LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

6

30251234fc

PIN FUNCTIONS

BIAS (Pin 1): BIAS Input Voltage. BIAS provides internal

power for LTC3025-X circuitry. The BIAS pin should be

locally bypassed to ground if the LTC3025-X is more than a

few inches away from another source of bulk capacitance.

In general, the output impedance of a battery rises with

frequency, so it is usually advisable to include an input

bypass capacitor in battery-powered circuits. A capacitor

in the range of 0.01μF to 0.1μF is usually sufficient.

GND (Pin 2): Ground. Connect to a ground plane.

IN (Pin 3): Input Supply Voltage. The output load current

is supplied directly from IN. The IN pin should be locally

bypassed to ground if the LTC3025-X is more than a few

inches away from another source of bulk capacitance. In

general, the output impedance of a battery rises with fre-

quency, so it is usually advisable to include an input bypass

capacitor when supplying IN from a battery. A capacitor

in the range of 0.1μF to 1μF is usually sufficient.

OUT (Pin 4): Regulated Output Voltage. The OUT pin

supplies power to the load. A minimum ceramic output

capacitor of at least 1μF is required to ensure stability.

Larger output capacitors may be required for applications

with large transient loads to limit peak voltage transients.

See the Applications Information section for more informa-

tion on output capacitance.

ADJ (Pin 5) LTC3025-1: Adjust Input. This is the input to

the error amplifier. The ADJ pin reference voltage is 0.4V

referenced to ground. The output voltage range is 0.4V to

3.6V and is typically set by connecting ADJ to a resistor

divider from OUT to GND. See Figure 2.

SENSE (Pin 5) LTC3025-2, LTC3025-3, LTC3025-4: Out-

put Sense. The sense is the input to the resistor divider

driving the error amplifier. Optimum regulation will be

obtained at the point where SENSE is connected to OUT.

The SENSE pin bias current is 10μA at the nominal rated

output voltage.

SHDN (Pin 6): Shutdown Input, Active Low. This pin is

used to put the LTC3025-X into shutdown. The SHDN pin

current is typically less than 10nA. The SHDN pin cannot

be left floating and must be tied to a valid logic level (such

as BIAS) if not used.

Exposed Pad (Pin 7): Ground and Heat Sink. Must be

soldered to PCB ground plane or large pad for optimal

thermal performance.

TYPICAL PERFORMANCE CHARACTERISTICS

Transient Response

250mA

10mA

AC

10mV/DIV

100μs/DIV

30251234 G13

1

0

0.025

0.075

0.100

0.125

0.300

0.175

2

3

3.5

30251234 G14

0.050

0.200

0.225

0.250

0.725

0.150

1.5

2.5

4

4.5

BIAS = 2.7V

BIAS = 3V

BIAS = 3.3V

BIAS = 3.8V

BIAS = 5V

1

0

0.025

0.075

0.100

0.125

0.300

0.175

2

3

3.5

30251234 G15

0.050

0.200

0.225

0.250

0.725

0.150

1.5

2.5

4

4.5

BIAS = 2.7V

BIAS = 3.8V

BIAS = 5V

BIAS = 3V

BIAS = 3.3V