CMPWR150SAR 查看數據表（PDF） - California Micro Devices Corp
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CMPWR150SAR Datasheet PDF : 8 Pages
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CALIFORNIA MICRO DEVICES
Typical DC Characteristics (continued)
CMPWR150
VCC Supply Current of the device is shown across the entire VCC
range for both VAUX present (3.3V) and absent (0V) in Figure 4.
In the absence of VAUX, the supply current remains fixed at
approximately 0.15mA until VCC reaches the Select voltage
threshold of 4.35V. At this point the regulator is enabled
and a supply current of 1.0mA is conducted.
When VAUX is present, the VCC supply current is less than
10µA until VCC exceeds VAUX, at which point VCC then powers
the controller (0.15mA). When VCC reaches VSELECT, the
regulator is enabled.
During a selection or deselection transition, the DC load
current is switching from VAUX to VCC and vice versa. In
addition to the normal load current, there may also be an
in-rush current for charging/discharging the load capacitor.
The total current pulse being applied to either VAUX or VCC is
equal to the sum of the dc load and the corresponding in-
rush current. Transient currents in excess of 1.0 amps can
readily occur for brief intervals when either supply
commences to power the load.
The oscilloscope traces of VCC power-up/down show the
full bandwidth response at the VCC and VOUT pins under full
load (500mA) conditions.
See Application Note AP-211 for more information.
VCC Power-up Cold Start. Figure 5 shows the output
response during an initial VCC power-up with VAUX not
present. When VCC reaches the select threshold, the
regulator turns on. The uncharged output capacitor causes
maximum in-rush current to flow, resulting in a large
voltage disturbance at the VCC pin of about 230mV. The
built-in hysteresis of 250mV ensures the regulator remains
enabled throughout the transient.
Figure 4. VCC Supply Current (No Load).
Prior to VCC reaching an acceptable logic supply level (2V),
a disturbance on the Drive pin can be observed.
Typical Transient Characteristics
The transient characterization test set-up shown below
includes the effective source impedance of the VCC supply
(RS). This was measured to be approximately 0.2Ω. It is
recommended that this effective source impedance be no
greater than 0.25Ω to ensure precise switching is maintained
during VCC selection and deselection.
Both the rise and fall times during VCC power-up/down
sequencing were controlled at a 20 millisecond duration.
This is considered to represent worst case conditions for
most application circuits.
A maximum rated load current of 500mA was used during
characterization, unless specified otherwise.
Figure 5. VCC Power-up Cold Start.
CMPWR150
F
Transient Characteristics Test Set-up
© 1999 California Micro Devices Corp. All rights reserved.
9/99
215 Topaz Street, Milpitas, California 95035 Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com
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