PAM2421/ PAM2422/ PAM2423

Document number: DS36383 Rev. 2 - 2

7 of 10

www.diodes.com

January 2016

© Diodes Incorporated

PAM2421/ PAM2422/ PAM2423

Application Information

The PAM242x are highly efficient step-up DC/DC converters that employ a current mode, fixed frequency pulse-width modulation (PWM)

architecture with excellent line and load regulation.The PAM242x operate at constant switching frequency under medium to high load current

conditions. At light loads, these devices operate in a pulse-skipping mode in order to improve light-load efficiency.

Soft-Start

The PAM242x both offer a programmable soft-start function which minimizes inrush current during startup. The soft-start period is programmed

by connecting a 10nF capacitor between SS and Ground. Operation of the soft-start function is as follows: when the IC is disabled, SS is actively

discharged to Ground. Upon enabling the IC, CSS is charged with a 4.5µA current so that the voltage at SS increases in a controlled manner.

The peak inductor current is limited by the voltage at SS, so that the input current is limited until the soft-start period expires, and the regulator

can achieve its full output current rating.

Setting the Output Voltage

The both feature external adjustable output voltages of up to 24V. To program the output voltage, simply connect a resistive voltage divider

between the output, FB, and GND, with resistors set according to the following equation:

































1

V

V

x

2

R

1

R

FB

OUT

Rectifier Selection

For optimal performance, the rectifier should be a Schottky rectifier that is rated to handle both the output voltage as well as the peak switch

current.

Open Voltage Protection

The features internal automatic over-voltage protection, when feedback voltage is higher than 115%.

Open Protection

Once the outputs achieve regulation, if the voltage at FB falls below 0.2V the controller will automatically disable, preventing the controller from

running open-loop and potentially damaging the IC and load.

Shutdown

Drive EN low to disable the IC and reduce the supply current to just 0.1µA. As with all nonsynchronous step-up DC/DC converters, the external

Schottky diode provides a DC path from the input to the output in shutdown. As a result, the output drops to one diode voltage drop below the

input in shutdown.

The PAM242x both feature integrated thermal overload protection. Both devices are automatically disabled when their junction temperatures

exceed +160°C, and automatically re-enable when the die temperature decreases by 40°C.