CAT3636 Datasheet, PDF (10/14 Pages) Catalyst Semiconductor – 6-Channel Quad-ModeTM Fractional LED Driver in TQFN3x3

CAT3636
Register Configuration and Programming
Table 6. 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
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 4 mA per
channel. If IMODE equals 1, the high current range is
selected up to 32 mA. 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, as shown in Table 7. For example, to enable all 6
LEDs in low current mode, REG1 is programmed to 0111
binary (9 data pulses).
Table 7. REG1 REGISTER SETTING
Data
Pulses
REG1 Value
(binary)
IMODE
Bank Enable
ENA ENB ENC
0
0000
0
−
−
−
1
1111
1
On On On
2
1110
1
On On
−
3
1101
1
On
−
On
4
1100
1
On
−
−
5
1011
1
−
On On
6
1010
1
−
On
−
7
1001
1
−
−
On
8
1000
1
−
−
−
9
0111
0
On On On
10
0110
0
On On
−
11
0101
0
On
−
On
12
0100
0
On
−
−
13
0011
0
−
On On
14
0010
0
−
On
−
15
0001
0
−
−
On
16
0000
0
−
−
−
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.
DATA Pattern
Bits
Bit 3
Bit 2
Bit 1
Bit 0
4
IMODE
ENA
ENB
ENC
4
4
See Table 8 for values
4
4
1
RTLKO
Table 8. REG2−5 CURRENT SETTING REGISTERS
Data
Pulses
REGx Value
(binary)
LED Current
IMODE = 0
LED Current
IMODE = 1
0
0000
1
1111
2
1110
3
1101
4
1100
5
1011
6
1010
7
1001
8
1000
9
0111
10
0110
11
0101
12
0100
13
0011
14
0010
15
0001
16
0000
0.0 mA
3.75 mA
3.5 mA
3.25 mA
3 mA
2.75 mA
2.5 mA
2.25 mA
2 mA
1.75 mA
1.5 mA
1.25 mA
1 mA
0.75 mA
0.5 mA
0.25 mA
0.0 mA
2 mA
32 mA
30 mA
28 mA
26 mA
24 mA
22 mA
20 mA
18 mA
16 mA
14 mA
12 mA
10 mA
8 mA
6 mA
4 mA
2 mA
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 1.5 ms or more. All registers are
reset back to zero when the device is placed in shutdown.
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