CMPWR101ST 查看數據表（PDF） - California Micro Devices Corp
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CMPWR101ST Datasheet PDF : 6 Pages
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CALIFORNIA MICRO DEVICES
CMPWR101
Interface Signals
VCC is the power source for the internal regulator and is
monitored continuously by an internal controller circuit.
Whenever VCC exceeds VCCSEL (4.25V typically), the
internal regulator will be enabled and deliver a fixed
3.3V at VOUT. 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 VCC falls below the voltage on
the VAUX pin, the VCC loading will further reduce to only a
few microamperes.
During a VCC power-up or power-down sequence, there
will be an effective step increase in VCC line current
when the regulator is enabled/disabled. This line current
transient will cause a voltage disturbance at the VCC pin.
The magnitude of the disturbance will be directly
proportional to the effective power supply source
impedance being delivered to the V input.
CC
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 VCC input should have a source
resistance of less than 0.25Ω to minimize the event of
chatter during the enabling/disabling of the regulator.
If the VCC 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.
VAUX is the auxiliary power source. When selected,
(VCC < VCCDES), the auxiliary supply is directly connected
to VOUT, 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 VCC falls below the
voltage on VAUX.
When V = 0V, the V voltage is inhibited which
AUX
CCDES
prevents the regulator from being disabled.
VOUT 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 VCC 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
Pin
Symbol
Description
1
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.
8
DRIVE Output Control Signal which is taken LOW whenever VCC is unavailable
4
GND Negative reference for all voltages
5
NC
Unconnected pin which is electrically isolated from internal circuitry.
VCC
+
VDESELECT
4.1V
VAUX
3.3V
GND
–
0.2Ω
VREF
3.3V
ENABLE
+
–
DRIVE
VOUT
3.3V
250mA
Simplified Electrical Schematic
© 2001 California Micro Devices Corp. All rights reserved. SmartOR™ is a trademark of California Micro Devices Corporation.
215 Topaz Street, Milpitas, California 95035 Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
3/6/2001
3
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