NCP729

http://onsemi.com

11

APPLICATIONS INFORMATION

General

The NCP729 is a high performance 200 mA Very Low

Dropout Linear Regulator. This device delivers excellent

noise and dynamic performance. It features typical

quiescent current of 35

mA at no−load, ultra−low noise of

10

dynamic parameters and small package size make the device

an ideal choice for powering the precision analog and noise

sensitive circuitry in portable applications. NCP729

requires very small voltage headroom for correct operation.

The dropout for 3.3 V voltage option is only 68 mV (typ.) A

logic EN input provides ON/OFF control of the output

voltage. When the EN is low the device consumes as low as

typ. 300 nA from the IN pin.

The device is fully protected in case of output overload,

output short circuit condition and overheating, assuring a

very robust design.

It is recommended to connect a minimum of 1

mF Ceramic

X5R or X7R capacitor close to the IN pin of the device. This

capacitor will provide a low impedance path for unwanted

AC signals or noise modulated onto constant input voltage.

There is no requirement for the min./max. ESR of the

input capacitor but it is recommended to use ceramic

capacitors for their low ESR and ESL. A good input

capacitor will limit the influence of input trace inductance

and power source resistance during sudden load current

changes. Larger input capacitor may be necessary if fast and

large line/load transients are encountered in the application.

The NCP729 is designed to operate with a small 1.0

mF

ceramic capacitor on the output. To assure proper operation

it is recommended to use min. 1.0

mF capacitor with the

initial tolerance of

±10%, made of X7R or X5R dielectric

material types.

NCP729 is internally compensated so there is no

requirement for the minimum value of Equivalent Series

ESR should be less than 500 m

W.

Larger output capacitors could be used to improve the load

transient response or high frequency PSRR. This part is not

designed to work with tantalum or electrolytic capacitors on

the output due to their large ESR and ESL. The equivalent

series resistance of tantalum capacitors is also strongly

dependent on the temperature, increasing at low

temperatures. The tantalum capacitors are generally more

costly than ceramic capacitors.

The table below lists examples of suitable output

capacitors:

Part Number

Description

C0402C105K8PACTU

1 mF Ceramic ±10%,

10 V, 0402, X5R

C1005X5R1A105K

-||-

GRM155R61A105KE15D

-||-

0402ZD105KAT2A

-||-

MCCA000571

1 mF Ceramic ±10%,

50 V, 1206, X7R

ECJ−0EB0J475M

4.7 mF Ceramic ±20%,

6.3 V, 0402, X5R

No−load Operation

The regulator remains stable and regulates the output

voltage properly within the

±2% tolerance limits with no

external load applied to the output.

Enable Operation

The NCP729 uses the EN pin to enable, disable its output

and to deactivate, activate the active output discharge

function.

If the EN pin voltage is <0.4 V the device is guaranteed to

be disabled. The pass transistor is turned−off and the active

is pulled to GND through a 1 k

W resistor. In the disable state

If the EN pin voltage > 0.9 V the device is guaranteed to

be enabled. The output voltage is regulated at the nominal

value and the active discharge transistor is turned−off.

The EN pin has internal pull−down current source with

typ. value of 110 nA which assures that the device is

turned−off when the EN pin is not connected. A build in

2 mV of hysteresis in the EN prevents from periodic on/off

oscillations that can occur due to noise.

In the case where the EN function isn’t required the EN

pin should be tied directly to IN.

Undervoltage Lockout

The internal UVLO circuitry assures that the device

Reverse Current

The PMOS pass transistor has an inherent body diode

Due to this fact in cases where the extended reverse current

condition is anticipated the device may require additional

external protection.