California Micro Devices CMPWR280 Datasheet

CALIFORNIA MICRO DEVICES

CMPWR280

1.5A SmartORTM Dual Regulator with V

Features

 Automatic selection of V

 Drive control signal for external V

 Continuous 3.3V output supply

 Glitch-free output during supply transitions

 Built-in hysteresis for supply selection

regulates up to 1.5A output current

V

CC

V

regulates up to 375mA output current

SBY

 Foldback current limiting

 Thermal shutdown with hysteresis

 On-chip controller operates from VCC, V

Applications

 Peripheral Component Interface (PCI) Adapter Cards

 Network Interface Cards (NICs)

 Multiple Powered Systems

 Systems with Standby Capabilities

Product Description

The California Micro Devices SmartOR

protected Dual-Input low dropout CMOS regulator that also

provides the necessary control signal for driving an external

auxiliary Pchannel MOSFET switch. The SmartORTM device au-

tomatically selects one of three possible inputs on a priority

basis: V

(1.5A), V

CC

(375mA) or V

SBY

used to control an external switch.

CC

or V

SBY

switch

AUX

or V

SBY

TM

CMPWR280 is a fully

via the drive signal

AUX

OUT

Drive

AUX

Pin Diagram

Typical Application Circuit

VCC is given first priority. In the event of the VCC supply being

powered down, the device will automatically deselect the V

prior to regulator dropout and immediately select V

SBY

priority) as its power source.

If neither VCC nor V

are present the drive control output will

SBY

CC

(second

Simplified Electrical Schematic

turn-on an external P-channel MOSFET switch from an auxiliary

to V

3.3V supply V

AUX

OUT

.

All the necessary control circuitry needed to provide a smooth

and automatic transition between all three supplies has been

incorporated. This allows V

to be dynamically switched with-

CC

out loss of output voltage.

The CMPWR280 is internally protected against output

short-circuits, current overload and thermal overload.

TS

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When placing an order please specify desired shipping: Tubes or Tape & Reel.

NOITAMROFNIGNIREDROTRAPD

© 2000 Calirornia Micro Devices Corp. All rights reserved.

3/00

215 Topaz Street, Milpitas, California 95035 Tel: [phone] Fax: [phone] www.calmicro.com

CMPWR300 is a trademark of California Micro Devices Corp.

C0660200

1

CALIFORNIA MICRO DEVICES

CMPWR280

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Note 1: The maximum power dissipation of this device is internally limited by thermal shutdown circuitry. To achieve a power dissipation of 3.0

watts, a case-to-ambient thermal resistance of 25°C/W must be provided. This will typically require dedicated heatsinking ability of the

printed circuit board. For more details, please see the Typical Thermal Characteristics section.

Note 2: The hysteresis defines the maximum level of acceptable disturbance on V

Ω

Note 3: Ground pin current consists of controller current (0.2mA) and regulator current when selected

impedance be kept below 0.15

©2000 California Micro Devices Corp. All rights reserved.

2

215 Topaz Street, Milpitas, California 95035 Tel: [phone] Fax: [phone] www.calmicro.com

to ensure the switching disturbance remains below the hysteresis during select/deselect transitions.

during switching. It is recommended that the VCC source

CC

µA

µs

°C

3/00

CALIFORNIA MICRO DEVICES

Interface Signals

V

is the primary 5V power supply for the internal regulator.

CC

Whenever V

(1500mA) will be enabled and deliver a fixed 3.3V at V

When V

will be disabled.

Internal loading on this pin is typically 1.5mA when the

regulator is enabled, which reduces to 0.2mA whenever

the regulator is disabled. If V

voltage, the loading on VCC will reduce to only a few

V

OUT

microamperes.

During a VCC power up sequence, there will be an effective

step increase in V

The amplitude of this step increase will depend on the dc

load current and any current required for charging/

discharging the load capacitance. This line current transient

will cause a voltage disturbance at the V

to the effective power supply source impedance being

delivered to the V

To prevent chatter during Select and Deselect transitions, a

built-in hysteresis voltage of 400mV has been incorporated.

It is recommended that the power supply connected to the

V

input should have a source impedance of less than 0.15Ω

CC

to minimize the chatter during the enabling/disabling of

the regulator.

exceeds V

CC

falls below V

CC

line current when the regulator is enabled.

CC

CC

CCDES

input.

(4.5V), the internal regulator

CCSEL

(4.1V typically) the regulator

falls below either the V

CC

pin proportional

CC

SBY

OUT

or

CMPWR280

GND is the reference for all voltages. The current that flows

in the ground connection is very low (typically 2.0mA) and

.

has minimal variation over all load conditions

V

is the regulator output voltage connection used to power

OUT

the load. An output capacitor of ten microfarads is used to

provide the necessary phase compensation, thereby preventing

oscillation. This capacitor also helps to minimize the peak

output disturbance during power supply changeover.

When both VCC and V

provide the necessary quiescent current for the internal

reference circuits. This ensures excellent start-up characteristics

for the regulator.

Drive is an active LOW logic output intended to be used as

the control signal for driving an external P-channel MOSFET

switch whenever the regulator is disabled. This will allow the

voltage at V

to be powered from an auxiliary supply voltage

OUT

(3.3V).

The Drive pin is pulled HIGH to VCC whenever the regulator is

enabled, thus ensuring that the auxiliary supply remains isolated

during normal regulator operation.

fall below V

SBY

OUT

, V

will be used to

OUT

is the standby 5V supply power source, which is only

V

SBY

selected on when V

< V

CC

CCDES

. If V

is selected, the

SBY

regulator can deliver a maximum of 375mA load current.

Whenever V

exceeds both V

SBY

and V

CC

, it will be used to

OUT

provide all the internal bias currents and any necessary

regulator current.

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© 2000 Calirornia Micro Devices Corp. All rights reserved.

3/00

215 Topaz Street, Milpitas, California 95035 Tel: [phone] Fax: [phone] www.calmicro.com

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