4
LTC3736
3736fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency and Power Loss
vs Load Current
V
OUT
AC-COUPLED
100mV/DIV
V
IN
= 3.3V
V
OUT
= 1.8V
I
LOAD
= 300mA TO 3A
SYNC/FCB = V
IN
FIGURE 17 CIRCUIT
100
µ
s/DIV
3736 G02
I
L
2A/DIV
V
OUT
AC-COUPLED
100mV/DIV
V
IN
= 3.3V
V
OUT
= 1.8V
I
LOAD
= 300mA TO 3A
SYNC/FCB = 0V
FIGURE 17 CIRCUIT
100
µ
s/DIV
3736 G03
I
L
2A/DIV
Load Step (Burst Mode Operation)
Load Step
(Forced Continuous Mode)
Load Step (Pulse Skipping Mode)
V
OUT
AC-COUPLED
100mV/DIV
V
IN
= 3.3V
V
OUT
= 1.8V
I
LOAD
= 300mA TO 3A
SYNC/FCB = 550kHz EXTERNAL CLOCK
FIGURE 17 CIRCUIT
100
µ
s/DIV
3736 G04
I
L
2A/DIV
Burst Mode
OPERATION
SYNC/FCB = V
IN
FORCED
CONTINUOUS
MODE
SYNC/FCB = 0V
V
IN
= 3.3V
V
OUT
= 1.8V
I
LOAD
= 200mA
FIGURE 17 CIRCUIT
4
µ
s/DIV
3736 G05
PULSE
SKIPPING MODE
SYNC/FCB = 550kHz
I
L
1A/DIV
V
IN
= 5V
R
LOAD1
= R
LOAD2
= 1
Ω
FIGURE 15 CIRCUIT
200
µ
s/DIV
3736 G06
500mV/
DIV
V
OUT1
2.5V
V
OUT2
1.8V
Inductor Current at Light Load
Tracking Start-Up with Internal
Soft-Start (C
SS
= 0
µ
F)
V
IN
= 5V
R
LOAD1
= R
LOAD2
= 1
Ω
FIGURE 15 CIRCUIT
40ms/DIV
3736 G07
500mV/
DIV
V
OUT1
2.5V
V
OUT2
1.8V
INPUT VOLTAGE (V)
2
–5
NORMALIZED FREQUENCY SHIFT (%)
–4
–2
–1
0
5
2
4
6
7
3736 G08
–3
3
4
1
3
5
8
9
10
Oscillator Frequency
vs Input Voltage
Tracking Start-Up with External
Soft-Start (C
SS
= 0.15
µ
F)
T
A
= 25
°
C unless otherwise noted.
LOAD CURRENT (mA)
65
EFFICIENCY (%)
95
100
60
55
90
75
85
80
70
1
100
1000
10000
3736 G01
50
10
FIGURE 15 CIRCUIT
POWER LOSS (W)
10
1
0.1
0.01
0.001
V
IN
= 5V
SYNC/FCB = V
IN
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
V
OUT
= 1.2V
