Datasheet

LTC3554/LTC3554-1/
LTC3554-2/LTC3554-3
10
3554123fd
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C, unless otherwise specified.
Step-Down Switching Regulator
Start-Up Waveform
V
OUT2
= 1.2V
I
OUT2
= 50mA
R
OUT1
= 22Ω
STBY = L
V
OUT2
50mV/DIV
(AC)
V
OUT1
1V/DIV
I
L1
100mA/DIV
0V
PWR_ON1
0mA
3554 G28
100µs/DIV
Step-Down Switching
Regulator Output Transient (STBY
High to Low)
Step-Down Switching
Regulator Output Transient
(FSEL Low to High)
V
OUT1
= 3.3V
I
OUT1
= 100mA
V
OUT2
= 1.2V
I
OUT2
= 50mA
STBY = L
V
OUT2
20mV/DIV
(AC)
V
OUT1
50mV/DIV
(AC)
FSEL
3554 G29
50µs/DIV
V
OUT1
= 3.3V
I
OUT1
= 5mA
V
OUT2
= 1.2V
I
OUT2
= 5mA
V
OUT2
20mV/DIV
(AC)
V
OUT1
20mV/DIV
(AC)
STBY
3554 G30
50µs/DIV
Step-Down Switching Regulator
Dropout Voltage in Standby Mode
vs Load Current
LOAD CURRENT (mA)
0 2 6 14121084
0
DROPOUT VOLTAGE (mV)
20
40
100
200
160
180
140
120
80
60
3554 G23
V
BVIN
= 2.9V
V
FBx
= 780mV
STBY = H
–45°C
25°C
90°C
Step-Down Switching
Regulator Switch Impedance
vs Temperature
TEMPERATURE (°C)
–75 –50 –25 25 50 75 100 1501250
0
SWITCH IMPEDANCE (Ω)
0.4
0.6
1.6
0.8
1.0
1.2
1.4
3554 G20
0.2
PMOS
NMOS
BV
IN
= 3.2V
STBY = L
Step-Down Switching
Regulator Feedback Voltage
vs Output Current
OUTPUT CURRENT (mA)
FEEDBACK VOLTAGE (V)
3554 G21
0.1 1 100 100010
0.780
0.790
0.795
0.820
0.800
0.805
0.810
0.815
0.785
3.8V
5V
STBY = L