cat3604v Catalyst Semiconductor, cat3604v Datasheet - Page 11

• Manufacturer Part Number: cat3604v
• Description: 4-channel Quad-mode? Led Driver With Open/short Led Detection
• Manufacturer: Catalyst Semiconductor

PWM DIMMING
The EN pin is used to provide total Shutdown of the
device as well as High Resolution PWM dimming
control on the LED Channels.
Shutdown of the device occurs after the EN pin has
been held low for 1.5ms. During the “soft-start” power-
up sequence from the shutdown mode, the LED
current typically settles within 40µs (for 1X mode
operation). This LED current settling time becomes
400µs if 1.33X operation is needed (i.e low battery
voltage).
For High Resolution PWM dimming control (typically
frequencies at 2kHz or above), the device will remain
powered and only the LED channels output will be
switched on and off during the PWM (the rest of the
device will remain powered-up). This allows the output
channels to have “instant-on” response, where the
LED current settles within 1µs of the applied PWM
dimming signals. This “instant-on” modes makes the
device suitable for extremely high frequency PWM
dimming schemes.
Figure 5 shows the output current for PWM frequencies
up to 100kHz and with duty cycles of 30% and 70%.
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
11
For best performance, the duty cycle off-time T
should meet the following timing limits:
Figure 5. Output current vs. PWM frequency
for slow frequency ≤ 600Hz, T
for fast frequency ≥ 1kHz, T
100
90
80
70
60
50
40
30
20
10
0.1
70% DC
30% DC
PWM FREQUENCY [kHz]
1
OFF
OFF
≤ 400µs
10
≥ 800µs
Doc. No. MD-5029 Rev. B
CAT3604V
100
OFF