LM3557 Datasheet, PDF (4/19 Pages) National Semiconductor (TI) – Step-Up Converter for White LED Applications

LM3557
SNVS338B – NOVEMBER 2004 – REVISED FEBRUARY 2013
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Electrical Characteristics ^{(1) (2)} (continued)
Limits in standard typeface are for T_J = 25°C. Limits in bold typeface apply over the full operating junction temperature range
(−40°C ≤ T_J ≤ +125°C). Unless otherwise specified: V_IN = 3.6V.
Parameter
Test Conditions
Min
Typ
Max
Units
I_LSw1
I_LSw2
I_LOVP
Sw1 Pin Leakage Current ⁽⁵⁾
Sw2 Pin Leakage Current ⁽⁵⁾
Ovp Pin Leakage Current ⁽⁵⁾
V_Sw1 = 3.6V, Not Switching
V_Sw2 = 3.6V, Not Switching
V_Ovp = 3.6V, Not Switching
0.002
2
µA
0.001
1
µA
2
nA
R_Sw2
Sw2 Pin Switch Resistance
I_Sw2 = 50 mA
8
10
Ω
TC(R_Sw2)
R_Sw2 Temperature Coefficient
0.5
%/C
Vin 2
BLOCK DIAGRAM
5 Ovp
OVP Diodes
Fb
6
NC
3
ERROR
AMPLIFIER
-
+
Fb
Reference
VREF
Sw2
+
-
7
4
N2
En
OVP
Schmitt
Trigger
Thermal Shutdown
PWM
Control and FET
Driver Logic
UVP COMPARATOR
+
-
UVP
Reference
1.2 MHz
Oscillator
+
CURRENT SENSE
-
AMPLIFIER
Sw1 1
N1
R
Figure 3.
Gnd 8
4
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