LT1521/LT1521-3
LT1521-3.3/LT1521-5
W
U
TYPICAL PERFORMANCE CHARACTERISTICS
Load Regulation
Ripple Rejection
0
–5
100
I
= 150mA
LOAD
IN
∆I
= 1mA TO 300mA
90
80
70
60
50
40
30
20
10
0
LOAD
V
= 6V + 50mV
RIPPLE
RMS
–10
–15
–20
–25
–30
–35
–40
LT1521-5
LT1521-3
LT1521*
LT1521-3.3
C
= 33µF
OUT
SOLID TANTALUM
C
= 3.3µF
V
= V
ADJ
(NOMINAL + 1V)
OUT
OUT
SOLID TANTALUM
IN
*V
= V
OUT
–25
0
50
75 100 125
–50
25
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
TEMPERATURE (°C)
LT1521 • TPC31
LT1521 • TPC32
LT1521-5
Transient Response
LT1521-5
Transient Response
V
C
C
= 6V
V
C
C
= 6V
IN
IN
IN
IN
0.2
0.1
0.2
0.1
= 0.1µF
= 33µF
= 0.1µF
= 1.5µF
OUT
OUT
0
0
–0.1
–0.2
–0.1
–0.2
150
100
50
300
200
100
0
50 100 150 200 250 300 350 400 450 500
0
0.5 1.0 1.5
2.5 3.0 3.5 4.0 4.5 5.0
2.0
TIME (µs)
TIME (ms)
LT1521 • TPC33
LT1521 • TPC34
U
U
U
PIN FUNCTIONS
theoutputpinoftheregulator.Incriticalapplicationssmall
voltage drops caused by the resistance (RP) of PC traces
between the regulator and the load, which would normally
degrade regulation, may be eliminated by connecting the
sense pin to the output at the load as shown in Figure 1
(Kelvin Sense Connection). Note that the voltage drop
across the external PC traces will add to the dropout
voltage of the regulator. The sense pin bias current is 5µA
at the nominal regulated output voltage. This pin is inter-
nally clamped to –0.6V (one VBE).
OUT (Pin 1): The output pin supplies power to the load. A
minimum output capacitor of 1.5µF is required to prevent
oscillations, but larger values of output capacitor will be
necessary to deal with larger load transients. See the
Applications Information section for more on output
capacitance and reverse output characteristics.
SENSE (Pin 2): For fixed voltage versions of the LT1521
(LT1521-3, LT1521-3.3, LT1521-5), the sense pin is the
input to the error amplifier. Optimum regulation will be
obtained at the point where the sense pin is connected to
1521335fb
8
Linear [ Linear ]
