AP5100_1011 Datasheet, PDF (3/10 Pages) Diodes Incorporated – 1.2A Step-Down Converter with 1.4MHz Switching Frequency

AP5100
1.2A Step-Down Converter with 1.4MHz Switching
Frequency
Pin Descriptions
Pin Name
BST
GND
FB
EN
IN
SW
Pin #
1
2
3
4
5
6
Description
Bootstrap. To form a boost circuit, a capacitor is connected between SW and BST pins to form a
floating supply across the power switch driver. This capacitor is needed to drive the power switch’s
gate above the supply voltage. Typical values for C_BST range from 0.1uF to 1uF.
Ground. This pin is the voltage reference for the regulated output voltage. All control circuits are
referenced to this pin. For this reason care must be taken in its layout.
Feedback. To set the output voltage, connect this pin to the output resistor divider or directly to
V_OUT. To prevent current limit run away during a current limit condition, the frequency foldback
comparator lowers the oscillator frequency when the FB voltage is below 400mV.
On/Off Control Input. Do not leave this pin floating. To turn the device ON, pull EN above 1.2V and
to turn it off pull below 0.4V.
If enable/disable is not used, connect a 100kOhm resistor between EN to V_IN.
Supply Voltage. The AP5100 operates from a +4.75V to +24V unregulated input. A decoupling
capacitor C1 is required to prevent large voltage spikes from appearing at the input. Place this
capacitor near the IC.
Switch Output. This is the reference for the floating top gate driver.
Functional Block Diagram
Figure 5. Functional Block Diagram
AP5100
Document number: DS32130 Rev. 2 - 2
3 of 10
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November 2010
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