN 16 · Bias reference
5.1 V referenceVREF
Function
Bias reference for low-current control networks.
How to connect
Bypass with 100 nF; feed NI2, the INV divider and the shutdown switch.
Electrical note
Use the SG3525A electrical table: initial output is specified 5.0–5.2 V.