CMPWR101
http://onsemi.com
2
TYPICAL APPLICATION CIRCUIT
+
V
CC
CMPWR101
SIMPLIFIED ELECTRICAL SCHEMATIC
GND
V
AUX
DRIVE
V
OUT
V
OUT
C
OUT
4 mF
GND
V
OUT
GND
+
C
IN
1 mF
DRIVE
3.3 V/250 mA
3.3 V
5 V
V
AUX
V
CC
-
+
-
+
DRIVE
V
AUX
V
CC
ENABLE
0.2 W
V
DESELECT
4.1 V
V
REF
3.3 V
PACKAGE / PINOUT DIAGRAM
Top View
8−Pin SOIC
V
CC
1
2
3
4
DRIVE
V
OUT
N/C
8
7
6
5
V
AUX
V
AUX
GND
V
OUT
Table 1. PIN DESCRIPTIONS
Pin(s) Name Description
1 V
CC
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
(4.25 V typically), the internal regulator will be enabled and deliver
a fixed 3.3 V at V
OUT
.
When V
CC
falls below V
CCDES
(4.10 V typically), the regulator will be disabled. Internal loading on this pin is
typically 0.6 mA when the regulator is enabled, which reduces to 0.1 mA 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 150 mV 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 W 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 1 mF to 10 mF will help to lower the effective source impedance.
2−3 V
AUX
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 (0.3 W typically) fully integrated switch.
The internal loading on this pin is typically less than 10 mA and will increase to 100 mA if V
CC
falls below the
voltage on V
AUX
.
When V
AUX
= 0 V, the V
CCDES
voltage is inhibited which prevents the regulator from being disabled.
4 GND GND is the negative reference for all voltages. The current that flows in the ground connection is very low
(typically 0.6 mA) and has minimal variation over all load conditions.
5
NC
NC is an unconnected pin which is electrically isolated from the internal circuitry.
6−7 V
OUT
V
OUT
is the regulator output voltage connection used to power the load. An output capacitor of 4.7 mF 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.
8 DRIVE 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.
