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參數(shù)資料
| 型號： | UCC381-x |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | Low Dropout 1 Ampere Linear Regulator Family |
| 中文描述： | 低壓差一安培線性穩(wěn)壓器系列 |
| 文件頁數(shù)： | 5/10頁 |
| 文件大?。?/td> | 102K |
| 代理商： | UCC381-X |
5
UCC281-3/-5/-ADJ
UCC381-3/-5/-ADJ
Overview
The UCC381 family of low dropout linear (LDO) regula-
tors provide a regulated output voltage for applications
with up to 1A of load current. The regulator features a
low dropout voltage and short circuit protection, making
their use ideal for demanding high current applications
requiring fault tolerance.
Short Circuit Protection
The UCC381 provides unique short circuit protection
circuitry that reduces power dissipation during a fault.
When an overload situation is detected, the device en-
ters a pulsed mode of operation at 3% duty cycle re-
ducing the heat sink requirements during a fault. The
UCC381 has two current thresholds that determine its
behavior during a fault as shown in Fig. 1.
When the regulator current exceeds the
Overcurrent
Threshold
for a period longer than the T
ON
, the
UCC381 shuts off for a period (T
OFF
) which is 32 times
T
ON
. If the short circuit current exceeds the
Peak Cur-
rent Limit
, the regulator limits the current to peak cur-
rent limit during the T
ON
period. The peak current limit
is nominally 1 Amp greater than the overcurrent thresh-
old. The regulator will continue in pulsed mode until the
fault is cleared as illustrated in Fig. 1.
A capacitive load on the regulator’s output will appear as a
short circuit during start-up. If the capacitance is too large,
the output voltage will not come into regulation during the
initial T
ON
period and the UCC381 will enter pulsed mode
operation. The peak current limit, T
ON
period, and load
characteristics determine the maximum value of output ca-
pacitor that can be charged. For a constant current load
the maximum output capacitance is given as follows:
(
)
(
)
C
I
I
T
V
Farads
OUT
CL
LOAD
ON
OUT
max
=
(1)
For worst case calculations the minimum values of on time
(T
ON
) and peak current limit (I
CL
) should be used. The ad-
justable version allows the T
ON
time to be adjusted with a
capacitor on the CT pin:
)
(
)
ON adj
(
)
T
C
Farads
μ
μ
sec
,
=
660 000
(2)
For a resistive load (R
LOAD
) the maximum output capacitor
can be estimated from:
C
OUT
(
)
T
R
n
V
I
R
ON
LOAD
OUT
CL
LOAD
max
=
l
1
1
Farads
(3)
APPLICATION INFORMATION
32T
ON
T
ON
T
ON
T
ON
32T
ON
32T
ON
V
(nom)
OUTPUT
VOLTAGE
I
O
(nom)
OUTPUT
CURRENT
R
OL
I
CL
PEAK CURRENT
LIMIT
OVERCURRENT
THRESHOLD
OVERLOAD
Figure 1. UCC381 short circuit timing.
UDG-98150
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