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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 832

DUAL OUTPUT LOW NOISE LDO REGULATORS

LT3028

DESCRIPTION

Demonstration circuit 832 is a dual output and dual in-

put regulator consisting of two identical LDO linear regu-

lators, based on the LT3028 monolithic linear regulator.

Each independent input has a voltage range of 2.3V to

20V, with one output (Vout1) capable of delivering up to

500mA of output current, and the other output (Vout2)

capable of delivering up to 100mA of output current.

The DC supply current is typically only 50uA (for the

entire IC) at no load. The LT3028 comes in either a 16-

lead DFN package or TSSOP package, both of which

have an exposed pad on the bottom-side of the IC for

better thermal performance. The DC832 comes installed

with ceramic capacitors, because of the LT3028 ability of

maintaining stability with ceramic output capacitors.

There are ceramic bypass capacitors on each output for

extra low noise performance. These features make the

DC832 demo board an ideal circuit for use in battery-

powered, hand-held applications or noise sensitive ap-

plications.

Gerber files for this circuit are avail-

able. Call the LTC Factory.

QUICK START PROCEDURE

The DC832 is easy to set up to evaluate the perform-

ance of the LT3028. For a proper measurement

equipment configuration, set up the circuit according

to the diagram in Figure 1.

Please follow the procedure outlined below for proper

operation.

1. Connect the input power supply to the Vin and

GND terminals. Connect the loads between

the Vout and GND terminals. Refer to figure 1

for the proper measurement equipment setup.

2. Before proceeding to operation, insert jump-

ers JP1 and JP2 into the OFF positions, jump-

ers JP3 and JP4 into the voltage options of

choice (2.5V, 3.3V, and 5V).

3. Apply 6.5V at Vin. Measure both Vouts; they

should read 0V.

4. Turn on Vout1 and Vout2 by changing jump-

ers JP3 and JP4 from the OFF positions to the

ON positions. Both output voltages should be

within a tolerance of +/- 2%.

5. Vary the input voltage from 6.5V to 20V. Both

output voltages should be within +/- 3.3% tol-

erance.

6. Vary Vout1 load current from 0 to 500mA. Its

output voltages should be within a tolerance

of +/- 4%.

7. Vary Vout2 load current from 0 to 100mA. Its

output voltages should be within a tolerance

of +/- 4%.

8. Observe both output voltages AC-coupled;

they should measure noise voltages of less

than 5mVAC each. Refer to Figure 2 for

proper measurement technique.

9. When finished, insert jumpers JP1 and JP2 to

the OFF position(s) and disconnect the power.

Warning - If the power for the demo board is carried in

long leads, the input voltage at the part could “ring”,

which could affect the operation of the circuit or even

exceed the maximum voltage rating of the IC. To elimi-

nate the ringing, insert a small tantalum capacitor (for

instance, AVX part # TAJW106M025R) on the pads be-

tween the input power and return terminals on the bot-

tom of the demo board. The (greater) ESR of the tanta-

lum will dampen the (possible) ringing voltage due to

the use of long input leads. On a normal, typical PCB,

with short traces, the capacitor is not needed.