Pin

Symbol

Function

Description

11

POR

Power-On

This open-collector output is driven low when either the supply voltage falls below the

Reset Flag

Undervoltage Lockout Threshold Voltage or the output voltage is less than the Power-

on Reset Threshold Voltage Leave the pin open if not used

12

Reset Delay Capacitor

Adding a capacitor between this pin and ground sets the power-on reset flag delay

time according to the following formula

F s X

Leave the pin open if not used The POR flag will still operate if this function is not

used

13

FB

Feedback Input

A sample of the output voltage via a resistor divider is fed back into this pin which is

the inverting input of the error amplifier

14

EAO

Error Amplifier Output

Error Amplifier Output The output can source 15 mA typically and sink 300 mA

typically This pin is primarily used for loop compensation

Note

Pins 1 2 4 5 and 10 are internally clamped by a 56V zener diode Do not force a voltage larger than 5V on these pins

without a resistor to limit the current to below 1 mA All other pins are limited to the supply voltage

Test Circuit

LM3101 specifications are measured using automated

test equipment This circuit is provided for the custom-

er’s convenience when checking parameters Due to

possible variations in testing conditions the measured

values from these testing procedures may not match

those of the factory

TLH11436 – 5

This test circuit is for exercising the LM3101 functions and

measuring its specifications

With the switch positions

shown the supply current should measure 15 mA (typical)

for a supply voltage of 15V Changing the supply voltage to

supply current 11 mA (typical) Changing SW7 to the supply

voltage will shutdown the LM3101 output

To test the oscillator section adjust the 5 kX potentiometer

mately 500 kHz Switch SW2 to obtain a 1 MHz frequency

(typical) The maximum duty cycle of 92% typically can also

FB) in the open position will change the oscillator frequency

to approximately 180 kHz

Switching the MC pin SW1 to ground and opening SW4

the CMI pin will put the device in current mode control To

measure the current sense time delay (typically 75 ns)

close SW5 (connected to the CMI pin) and open SW6

7