LTC3205_15 Datasheet, PDF (5/16 Pages) Linear Technology – Multidisplay LED Controller

LTC3205
TYPICAL PERFOR A CE CHARACTERISTICS
Input Supply Voltage Required for
Higher LED Currents
3.9
T_A = 25°C
3.7
3.5
I_MS
3.3
3.1
I_RGB
2.9
2.7
2.5
25
50 75 100 125 175 200 225 250
I_MS OR I_RGB CURRENT (µA)
3205 G14
Compliance Voltage for Higher
LED Currents
120
V_IN = 3.6V
T_A = 25°C
100
I_RGB = 250µA
I_RGB = 200µA
80
I_RGB = 150µA
60
I_RGB = 100µA
40
I_RGB = 50µA
20
0
0
0.2
0.4
0.6
0.8
1.0
LED PIN VOLTAGE (V)
3205 G15
RGB LED Turn On and Off
Characteristics
I_LED
3mA/DIV
0mA
5µs/DIV
3205 G011
PI FU CTIO S
MAIN1-MAIN4 (Pins 2, 1, 24, 23): Current Source
Outputs for the Main Display White LEDs. The current for
the main display is controlled by the resistor on the I_MS
pin. The LEDs on the main display can be set to 100%,
50%, 25% or 0% of full-scale programmed current under
software control. See Tables 1 and 2.
C1⁺, C1^–, C2⁺, C2^– (Pins 5, 4, 6, 3): Charge Pump Flying
Capacitor Pins. A 1µF X7R or X5R ceramic capacitor should be
connected from C1⁺ to C1^– and another from C2⁺ to C2^–.
D_IN (Pin 7): Input Data for the 16-Bit Serial Port. Serial data
is shifted in one bit per clock to control the LTC3205 (see
Table 1). The logic level for D_IN is referenced to DV_CC.
SCLK (Pin 8): Clock Input for the 16-Bit Serial Port (see
Figure 3). The logic level for SCLK is referenced to DV_CC.
LD (Pin 9): Load Input for the 16-Bit Serial Port. Command
data is loaded into the command latch on the falling edge
of LD (see Figure 3). The logic level for LD is referenced to
DV_CC.
ENRGB (Pin 10): This pin is used to enable and disable the
red, green and blue current sources. Once ENRGB is brought
high, the LTC3205 illuminates the RGB display with the color
combination that was previously programmed via the serial
port. When the main and sub displays are off and ENRGB is
low, the LTC3205 will be in shutdown. The logic level for
ENRGB is referenced to DV_CC.
STEPUP (Pin 11): A logic high on this pin forces the
LTC3205’s charge pump to operate in 2:3 step-up mode,
thereby eliminating any possibility of the device switching
from 1:1 mode to 2:3 mode during critical communication
periods. The logic level for STEPUP is referenced to DV_CC.
DV_CC (Pin 12): This pin sets the logic reference level of the
LTC3205.
I_RGB (Pin 13): This pin controls the amount of LED current
at the RED, GREEN and BLUE LED pins. The I_RGB pin
servos to 1.223V when there is a resistor to ground. The
current in the RED, GREEN and BLUE LEDs will be 400
times the current at the I_RGB pin when programmed to full
scale (see Tables 1 and 3).
I_MS (Pin 14): This pin controls the maximum amount of
LED current in both the main and sub LED displays. The
I_MS pin servos to 1.223V when there is a resistor to
ground. The currents in the main and sub display LEDs will
be 100, 200 or 400 times the current at the I_MS pin
depending on which setting is chosen from the serial port.
CPO (Pin 15): Output of the Charge Pump. This output
should be used to power white, blue and “true” green
LEDs. Red LEDs can be powered from V_IN or CPO. An X5R
or X7R low impedance (ceramic) 1µF charge storage
capacitor is required on CPO.
3205f
5