RT2516 datasheet(7/9 Pages) RICHTEK

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RT2516

DS2516-01

July 2012

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Application Information

The RT2516 is a low voltage, low dropout linear regulator

with an external bias supply input capable of supporting

an input voltage range from 1.4V to 6V with a fixed output

voltage from 1V to 2V in 0.1V increments.

Output Voltage Setting

The RT2516 output voltage is adjustable from 1.4V to 6V

via the external resistive voltage divider. The voltage divider

resistors can have values of up to 800k

Ω because of the

very high impedance and low bias current of the sense

comparator. The output voltage is set according to the

following equation :

OUT

ADJ

= V

⎛⎞

×⎜⎟

⎝⎠

where VADJ is the reference voltage with a typical value of

0.5V.

Chip Enable Operation

The RT2516 goes into sleep mode when the EN pin is in

a logic low condition. In this condition, the pass transistor,

error amplifier, and band gap are all turned off, reducing

the supply current to only 10

μA (max.). The EN pin can

be directly tied to VIN to keep the part on.

Current Limit

The RT2516 contains an independent current limit circuitry,

which monitors and controls the pass transistor's gate

voltage, limiting the output current to 3A (typ.).

CIN and COUT Selection

Like any low dropout regulator, the external capacitors of

the RT2516 must be carefully selected for regulator stability

and performance. Using a capacitor of at least 10

μF is

suitable. The input capacitor must be located at a distance

of not more than 0.5 inch from the input pin of the IC. Any

good quality ceramic capacitor can be used. However, a

capacitor with larger value and lower ESR (Equivalent

Series Resistance) is recommended since it will provide

better PSRR and line transient response.

The RT2516 is designed specifically to work with low ESR

ceramic output capacitor for space saving and performance

consideration. Using a ceramic capacitor with capacitance

of at least 10

μF and ESR larger than 1mΩ on the RT2516

output ensures stability. Nevertheless, the RT2516 can

still work well with other types of output capacitors due to

its wide range of stable ESR. Figure 3 shows the allowable

ESR range as a function of load current for various output

capacitance. Output capacitors with larger capacitance can

reduce noise and improve load transient response,

stability, and PSRR. The output capacitor should be located

at a distance of not more than 0.5 inch from the output pin

of the RT2516.

Figure 3

Thermal Considerations

Thermal protection limits power dissipation in RT2516.

When the operation junction temperature exceeds 160

°C,

the OTP circuit starts the thermal shutdown function and

turns the pass element off. The pass element turns on

again after the junction temperature cools by 30

°C.

RT2516 output voltage will be closed to zero when output

short circuit occurs as shown in Figure 4. It can reduce

the IC temperature and provides maximum safety to end

users when output short circuit occurs.

Region of Stable COUT ESR vs. Load Current

0.001

0.01

0.1

100

0.0

0.3

0.5

0.8

1.0

Load Current (A)

VIN = 3.3V, VOUT = 2.5V, COUT = 10

μF / X7R

Unstable Range

Stable Range

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