DC250A-A - ANALOG DEVICES - Datasheet.Live

DC250A Quick Start Guide

The DC250A demonstration board contains all of the circuitry needed for evaluation of the

LTC1503CMS8-1.8/2 inductorless switching regulator IC. To begin, simply connect an input

power supply to VIN (E3) and GND (E4) (see Figure 1). Connect the load between VOUT (E2) and

GND (E4). Once power is applied, the LTC1503CMS-1.8/2 will start up automatically and produce

a regulated 1.8V/2V output voltage.

With an input supply of between 2.4V and 6V, the output will regulate correctly for any load

current up to 100mA. Accidental short circuits from VOUT to GND will not damage the

LTC1503CMS8-1.8/2 or DC250A demonstration board.

To place the LTC1503CMS8-1.8/2 in shutdown, simply connect the SHDN/SS pin (E5) to GND

(E4). To re-start the LTC1503CMS8-1.8/2 remove the ground connection from SHDN/SS. The IC

will automatically pull up on the SHDN/SS pin and regulate to the correct voltage at its output.

Inrush current can be controlled by the use of jumper JP1. If JP1 is in place, soft-start capacitor C3

is connected to the SHDN/SS pin. C3 limits the inrush current by limiting the dV/dt of the output

voltage upon start-up. Without JP1, the LTC1503CMS8-1.8/2 will deliver current to COUT, the

output capacitor, as quickly as possible until the regulation voltage is reached.

To evaluate the soft-start feature of the LTC1503CMS8-1.8/2 an open-drain output from a

microcontroller or a discrete transistor can be connected to the SHDN/SS pin (E5). For example,

using a discrete transistor, connect the drain of the device to SHDN/SS (E5) and the source to GND

(E4). The gate can be manipulated to a suitable control voltage or pulsed waveform with a function

generator. To see the soft start characteristics on an oscilloscope, a load resistor will be needed to

discharge the output capacitor. A 33ohm resistor will discharge the 10µF output capacitor in about

1ms.

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