FN6867 Rev 2.00

Page 8 of 10

January 14, 2010

ISL9021

Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted

in the quality certifications found at www.intersil.com/en/support/qualandreliability.html

Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such

modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are

current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its

subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Intersil or its subsidiaries.

For information regarding Intersil Corporation and its products, see www.intersil.com

For additional products, see www.intersil.com/en/products.html

© Copyright Intersil Americas LLC 2009-2010. All Rights Reserved.

All trademarks and registered trademarks are the property of their respective owners.

Functional Description

The ISL9021 is a high performance low-dropout regulator

(LDO) with 250mA sourcing capability. The extra low ground

current makes this part a good choice for handheld product

applications. The device also incorporates overcurrent, thermal

shutdown, reverse current protections, and soft-start features.

Thermal shutdown protects the device against overheating.

Soft-start limits the start-up input current surges. In some

applications, the output voltage may be externally pulled higher

than input, or the input voltage could be connected to ground,

or connected to some voltage lower than the output side. The

ISL9021 features reverse current protection; that can block the

reverse current from output to input.

Enable Control

The ISL9021 has an enable pin. When EN is low, the IC is in

shutdown mode. In this condition, all on-chip circuits are off,

and the device draws minimum current, typically less than

0.1µA(typ). Driving this pin high will turn on the device.

LDO Protections

The ISL9021 offers several protection functions, making it ideal

for use in battery-powered applications.The ISL9021 provides

short-circuit protection by limiting the output current at current limit

of 260mA(min). If the short circuit lasts long enough, the die

temperature increases, and the over-temperature protection

circuit will shut down the output. When the die temperature

reaches about +145°C, thermal protection starts to work with

output being loaded with at least 50mA. Once the die temperature

drops to about +110°C, the LDO will resume operation beginning

with a soft-start.

The ISL9021’s reverse current protection is intended to block

reverse conduction if output voltage is higher than input

voltage.

Input and Output Capacitors

The ISL9021 provides a linear regulator that has low quiescent

current, fast transient response, and overall stable operation

across the recommended operating conditions. A ceramic

capacitor (X5R or X7R) with a capacitance of 1µF to 4.7µF with

an ESR up to 400m

 is suitable for the ISL9021 to maintain its

output stability. The ground connection of the output capacitor

should be routed directly to the GND pin of the device, and

also placed close to the IC. Similarly for the input capacitor,

usually a 1µF ceramic capacitor (X5R or 7R) is suitable for

most cases, but if a large, fast rising load transient condition is

expected, a higher value input capacitor may be necessary to

achieve satisfactory performance.

Board Layout Recommendations

A good PCB layout is an important step to achieve good

performance. It is recommended to design the board with

separate ground planes for input and output, and connect both

ground planes at the GND pin of the IC. Consideration should

be taken when placing the components and routing the trace to

minimize the ground impedance, and keep the parasitic

inductance low. Usually the input/output capacitors should be

placed as close to the IC as possible with a good ground

connection.