LP3931 Datasheet, PDF (15/17 Pages) National Semiconductor (TI) – Dual RGB LED Driver with High Current Boost DC-DC Converter

Recommended External Components (Continued)
List of External Components
Symbol
Symbol Explanation
Value
Unit
Recommended Type
C_VDD1
C_VDD2
C_OUT
C_IN
C_VDDIO
RT
V_DD1 Bypass Capacitor
V_DD2 Bypass Capacitor
Output Capacitor from FB to GND
Input Capacitor from Battery Voltage to GND
V_{DD_IO} Bypass Capacitor
Oscillator Frequency Bias Resistor
100
nF Ceramic, X7R
100
nF Ceramic, X7R
10
µF Ceramic, X7R/Y5V
10
µF Ceramic, X7R/Y5V
100
nF Ceramic, X7R
82
kΩ 1% (Note 15)
RSO
SO Output Pull-up Resistor
100
kΩ
C_VREF
L_BOOST
D_OUT
RGB1
Reference Voltage Capacitor, between V_REF and GND 100
Boost Converter Inductor
10
Rectifying Diode, V_F @ Maxload
0.3
RGB LED1
nF Ceramic, X7R
µH Shielded, Low ESR, I_SAT ∼1A
V Schottky Diode
RGB2
RGB LED2
R_R1, R_G1, R_B1 Current Limit Resistor
R_R2, R_G2, R_B2 Current Limit Resistor
LEDs
White LEDs
User Defined
(See Application Note AN-1291 for resistor size calculation)
Note 15: Resistor RT accuracy specification change from 1% → 5% will be seen on timing accuracy of RGB block. Also the boost converter’s switching frequency
will be affected.
Control Registers
Control registers and register bits are shown in the following table.
ADDR
REGISTER
D7
D6
D5
D4
00H RGB Control register1 rgb pwm rgb start
rsw1
gsw1
01H
red1_on_off
r1_on[3] r1_on[2] r1_on[1] r1_on[0]
02H
green1_on_off
g1_on[3] g1_on[2] g1_on[1] g1_on[0]
03H
blue1_on_off
b1_on[3] b1_on[2] b1_on[1] b1_on[0]
04H
r1slope, r1duty
r1slope[3] r1slope[2] r1slope[1] r1slope[0]
05H
g1slope, g1duty g1slope[3] g1slope[2] g1slope[1] g1slope[0]
06H
b1slope, b1duty b1slope[3] b1slope[2] b1slope[1] b1slope[0]
07H RGB Control register2 cycle[1] cycle[0] r1_pwm g1_pwm
0BH
enables
nstby en_boost en_flash1
0DH
boost output
boost[7] boost[6] boost[5] boost[4]
2AH
red2_on_off
r2_on[3] r2_on[2] r2_on[1] r2_on[0]
2BH
green2_on_off
g2_on[3] g2_on[2] g2_on[1] g2_on[0]
2CH
blue2_on_off
b2_on[3] b2_on[2] b2_on[1] b2_on[0]
2DH
r2slope, r2duty
r2slope[3] r2slope[2] r2slope[1] r2slope[0]
2EH
g2slope, g2duty g2slope[3] g2slope[2] g2slope[1] g2slope[0]
2FH
b2slope, b2duty b2slope[3] b2slope[2] b2slope[1] b2slope[0]
Default value of each register is 0000 0000 except boost output which is 0011 1111 (5V).
D3
D2
bsw1
rsw2
r1_off[3] r1_off[2]
g1_off[3] g1_off[2]
b1_off[3] b1_off[2]
r1duty[3] r1duty[2]
g1duty[3] g1duty[2]
b1duty[3] b1duty[2]
b1_pwm r2_pwm
en_flash2
boost[3] boost[2]
r2_off[3] r2_off[2]
g2_off[3] g2_off[2]
b2_off[3] b2_off[2]
r2duty[3] r2duty[2]
g2duty[3] g2duty[2]
b2duty[3] b2duty[2]
D1
gsw2
r1_off[1]
g1_off[1]
b1_off[1]
r1duty[1]
g1duty[1]
b1duty[1]
g2_pwm
boost[1]
r2_off[1]
g2_off[1]
b2_off[1]
r2duty[1]
g2duty[1]
b2duty[1]
D0
bsw2
r1_off[0]
g1_off[0]
b1_off[0]
r1duty[0]
g1duty[0]
b1duty[0]
b2_pwm
boost[0]
r2_off[0]
g2_off[0]
b2_off[0]
r2duty[0]
g2duty[0]
b2duty[0]
15
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