TC1305(2001) View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC1305
(Rev.:2001)

Dual 150mA CMOS LDO With SelectMode™ , Shutdown and Independent RESET Output

Microchip Technology 

TC1305

Dual 150mA CMOS LDO With Select

ModeTM, Shutdown and Independent

RESET Output

DETAILED DESCRIPTION

The TC1305 is a precision fixed output voltage regulator

that contains two fully independent 150mA regulator out-

puts. The device features seperate shutdown modes for

low-power operation, and a common bypass pin that can be

used to further reduce output noise. The SelectModeTM

allows the user to select VOUT1 and VOUT2 from three

different values (2.5V, 2.8V, 3.0V), therefore providing high

design flexibility. The CMOS construction of the TC1305

results to a very low supply current, which does not increase

with load changes. In addition, VOUT remains stable and

within regulation at very low load currents.

The TC1305 also features an integrated microproces-

sor supervisor that monitors power-up, power-down, and

brown-out conditions. The active low RESET signal is as-

serted when the detected voltage VDET falls below the reset

voltage threshold (2.63V). The RESET output remains low

for 300msec (typical) after VDET rises above the reset

threshold. The RESET output of the TC1305 is guaranteed

valid down to VDET=1V and is optimized to reject fast

transient glitches on the moinitored power supply line.

APPLICATION INFORMATION

Input and Output Capacitor

The TC1305 is stable with a wide range of capacitor

values and types. A capacitor with a minimum value of 1µF

from VOUT to Ground is required. The output capacitor

should have an effective series resistance (ESR) of 5Ω or

less. A 1µF capacitor should be connected from the VIN to

GND if there is more than 10 inches of wire between the

regulator and the AC filter capacitor, or if a battery is used as

the power source. Aluminum electrolytic or tantalum capaci-

tor types can be used. (Since many aluminum electrolytic

capacitors freeze at approximately – 30°C, solid tantalums

are recommended for applications operating between

–20°C). When operating from sources other than batteries,

supply-noise rejection and transient response can be im-

proved by increasing the value of the input and output

capacitors and employing passive filtering techniques.

Shutdown Mode

Applying a logic high to each of the shutdown pins turns

on the corresponding output. Each regulator enters shut-

down mode when a logic low is applied in the corresponding

input. During shutdown mode, output voltage falls to zero,

and regulator supply current is reduced to 0.5µA (max). If

shutdown mode is not necessary, the pins should be con-

nected to VIN.

SelectModeTM

The SelectModeTM is a tri-state input that allows the

user to select VOUT1 and VOUT2 from three different values.

By connecting the SELECT pin to GND, both output volt-

ages (VOUT1, VOUT2) supply 2.5V. Connecting the

SELECT pin to VIN results to both output channels supplying

a fixed 3.0V output. Last but not least, leaving the SELECT

pin floating sets both voltages to 2.8V. This output voltage

functionality provides high design flexibility and minimizes

costs associated with inventory, time-to-market and new

devices’ qualifications.

RESET Output

The microprocessor supervisor of the TC1305 provides

accurate supply voltage monitoring and reset timing during

power-up, power-down and brown-out conditions. The

RESET output is valid to VDET=1.0V (below this point it

becomes an open circuit and does not sink current) and is

able to reject negative going transients (glitches) on the

power supply line. Transient immunity can further be im-

proved by adding a capacitor close to the VDET pin of the

TC1305.

Bypass Capacitor

A 470pF capacitor connected from the Bypass input to

ground reduces noise present on the internal reference,

which in turn significantly reduces output noise. If output

noise is not a concern, this input may be left unconnected.

Larger capacitor values may be used, but result in a

longer time period to rated output voltage when power is

initially applied.

TC1305-1 12/22/00

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© 2001 Microchip Technology Inc. DS21526A

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