1.2A Step-Down Converter with 1.4MHz Switching
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 CBST
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 VOUT. To prevent current limit run away during a current limit condition, the
frequency foldback comparator lowers the oscillator frequency when the FB voltage is
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 VIN.
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.
Absolute Maximum Ratings (Note 3)
ESD HBM Human Body Model ESD Protection
Machine Model ESD Protection
All Other Pins
TST Storage Temperature
TJ Junction Temperature
TL Lead Temperature
θJA Junction to Ambient Thermal Resistance (Note 4)
θJC Junction to Case Thermal Resistance (Note 4)
Notes: 3. Exceeding these ratings may damage the device.
4. Test condition for SOT26: Measured on approximately 1” square of 1 oz copper.
-0.3 to VIN + 0.3
VSW + 6
–0.3 to +6
-65 to +150
Document number: DS32130 Rev. 1 - 2
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