LP3936 Datasheet, PDF (22/30 Pages) National Semiconductor (TI) – Lighting Management System for Six White LEDs and One RGB or FLASH LED

LP3936
SNVS259D – NOVEMBER 2003 – REVISED MAY 2013
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INDUCTOR, L
The high switching frequency enables the use of the small surface mount inductor. A 10 µH shielded inductor is
suggested. Values below 4.7 µH should not be used. The inductor should have a saturation current rating higher
than the peak current it will experience during circuit operation (1A). Less than 300 mΩ ESR is suggested for
high efficiency. Open core inductors cause flux linkage with circuit components and interfere with the normal
operation of the circuit. This should be avoided. For high efficiency, choose an inductor with a high frequency
core material such as ferrite to reduce the core losses. To minimize radiated noise, use a toroid, pot core or
shielded core inductor. The inductor should be connected to the OUT pin as close to the IC as possible.
Examples of suitable inductors are TDK types LLF4017T-100MR90C and VLF4012AT-100MR79 and Coilcraft
type DO3314T-103 (unshielded).
Symbol
C_VDD1
C_VDD2
C_OUT
C_IN
C_VDDIO
C_VDDA
RT
RDO
C_VREF
L_BOOST
D_OUT
RGB
R_R, R_G, R_B
LEDs
List of Recommended External Components
Symbol Explanation
Value
Unit
Type
V_DD1 bypass capacitor
1
V_DD2 bypass capacitor
1
Output capacitor from FB
10
to GND
µF
Ceramic, X7R
µF
Ceramic, X7R
µF
Ceramic, X7R/Y5V
Input capacitor from
10
Battery Voltage to GND
µF
Ceramic, X7R/Y5V
V_DDIO bypass capacitor
1
Internal LDO output
1
capacitor, between V_DDA
and GND
Oscillator Frequency Bias
82
Resistor
µF
Ceramic, X7R
µF
Ceramic, X7R
kΩ
1% ⁽¹⁾
DO output pull-up resistor
100
kΩ
Reference Voltage
100
Capacitor, between V_REF
and GND
nF
Ceramic, X7R
Boost converter inductor
10
Rectifying Diode, V_F @
0.3
Maxload
µH
Shielded, Low ESR,
I_SAT1A
V
Schottky Diode
RGB LED
Current Limit Resistors
White LEDs
User Defined
See the AN-1293 Application Report (SNVA071) for resistor size calculation.
(1) Resistor RT tolerance change will change the timing accuracy of the RGB block. Also the boost converter switching frequency will be
affected.
22
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