CAT4101_12 Datasheet, PDF (3/9 Pages) ON Semiconductor – 1 A Constant-Current LED Driver

CAT4101
Table 4. RECOMMENDED EN/PWM TIMING
(For 3.0 V ≤ VIN ≤ 5.5 V, over full ambient temperature range −40°C to +85°C.)
Symbol
Name
Conditions
Min
Typ
Max
T_PS
Turn−On time, EN/PWM rising to I_LED from
I_LED = 1 A
1.6
Shutdown
I_LED = 350 mA
1.1
T_P1
Turn−On time, EN/PWM rising to I_LED
I_LED = 1 A
920
I_LED = 350 mA
620
T_P2
Turn−Off time, EN/PWM falling to I_LED
I_LED = 1 A
440
I_LED = 350 mA
310
T_R
LED rise time
I_LED = 1 A
840
I_LED = 350 mA
390
T_F
LED fall time
I_LED = 1 A
470
I_LED = 350 mA
350
T_LO
EN/PWM low time
1
T_HI
EN/PWM high time
5
T_PWRDWN EN/PWM low time to shutdown delay
8
EN/PWM
SHUTDOWN
T_P2
T_PS
LED CURRENT
50%
SHUTDOWN 0 mA
T_HI
T_LO
T_PWRDWN
T_P1
50%
T_F
T_R
90%
10%
I_LED = (1.2 V / R_SET) x 400
0 mA
Units
ms
ns
ns
ns
ns
ms
ms
ms
SHUTDOWN
VIN QUIESCENT CURRENT
SHUTDOWN 0 mA
Figure 2. CAT4101 EN/PWM Timing
SHUTDOWN
EN/PWM Operation
The EN/PWM pin has two primary functions. One
function enables and disables the device. The other function
turns the LED channel 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 CAT4101
enters a “zero current” shutdown mode after a 5 ms delay
(typical) when EN/PWM is held low.
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