CAT4104 Datasheet, PDF (3/13 Pages) ON Semiconductor – 700 mA Quad Channel Constant Current LED Driver

CAT4104
Table 4. RECOMMENDED EN/PWM TIMING (Min and Max values are over the recommended operating conditions unless
specified otherwise. Typical values are at VIN = 5.0 V, T_AMB = 25°C.)
Symbol
Name
Conditions
Min
Typ
Max
Units
T_PS
Turn−On time, EN/PWM rising to I_LED from I_LED = 175 mA
1.5
ms
shutdown
I_LED = 80 mA
1.3
T_P1
Turn−On time, EN/PWM rising to I_LED
I_LED = 175 mA
600
ns
T_P2
Turn−Off time, EN/PWM falling to I_LED
I_LED = 175 mA
400
ns
I_LED = 80 mA
300
T_R
LED rise time
I_LED = 175 mA
700
ns
I_LED = 80 mA
440
T_F
LED fall time
I_LED = 175 mA
360
ns
I_LED = 80 mA
320
T_LO
EN/PWM low time
1
ms
T_HI
EN/PWM high time
5
ms
T_PWRDWN EN/PWM low time to shutdown delay
4
8
ms
EN/PWM
SHUTDOWN
T_P2
T_PS
LED CURRENT
50%
SHUTDOWN 0 mA
T_HI
T_LO
T_PWRDWN
T_P1 T_R
50%
POWERDOWN SHUTDOWN 0 mA
T_F
I_LED
+
1.2 V
R_SET
100
90%
10%
0 mA
QUIESCENT CURRENT
SHUTDOWN 0 mA
Figure 2. CAT4104 EN/PWM Timing
SHUTDOWN 0 mA
EN/PWM Operation
The EN/PWM pin has two primary functions. One
function enables and disables the device. The other function
turns the LED channels on and off for PWM dimming
control. The device has a very fast turn−on time (from
EN/PWM rising to LED on) and allows “instant on” when
dimming LED using a PWM signal.
Accurate linear dimming is compatible with PWM
frequencies from 100 Hz to 5 kHz for PWM duty cycle
down to 1%. PWM frequencies up to 50 kHz 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 1 ms.
To ensure that PWM pulses are recognized, pulse width
low time T_LO should be longer than 1 ms. The CAT4104
enters a “zero current” shutdown mode after a 4 ms delay
(typical) when EN/PWM is held low.
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