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LM3687 Datasheet, PDF (7/35 Pages) National Semiconductor (TI) – Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode
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LM3687
www.ti.com
SNVS473A – DECEMBER 2007 – REVISED JULY 2008
Electrical Characteristics(1) (2) DC-DC Converter (3)
Typical values and limits appearing in standard typeface are for TA = 25°C. Limits appearing in boldface type apply over the
full operating temperature range: -30°C ≤ TJ ≤ +125°C. Unless otherwise noted, VIN_LIN = VOUT_LIN(NOM) + 0.3V, VBATT = 3.6V,
IOUT_LIN = 1mA, VEN_DCDC = VEN_LIN = VBATT, CVBATT = 4.7µF, CVOUT_DCDC = 10µF, CVOUT_LIN = 2.2µF, CVIN_LIN = 1.0µF, L = 2.2µH.
Symbol
Parameter
Conditions
Typical
Limit
Units
Min
Max
VFB_DCDC Feedback Voltage
Accuracy
PWM Mode
-2.5
+2.5
%
Line Regulation
VOUT_DCDC + 1.0V ≤ VBATT ≤ 5.5V, IOUT_DCDC =
150mA
0.06
%/V
RDSON(P)
Load Regulation
Pin-Pin Resistance for
PFET
100mA ≤ IOUT_DCDC ≤ 750mA
0.0005
280
%/mA
500
mΩ
RDSON(N)
ILIM_DCDC
Pin-Pin Resistance for
NFET
Switch Peak Current
Limit
Open loop (4)
200
400
mΩ
1172
994
1380
mA
FOSC
Internal Oscillator
Frequency
PWM Mode
1.8
1.3
2.3
MHz
(1) All voltages are with respect to the potential at the SGND pin.
(2) Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the
most likely norm. Unless otherwise specified, conditions for typ. specifications are: VBATT = 3.6V and TA = 25°C.
(3) The parameters in the electrical characteristic table are tested at VBATT = 3.6V unless otherwise specified. For performance over the
input voltage range refer to datasheet curves.
(4) Refer to datasheet curves for closed loop data and its variation with regards to supply voltage and temperature. Electrical Characteristic
table reflects open loop data (FB=0V and current drawn from SW pin ramped up until cycle by cycle current limit is activated). Closed
loop current limit is the peak inductor current measured in the application circuit by increasing output current until output voltage drops
by 10%.
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