US1205

2-3

Rev. 1.4

9/25/00

PIN #

PIN SYMBOL

PIN DESCRIPTION

A resistor divider from this pin to the Vout pin and ground sets

the output voltage.

A 470 to 1000pF bypass capacitor connected to this pin re-

duces the output noise.

The output of the regulator .A minimum of 2.2uF with max

ESR of 1 ohm capacitor must be connected from this pin to

ground to insure stability.

Ground pin. This pin must be connected to the lowest poten-

tial in the system & all other pins must be at higher potential

with respect to this pin.

Enable pin. A low signal or left open on this pin shuts down the

output.This pin must be tied HI or to Vin for normal operation.

The input pin of the regulator. Typically a large storage capacitor

is connected from this pin to ground to insure that the input

voltage does not sag below the minimumdrop out voltage dur-

ing the load transient response. This pin must always be higher

than Vout by at least the amount of the dropout voltage and

some margin in order for the device to regulate properly.

4

Adj

(Adjustable only)

4

Byp

(Fixed output only)

5

Vout

2

GND

3

En

1

Vin

5 LEAD

Output

SOT 23

Voltage

US1205

1.242V

US1205-25

2.5 V

US1205-30

3.0 V

US1205-33

3.3 V

US1205-36

3.6 V

Table 1- Nominal output voltage v.s. part number

BLOCK DIAGRAM

BLOCK DIAGRAM

Note 3 : Ground current is the the regulator quiescent

current plus the pass transistor current. The total cur-

rent from the supply is the sum of the load current plus

the ground pin current.

Note 4 : The specification applies for the junction tem-

perature of 0 to +125

°C.

Note 1 : Low duty cycle pulse testing with Kelvin con-

nections are required in order to maintain accurate data.

Note 2 : Drop-out voltage is defined as the minimum

differential voltage between Vin and Vout required to main-

tain regulation at Vout. It is measured when the output

voltage drops 1% below its nominal value.

Vin

En

1205blk1-1.1

+

THERMAL

SHUTDOWN

1.242V

Vout

Adj

Gnd

Vin

En

1205blk2-1.0

+

THERMAL

SHUTDOWN

1.242V

Vout

Byp

Gnd

Figure 1- US1205 Adjustable block diagram

Figure 2- US1205 Fixed output block diagram

Pin DescRIPTIONS

Pin DescRIPTIONS

The output voltage of the adjustable device can be set using:

Where;

R1=Resistor connected from output to the Adj pin

R2=Resistor connected from Adj pin to GND