CMPWR101ST datasheet(3/6 Pages) CALMIRCO

3 / 6 page

CALIFORNIA MICRO DEVICES

3/6/2001

215 Topaz Street, Milpitas, California 95035

Tel: (408) 263-3214

Fax: (408) 263-7846

www.calmicro.com

CMPWR101

Interface Signals

CC is the power source for the internal regulator and is

monitored continuously by an internal controller circuit.

Whenever V

CC exceeds VCCSEL (4.25V typically), the

internal regulator will be enabled and deliver a fixed

3.3V at V

OUT. When VCC falls below VCCDES (4.10V typi-

cally), the regulator will be disabled.

Internal loading on this pin is typically 0.6mA when the

regulator is enabled, which reduces to 0.1mA whenever

the regulator is disabled. If V

CC falls below the voltage on

the V

AUX pin, the VCC loading will further reduce to only a

few microamperes.

During a V

CC power-up or power-down sequence, there

will be an effective step increase in V

CC line current

when the regulator is enabled/disabled. This line current

transient will cause a voltage disturbance at the V

CC pin.

The magnitude of the disturbance will be directly

proportional to the effective power supply source

impedance being delivered to the V

CC input.

A built-in hysteresis voltage of 150mV has been

incorporated to minimize any chatter during supply

changeover. It is recommended that the power supply

connected to the V

CC input should have a source

resistance of less than 0.25

Ω to minimize the event of

chatter during the enabling/disabling of the regulator.

If the V

CC pin is within a few inches of the main input

filter, a capacitor may not be necessary. Otherwise an

input filter capacitor in the range of 1µF to 10µF will help

to lower the effective source impedance.

AUX is the auxiliary power source. When selected,

CC < VCCDES), the auxiliary supply is directly connected

to V

OUT, via the low impedance (0.3Ω typically) fully

integrated switch.

The internal loading on this pin is typically less than

10µA and will increase to 100µA if V

CC falls below the

voltage on V

AUX.

When V

AUX = 0V, the VCCDES voltage is inhibited which

prevents the regulator from being disabled.

OUT is the regulator output voltage connection used to

power the load. An output capacitor of 4.7µF is used to

provide the necessary phase compensation, thereby

preventing oscillation. The capacitor also helps to

minimize the peak output disturbance during power

supply changeover.

DRIVE is a CMOS output logic signal (Active Low)

referenced to the V

CC supply. This output is taken low

whenever the internal regulator is not enabled. This

output is intended only as a control signal for external

circuitry.

GND is the negative reference for all voltages. The

current that flows in the ground connection is very low

(typically 0.6mA) and has minimal variation over all load

conditions.

NC is an unconnected pin which is electrically isolated

from the internal circuitry.

PIN FUNCTIONS

Symbol

Description

VCC

Positive (5V) supply input for regulator. (VCC > VCCSEL)

2, 3

VAUX

Auxiliary supply input is connected directly to the output via a low impedance

when the regulator is disabled.

6, 7

VOUT

Continuous output voltage (3.3V) is derived from either the internal regulator or low impedance

switch connected to the auxiliary supply input.

DRIVE

Output Control Signal which is taken LOW whenever VCC is unavailable

GND

Negative reference for all voltages

Unconnected pin which is electrically isolated from internal circuitry.

Simplified Electrical Schematic

VOUT

3.3V

250mA

–

VCC

–

VDESELECT

4.1V

VAUX

3.3V

GND

0.2

Ω

DRIVE

ENABLE

VREF

3.3V

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