AP3101 datasheet(7/12 Pages) DIODES

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AP3101

Document number: DS37418 Rev. 2 - 2

7 of 12

www.diodes.com

July 2014

AP3101

A Product Line of

Diodes Incorporated

Performance Characteristics (Cont.)

Skip Level vs. Ambient Temperature

Oscillator Frequency vs. Timing Resistor

-40

-20

100

120

1.14

1.16

1.18

1.20

1.22

1.24

1.26

Ambient Temperature (

oC)

105

120

135

Timing Resistor (k)

Operation Description

The AP3101 is specially designed for off-line AC-DC adapter and battery charger applications. It offers the designer a cost effective solution with

minimal external components.

Oscillator

The oscillation frequency is programmed by the value of resistor R1 connected from pin RI to ground. The resistor will make a constant current

source to determine the oscillation frequency by charging and discharging an internal capacitor. The oscillation frequency can be expressed as:

)

kHz

(

)

(

1690





The recommended oscillation frequency is 50 to 100kHz.

Start-up Current and Operating Current

The typical start-up current is only 30

μA. With such a low start-up current, the start-up resistor may have a very high resistance value even in

85V line voltage; however, higher resistance will cause longer start-up time. So we must select a proper start-up resistor and a proper VCC hold-

up capacitor. Operating current is lowered to 3mA. It can reduce the requirement of VCC hold-up capacitor value and the power loss in AP3101.

Under-Voltage Lockout (UVLO)

An UVLO comparator is included in AP3101 to detect the voltage on the VCC pin. It ensures AP3101 to draw adequate energy from hold-up

capacitor during power on. The turn-on threshold is 16V and the turn-off threshold is 10V.

Current Sense Comparator and PWM Latch

AP3101 operates as a current mode controller, the output switch conduction is initiated by every oscillator cycle and terminated when the peak

inductor current reaches the threshold level established by the FB pin. The inductor current signal is converted to a voltage signal by inserting a

referenced sense resistor RS in series with the source of the MOSFET. The peak inductor current under normal operating conditions is controlled

by the voltage at FB pin:

)

(





Abnormal operating conditions occur when the power supply output is overloaded or the output voltage sensing is lost. Under these conditions,

the current sense comparator threshold will be internally clamped to 0.85V. Therefore the maximum peak switch current is:

(max)



AP3101 Datasheet(PDF) 7 Page - Diodes Incorporated

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