CAT4109V-GT2 Datasheet, PDF (3/11 Pages) ON Semiconductor – 3-Channel Constant-Current RGB LED Driver with Individual PWM Dimming

CAT4109
RECOMMENDED TIMING
Min and Max values are over recommended operating conditions unless specified otherwise.
Typical values are at VDD = 5.0V, T_AMB = 25°C
Symbol Name
Conditions
Min
Typ
T_PS
Turn-On time, OE rising to I_LED from
Shutdown
I_LED = 100mA
1.4
T_P1 ^{Turn-On time, OE or PWMx rising to}
I_LED = 100mA
600
T_P2 ^{TI urn-Off time, OE or PWMx falling to}
I_LED = 100mA
300
T_R LI ED rise time
I_LED = 100mA
300
T_F LED fall time
I_LED = 100mA
300
T_LO OE low time
1
T_HI OE high time
5
T_PWRDWN OE low time to shutdown delay
4
Max
8
Units
μs
ns
ns
ns
ns
μs
μs
ms
Output Enable
SHUTDOWN
T_P2
T_PS
LED Current
50%
T_HI
T_LO
T_P1
50%
T_F
T_R
90%
T_PWRDWN
I_LED = (1.2V/R_SET) x 400
SHUTDOWN 0mA
SHUTDOWN 0mA
10%
0mA
VIN Quiescent Current
SHUTDOWN 0mA
Figure 1. CAT4109 OE Timing
SHUTDOWN 0mA
OE OPERATION
The Output Enable (OE) pin has two primary
functions. When the OE input goes from high to low,
all three LED channels are turned off. If OE remains
low for longer than T_PWRDWN, the device enters
shutdown mode drawing “zero current” from the
supply.
The OE input can be used to adjust the contrast of
the RGB LED by applying an external PWM signal.
The device has a very fast turn-on time (from OE
rising to LED on) allowing “instant on” when dimming
LEDs.
When applying PWM signals to the three PWMx
inputs and using the OE pin for dimming, the OE
PWM frequency should be much lower to preserve
the color mixing.
Accurate linear dimming on OE is compatible with
PWM frequencies from 100Hz to 5kHz for PWM duty
cycle down to 1%. PWM frequencies up to 50kHz can
be supported for duty cycles greater than 10%.
When performing a combination of low frequencies
and small duty cycles, the device may enter
shutdown mode. This has no effect on the dimming
accuracy, because the turn-on time T_PS is very short,
in the range of 1µs.
To ensure that PWM pulses are recognized, pulse
width low time T_LO should be longer than 1μs. The
driver enters a “zero current” shutdown mode after a
4ms delay (typical) when OE is held low.
© 2009 SCILLC. All rights reserved.
3
Characteristics subject to change without notice
Doc. No. MD-5042, Rev. A