TPS60230_14 Datasheet, PDF (12/21 Pages) Texas Instruments – WHITE LED CHARGE PUMP CURRENT SOURCE WITH PWM BRIGHTNESS CONTROL

TPS60230
SLVS516A – MAY 2004 – REVISED JUNE 2004
APPLICATION INFORMATION
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TYPICAL APPLICATION OF A SMART PHONE DISPLAY WITH RESISTORS CONNECTED IN
PARALLEL
If more than 25 mA of output current is needed, then the input pins to the current sinks can be connected in
parallel as shown in the following application figure. This method can also be used to connect a LC display with
only two connections for the white LEDs.
VIN = 2.7 V
to 6.5 V
1 mF
0.47 mF
0.47 mF
VIN
VOUT
C1+
D1
C1−
D2
D3
C2+
D4
C2−
D5
EN1
EN2
ISET
GND
PGND
1 mF
Typical Smartphone Display
Figure 12. Typical Application With Resistors in Parallel
ANALOG DIMMING USING ISET PIN
The ISET pin can be used to connect an analog dc signal in the range of 0 mV to 600 mV (EN1 = EN2 = 1) for
analog dimming of the white LEDs. For an input voltage of 0 V at ISET, the current is at its maximum, whereas at
600 mV, the LED current is zero. The maximum current is:
• For EN2 = EN1 = 1: ILED = Vset/Rset × K = 0.6V/6kR × 270 = 27 mA per LED
• For EN2 = 1, EN0 = 1: ILED = Vset/Rset × K = 0.4V/6kR × 270 = 18 mA per LED
• For EN2 = 0, EN1 = 1: ILED = Vset/Rset × K = 0.2V/6kR × 270 = 9 mA per LED
• With EN2, EN1 set to 10 or 01, a voltage of 400 mV or 200 mV is required to set the LED current to zero.
VIN = 2.7 V
to 6.5 V
1 mF
0.47 mF
0.47 mF
VIN
VOUT
C1+
D1
C1−
D2
D3
C2+
D4
C2−
D5
EN1
EN2
GND
ISET
PGND
6 kW
1 mF
V = 0 mV to
600 mV
Figure 13. Analog Dimming Connections Using ISET Pin
TYPICAL APPLICATION USING 2 WHITE LEDs AND 6 GREEN LEDs FOR LCD BACKLIGHT AND
12