CALIFORNIA MICRO DEVICES
Typical Transient Characteristics
The transient characterization test setup is shown in
Figure 6. It was the setup used for the transient tests
unless specified otherwise.
A maximum rated load current of 6.6Ω (500mA @ 3.3V)
was used during characterization along with a nominal
V
CC
supply voltage of 5V DC, unless specified otherwise.
The load transient characterization was done by switch-
ing between 6.6 and 660Ω load resistors. This switched
the load between 500 and 5mA respectively.
For the V
CC
power-up and power-down characterizations
V
CC
supply was ramped between 0 and 5V. Both the rise
and fall times for the V
CC
power-up/down pulses were
controlled to be 15ms.
CMPWR160
In the line transient characterizations the V
CC
supply
voltage was controlled to step between 4.5 to 5.5V.
For the
POR
response characterization V
CC
and
SD
were
tied to ground and the V
OUT
voltage was directly driven
between 2.7 and 3.1V. This was done by connecting a
function generator directly to the output of the device.
These voltage values were picked because it drove V
OUT
directly across the typical
POR
threshold voltage of 2.9V.
V
CC
was tied to ground to show that the
POR
circuitry will
operate even when the V
CC
supply voltage is not present.
The oscilloscope traces show the full bandwidth re-
sponse at the
SD
,
POR
, V
CC
and V
OUT
pins depending on
the characterization.
CMPWR160
V
CC
V
CC
+ C1
10µF
C2
0.1µF
SD
POR
V
OUT
GND
POR
V
OUT
+ C3
0.1µF
GND
C4
10µF
(500mA)
6.6Ω
GND
Figure 6. Transient Characterization Test Setup
V
CC
power-up Cold Start
Figure 7 shows the output response during an initial V
CC
power up with
SD
tied to V
CC
. When V
CC
reaches a
particular threshold, the regulator turns on. The un-
charged output capacitor causes maximum inrush
current to flow. At this point the device sees the output
as a short circuit and the device enters a protective
current limiting mode. The output capacitor quickly
charges and V
OUT
rises. Once this voltage rises to just
below V
CC
the inrush current stops flowing and the output
rises with the input. V
OUT
continues to rise with the input
until it reaches 3.3V.
Tek Run 25.0kS/s Sample
VCC
VOUT
(500mA Load)
1.00V
Ch2 1.00V M 2.00ms Ch2
280mV
Figure 7. V
CC
Power-up Cold Start
©2000 California Micro Devices Corp. All rights reserved. SmartOR™ is a trademark of California Micro Devices Corporation.
6
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
12/5/2000
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
