ISL80101A 查看數據表（PDF） - Intersil
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ISL80101A Datasheet PDF : 11 Pages
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ISL80121-5
Typical Operating Performance Unless otherwise noted: VIN = 5.4V, VOUT = 5.0V, CIN = COUT = 10µF,
TJ = +25°C, IL = 0A. (Continued)
1.0
RSET = 20kΩ
0.9
0.8
0.7
RSET = OPEN
0.6
0.5
VOUT (50mV/DIV)
0.4
0.3
0.2
0.1
0
-40
10
60
110
TEMPERATURE (°C)
FIGURE 7. CURRENT LIMIT vs TEMPERATURE
IOUT = 500mA
IOUT = 10mA
TIME (50µs/DIV)
FIGURE 8. LOAD TRANSIENT RESPONSE
100mA LOAD
40
1A LOAD
30
20
10
0
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FIGURE 9. PSRR vs LOAD
Functional Description
Input Voltage Requirements
The ISL80121-5 is optimized for 5V output, and can operate from
input voltages of 2.2V to 6V. Due to the nature of an LDO, VIN
must be some margin higher than VOUT plus dropout at the
maximum rated current of the application if active filtering
(PSRR) is expected from VIN to VOUT. The generous dropout
specification of this family of LDOs allows applications to design
for a level of efficiency that can accommodate profiles smaller
than the TO220/263.
Programmable Current Limit
The ISL80121-5 protects against overcurrent due to short-circuit
and overload conditions applied to the output. When this
happens, the LDO performs as a constant current source. If the
short-circuit or overload condition is removed, the output returns
to normal voltage regulation operation.
60 LOAD = 100mA
50
40
COUT = 100µF
COUT = 47µF
30
20
COUT = 22µF
10
COUT = 10µF
0
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FIGURE 10. PSRR vs COUT
The current limit is set at 0.75A by default when the ISET pin is
left floating.
This limit can be increased by tying a resistor RSET from the ISET pin to
ground. The current limit is determined by RSET as shown in
Equation 1:
ILIMIT = 0.75 + -R----S---E--2-T--.-(-9--k---Ω------)
(EQ. 1)
Figure 11 shows the relationship between RSET and the current
limit when the RSET is tied from ISET pin to GND. Do not short this
pin to ground. Increasing the current limit past 1.75A may cause
damage to the part and is highly discouraged.
7
FN7713.4
September 29, 2011
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