CALIFORNIA MICRO DEVICES
Interface Signals
V
CC
is the power source for the internal regulator and is
monitored continuously by an internal controller circuit.
Whenever V
CC
exceeds V
CCSEL
(4.25V typically), the
internal regulator will be enabled and deliver a fixed
3.3V at V
OUT
. When V
CC
falls below V
CCDES
(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 V
CC
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 0.25Ω 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.
CMPWR101
V
AUX
is the auxiliary power source. When selected,
(V
CC
< V
CCDES
), 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 V
CCDES
voltage is inhibited which
prevents the regulator from being disabled.
V
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
Pin
1
2, 3
6, 7
8
4
5
Symbol
V
CC
V
AUX
V
OUT
DRIVE
GND
NC
Description
Positive (5V) supply input for regulator. (V
CC
> V
CCSEL
)
Auxiliary supply input is connected directly to the output via a low impedance
when the regulator is disabled.
Continuous output voltage (3.3V) is derived from either the internal regulator or low impedance
switch connected to the auxiliary supply input.
Output Control Signal which is taken LOW whenever V
CC
is unavailable
Negative reference for all voltages
Unconnected pin which is electrically isolated from internal circuitry.
V
CC
+
–
DRIVE
V
DESELECT
4.1V
0.2Ω
V
AUX
3.3V
GND
V
REF
3.3V
+
–
ENABLE
V
OUT
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
3/6/2001
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
3
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
