LM3687 Datasheet, PDF (17/35 Pages) National Semiconductor (TI) – Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode

LM3687
www.ti.com
SNVS473A – DECEMBER 2007 – REVISED JULY 2008
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
Load Transient Response DC-DC
V_{IN_LIN} Line Transient Response
(PWM Mode: 100mA to 750mA)
V_{IN_LIN}
500 mV/DIV
2.6V
2.0V
V_{OUT_LIN}
I_{OUT_LIN} = 350 mA
1 mV/DIV
AC Coupled
100 és/DIV
Load Transient Response DC-DC
(PFM Mode: 1mA to 50mA)
no load
V_{OUT_LIN}
5 mV/DIV
AC Coupled
V_{OUT_DCDC}
20 mV/DIV
AC Coupled
I_{OUT_DCDC}
500 mA/DIV
40 Ps/DIV
750 mA
100 mA
Load Transient Response Linear Regulator
0mA to 350mA
no load
V_{OUT_LIN}
V_SW
V_{OUT_DCDC}
5 mV/DIV
AC Coupled
2V/DIV
10 mV/DIV
AC Coupled
V_{OUT_LIN}
350 mA
I_{OUT_LIN}
0 mA
10 mV/DIV
AC Coupled
200 mA/DIV
I_{OUT_DCDC}
50 mA/DIV
40 Ps/DIV
50 mA
1 mA
Mode Change by Load Transients
(PFM to PWM)
V_{OUT_DCDC}
PWM
PFM
20 mV/DIV
AC Coupled
400 és/DIV
Mode Change by Load Transients
(PWM to PFM)
V_SW
2V/DIV
PFM
V_{OUT_DCDC}
PWM
50 mV/DIV
AC Coupled
500 mA
I_{OUT_DCDC}
V_{OUT_LIN}
V_{OUT_DCDC}
200 mA/DIV
4 Ps/DIV
50 mA
Output Ripple PFM Mode
I_{OUT_LIN} = 20 mA
Both Outputs:
10 mV/DIV
AC Coupled
BW = 1 GHz
I_L
200 mA/DIV
V_SW
1.0 és/DIV
2V/DIV
V_SW
PWM
V_{OUT_DCDC}
2V/DIV
PFM
20 mV/DIV
AC Coupled
I_{OUT_DCDC}
V_SW
500 mA
200 mA/DIV
4 Ps/DIV
50 mA
Output Ripple PWM Mode
V_BATT = 4.2V
5V/DIV
V_BATT
V_{OUT_DCDC}
V_{OUT_LIN}
I_{OUT_LIN} = 350 mA
100 ns/DIV
100 mV/DIV
Outputs, V_BATT:
AC Coupled
BW = 1 GHz
Both Outputs:
10 mV/DIV
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