LTC3879_15 Datasheet, PDF (6/28 Pages) Linear Technology – Fast, Wide Operating Range No RSENSE Step-Down Controller

LTC3879
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Input Voltage
100
95
90
15A CCM
85
80
1A DCM
75
70
1A CCM
65
60
V_IN = 15V
V_OUT = 1.2V
55 ^{SW FREQ = 400kHz}
FIGURE 10 CIRCUIT
50
4 8 12 16 20 24 28
V_IN (V)
3879 G26
Current Sense Voltage
vs I_TH Voltage
300
250
200
150
100
50
0
–50
–100
–150
0
V_RNG = 0.2V
V_RNG = 0.5V
V_RNG = 1.0V
V_RNG = 1.5V
V_RNG = 2.0V
0.5
1
1.5
2
2.5
I_TH VOLTAGE (V)
3879 G12
Maximum V_DS Current Sense
Threshold vs V_RNG Voltage
300
250
200
150
100
50
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
V_RNG VOLTAGE (V)
3879 G15
Frequency vs Input Voltage
420
410
400
390
380
370
360
350
340
330
320
310
300
4
15A
0A
V_IN = 15V
V_OUT = 1.2V
FIGURE 10 CIRCUIT
8 12 16 20 24 28
V_IN (V)
3879 G10
On-Time vs I_ON Current
10000
FIGURE 10 CIRCUIT
1000
100
10
1
10
I_ON CURRENT (A)
100
3879 G13
Load Regulation FCM
0
–0.02
–0.04
V_IN = 15V
V_OUT = 1.2V
FIGURE 10 CIRCUIT
–0.06
–0.08
–0.10
–0.12
–0.14
–0.16
0
5
10
LOAD CURRENT (A)
15
3879 G16
Frequency vs Load Current
410
CONTINUOUS MODE
370
330
DISCONTINUOUS MODE
290
250
210
170
130
90
V_IN = 15V
50
V_OUT = 1.2V
FIGURE 10 CIRCUIT
10
0 2 4 6 8 10 12 14
I_LOAD (A)
3879 G11
Current Limit Foldback
140
V_RNG = 1V
FIGURE 10 CIRCUIT
120
100
80
60
40
20
0
0 0.1 0.2 0.3 0.4 0.5 0.6
V_FB (V)
3879 G14
I_TH Voltage vs Load Current
2.5
2.3
2.1
1.9
1.7
1.5
1.3
1.1
V_IN = 15V
V_OUT = 1.2V
0.9
FIGURE 10 CIRCUIT
0.7
CONTINUOUS MODE
DISCONTINUOUS MODE
0.5
0
5
10
15
20
25
LOAD CURRENT (A)
3879 G17
3879f
6