LM3687 Datasheet, PDF (16/35 Pages) National Semiconductor (TI) – Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode

LM3687
SNVS473A – DECEMBER 2007 – REVISED JULY 2008
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Typical Performance Characteristics (continued)
Unless otherwise specified, typical application (post regulation), V_BATT = 3.6V, T_A = 25°C, enable pins tied to V_BATT, V_{OUT_DCDC}
= 1.8V, V_{OUT_LIN} = 1.2V
V_{OUT_DCDC}
vs.
V_{OUT_LIN}
vs.
Temperature
Temperature
1.820
1.818
1.816
PFM Mode
1.814
1.812
1.810
1.808
1.806
PWM Mode
1.804
1.802
1.800
1.798
1.796
-40 -20 0 20
I_{OUT_DCDC} = 10 mA
I_{OUT_DCDC} = 150 mA
I_{OUT_DCDC} = 750 mA
40 60 80 100 120 140
TEMPERATURE (°C)
1.202
1.201
I_{OUT_LDO} = 1 mA
1.200
1.199
1.198
1.197
1.196
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Efficiency DC-DC
vs.
Output Current
LDO disabled
Startup into no load
100
90
V_BATT = 2.8V
80
V_BATT = 4.2V
70
60
50
40
30
20
10
0.01
0.1
1
10 100 1000
OUTPUT CURRENT DC-DC (mA)
V_{OUT_LIN}
I_L
V_{OUT_DCDC}
V_{EN_LIN/DCDC}
40 és/DIV
1V/DIV
200 mA/DIV
1V/DIV
1V/DIV
V_{OUT_LIN}
I_L
V_{OUT_DCDC}
V_{EN_LIN/DCDC}
Startup into load
I_{OUT_LN} = 50 mA
1V/DIV
500 mA/DIV
1V/DIV
I_{OUT_DCDC} = 700 mA
1V/DIV
100 és/DIV
V_BATT Line Transient Response (PWM Mode)
V_BATT
500 mV/DIV
3.6V
3.0V
V_{OUT_LIN}
I_{OUT_LIN} = 300 mA
5 mV/DIV
AC Coupled
V_{OUT_DCDC}
= V_{IN_LIN}
I_{OUT_DCDC} = 400 mA
50 mV/DIV
AC Coupled
100 és/DIV
16
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