TC1017 datasheet(11/28 Pages) MICROCHIP

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DS20001813G-page 11

TC1017

4.1

Input Capacitor

Low input source impedance is necessary for the LDO

to operate properly. When operating from batteries, or

in applications with long lead length (> 10") between

the input source and the LDO, some input capacitance

is required. A minimum of 0.1 µF is recommended for

most applications and the capacitor should be placed

as close to the input of the LDO as is practical. Larger

input capacitors will help reduce the input impedance

and further reduce any high-frequency noise on the

input and output of the LDO.

4.2

Output Capacitor

A minimum output capacitance of 1 µF for the TC1017

is required for stability. The Equivalent Series

Resistance (ESR) requirements on the output

capacitor are between 0 and 2 ohms. The output

capacitor should be located as close to the LDO output

as is practical. Ceramic materials X7R and X5R have

low temperature coefficients and are well within the

acceptable ESR range required. A typical 1 µF X5R

0805 capacitor has an ESR of 50 milli-ohms. Larger

output capacitors can be used with the TC1017 to

improve dynamic behavior and input ripple-rejection

performance.

Ceramic, aluminum electrolytic or tantalum capacitor

types can be used. Since many aluminum electrolytic

capacitors freeze at approximately -30

C, ceramic or

solid tantalums are recommended for applications

operating below -25

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.

4.3

Turn-On Response

The turn-on response is defined as two separate

response categories, wake-up time (tWK) and settling

time (tS).

The TC1017 has a fast wake-up time (10 µsec, typical)

when released from shutdown. See Figure 4-3 for the

wake-up time designated as tWK. The wake-up time is

defined as the time it takes for the output to rise to 2%

of the VOUT value after being released from shutdown.

The total turn-on response is defined as the settling

time (t

S) (see Figure 4-3). Settling time (inclusive with

tWK) is defined as the condition when the output is

within 98% of its fully-enabled value (32 µsec, typical)

when released from shutdown. The settling time of the

output voltage is dependent on load conditions and

output capacitance on VOUT (RC response).

The table below demonstrates the typical turn-on

response timing for different input voltage power-up

frequencies: VOUT = 2.85V, VIN = 5.0V, IOUT = 60 mA

and COUT = 1 µF.

FIGURE 4-3:

Wake-Up Time from Shutdown.

Frequency

Typical (tWK)

Typical (tS)

1000 Hz

5.3 µsec

14 µsec

500 Hz

5.9 µsec

16 µsec

100 Hz

9.8 µsec

32 µsec

50 Hz

14.5 µsec

52 µsec

10 Hz

17.2 µsec

77 µsec

VIH

tWK

VOUT

98%

VIL

SHDN

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