CAT3636 Datasheet, PDF (10/15 Pages) Catalyst Semiconductor – 6-Channel Quad-ModeTM Fractional LED Driver in TQFN3x3

CAT3636
REGISTER CONFIGURATION AND PROGRAMMING
Table 1. Register Address and Data
Register
REG1
REG2
REG3
REG4
REG5
REG6
Address
Pulses
1
2
3
4
5
6
Description
Bank Enable and IMODE
Global Current Setting
Bank A Current Setting
Bank B Current Setting
Bank C Current Setting
Return Lockout
Bits
Bit 3
DATA pattern
Bit 2
Bit 1
Bit 0
4
IMODE ENA
ENB
ENC
4
4
See Table 2 for values
4
4
1
RTLKO
Table 2. REG2-5 Current Setting Registers
Data
Pulses
0
REG1-6
Value
(binary)
0000
LED Current
IMODE = 0
0.0mA
LED Current
IMODE = 1
2mA
1
1111
3.75mA
32mA
2
1110
3.5mA
30mA
3
1101
3.25mA
28mA
4
1100
3mA
26mA
5
1011
2.75mA
24mA
6
1010
2.5mA
22mA
7
1001
2.25mA
20mA
8
1000
2mA
18mA
9
0111
1.75mA
16mA
10
0110
1.5mA
14mA
11
0101
1.25mA
12mA
12
0100
1mA
10mA
13
0011
0.75mA
8mA
14
0010
0.5mA
6mA
15
0001
0.25mA
4mA
16
0000
0.0mA
2mA
Register REG1 allows to set the mode and select the
pairs of LEDs to be turned on. A low LED current
mode exists to allow for very low current operation
under 4mA per channel. If IMODE equals 1, the high
current range is selected up to 32mA. If IMODE is set
to 0, all currents are divided by 8. Each bank of LEDs
(A, B or C) can be turned on independently by setting
the respective bit ENA, ENB, ENC to 1.
Register REG2 allows to set the same current for all 6
channels. REG3, REG4, REG5 allow to set the
current respectively in banks A, B and C. The three
banks can be programmed with independent current
values.
REG6 contains the return lockout (RTLKO) bit. This
stops the charge pump returning to 1x mode. One
pulse sets it to 1. Two pulses or no pulses set RTLKO
to 0. When RTLKO is set to 1, the charge pump
cannot automatically return to 1x mode when in one of
the charge pump modes. The device can however
move from 1x to 1.33x to 1.5x to 2x if the input voltage
is not sufficient to drive the programmed LED
currents.
REG6 also triggers a charge pump reset as soon as it
is addressed. This forces the charge pump to start
from 1x mode and reassess the correct mode it
should be in to drive the LEDs most efficiently. If the
input voltage has risen or the device has been
reprogrammed to other LED values, it is
recommended to trigger this reset allowing the charge
pump to run in the most efficient mode.
The CAT3636 enters a “zero current” shutdown mode
if EN/SET is held low for 1.5ms or more. All registers
are reset back to zero when the device is placed in
shutdown.
Doc. No. 5020 Rev. A
10
© 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice