TC1305 datasheet(5/18 Pages) MICROCHIP

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DS21526A-page 5

TC1305

3.0

DETAILED DESCRIPTION

The TC1305 is a precision fixed output voltage

regulator that contains two fully independent 150mA

regulator outputs. The device

features separate

shutdown modes for low-power operation, and a

common bypass pin that can be used to further reduce

output noise. The Select Mode™ operation 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 no 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 asserted 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 ensured valid down to VDET = 1V and is

optimized to reject fast transient glitches on the

monitored power supply line.

4.0

TYPICAL APPLICATIONS

4.1

Input and Output Capacitor

The TC1305 is stable with a wide range of capacitor

values and types. A capacitor with a minimum value of

µFfrom VOUT to Ground is required. The output

capacitor should have an effective series resistance

(ESR) of 0.1

Ω to 10Ω for a 1µF capacitor and 0.01Ω to

Ω for a 10µF capacitor. 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 capacitor types can

be used. (Since many aluminum electrolytic capacitors

freeze at approximately -30°C, solid tantalums are

recommended for applications operating below -20°C).

When operating from sources other than batteries,

supply-noise rejection and transient response can be

improved by increasing the value of the input and

output capacitors and employing passive filtering

techniques.

4.2

Bypass Capacitor

A0.01

µF capacitor connected from the bypass input to

ground

reduces

noise

present

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.

4.3

Shutdown Mode

Applying a logic high to each of the shutdown pins turns

on the corresponding output. Each regulator enters

shutdown mode when a logic low is applied in the

corresponding input. During shutdown mode, the out-

put voltage falls to zero, and regulator supply current is

reducedto0.5

µA (max). If shutdown mode is not

necessary, the pins should be connected to VIN.

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