LTC3642 Datasheet, PDF (5/20 Pages) Linear Technology – High Effi ciency, High Voltage 50mA Synchronous Step-Down Converter

TYPICAL PERFORMANCE CHARACTERISTICS
LTC3642
Switch On-Resistance vs
Input Voltage
4.5
4.0
3.5
3.0
TOP
2.5
2.0
BOTTOM
1.5
1.0
0.5
0
0
10
20
30
40
50
V_IN VOLTAGE (V)
3642 G10
Efficiency vs Input Voltage
95
FIGURE 10 CIRCUIT
I_SET OPEN
90
I_LOAD = 50mA
85
I_LOAD = 10mA
80
I_LOAD = 1mA
75
Switch On-Resistance vs
Temperature
5
V_IN = 10V
4
TOP
3
BOTTOM
2
1
0
–40 –10 20 50 80
TEMPERATURE (°C)
110
3642 G11
Run Comparator Thresholds vs
Temperature
1.30
1.25
RISING
1.20
1.15
FALLING
1.10
Switch Leakage Current vs
Temperature
0.6
V_IN = 45V
0.5
0.4
SW = 0V
0.3
0.2
SW = 45V
0.1
0
–40 –10 20 50 80
TEMPERATURE (°C)
110
3642 G12
Internal Soft-Start Time vs
Temperature
1.20
1.15
1.10
1.05
1.00
70
1.05
0.95
65
10 15 20 25 30 35 40 45
INPUT VOLTAGE (V)
3642 G13
1.00
–40
–10 20 50 80
TEMPERATURE (°C)
Soft-Start Waveforms
Operating Waveforms
OUTPUT
VOLTAGE
1V/DIV
INDUCTOR
CURRENT
50mA/DIV
OUTPUT
VOLTAGE
50mV/DIV
SWITCH
VOLTAGE
5V/DIV
INDUCTOR
CURRENT
50mA/DIV
V_IN = 10V
500μs/DIV
C_SS = 0.047μF
I_SET OPEN
FIGURE 10 CIRCUIT
4632 G16
V_IN = 10V
10μs/DIV
I_SET OPEN
FIGURE 10 CIRCUIT
110
3642 G14
4632 G17
0.90
–40
–10 20 50 80
TEMPERATURE (°C)
110
3642 G15
Load Step Transient Response
OUTPUT
VOLTAGE
25mV/DIV
LOAD
CURRENT
25mA/DIV
V_IN = 10V
1ms/DIV
I_SET OPEN
FIGURE 10 CIRCUIT
4632 G18
3642f
5