cat4109 ON Semiconductor, cat4109 Datasheet - Page 3

• Manufacturer Part Number: cat4109
• Description: 3-channel Constant-current Rgb Led Driver With Individual Pwm Dimming
• Manufacturer: ON Semiconductor

RECOMMENDED TIMING
Min and Max values are over recommended operating conditions unless specified otherwise.
Typical values are at VDD = 5.0V, T
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
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.
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
Symbol Name
T
PWRDWN
Output Enable
LED Current
VIN Quiescent Current
T
T
T
T
T
T
T
PS
LO
P1
P2
HI
R
F
Turn-On time, OE rising to I
Shutdown
Turn-On time, OE or PWMx rising to
I
Turn-Off time, OE or PWMx falling to
I
LED rise time
LED fall time
OE low time
OE high time
OE low time to shutdown delay
SHUTDOWN 0mA
SHUTDOWN 0mA
SHUTDOWN
T
PS
PWRDWN
T
P2
50%
, the device enters
AMB
LED
= 25°C
T
Figure 1. CAT4109 OE Timing
from
HI
50%
T
P1
T
LO
T
Conditions
I
I
I
I
I
R
LED
LED
LED
LED
LED
90%
10%
3
= 100mA
= 100mA
= 100mA
= 100mA
= 100mA
T
F
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
in the range of 1µs.
To ensure that PWM pulses are recognized, pulse
width low time T
driver enters a “zero current” shutdown mode after a
4ms delay (typical) when OE is held low.
I
LED
= (1.2V/R
Min
1
5
SET
LO
) x 400
should be longer than 1μs. The
Typ
600
300
300
300
1.4
4
T
0mA
PWRDWN
Max
8
Doc. No. MD-5042, Rev. A
PS
SHUTDOWN 0mA
SHUTDOWN 0mA
is very short,
CAT4109
Units
ms
μs
ns
ns
ns
ns
μs
μs