MAX6967 MAXIM [Maxim Integrated Products], MAX6967 Datasheet - Page 18

• Manufacturer Part Number: MAX6967
• Description: 10-Port Constant-Current LED Drivers and I/O Expanders with PWM Intensity Control
• Manufacturer: MAXIM [Maxim Integrated Products]

10-Port Constant-Current LED Drivers and I/O
Expanders with PWM Intensity Control
The global current register sets the full (maximum) con-
stant current sunk into an I/O port
put port’s individual constant-current sink can be set to
be either half or full global current by the output current
registers (Table 7). By default, maximum current is
20mA, so the default half current is 10mA.
The MAX6966/MAX6967 provide automatic controls
that allow the currents’ outputs to be ramped down into
automatic shutdown (ramp-down), and ramped up
again out of shutdown (ramp-up) without further inter-
action (Figures 4 and 5). Ramp-down comprises a pro-
grammable hold-off delay, which also maintains the
outputs at full current for a time before the programmed
Table 8. Global Current Register Format
Figure 5. Ramp-Down, Hold-Off, and Fade-Off Behavior
18
Full current is 2.5mA; half current is
1.25mA
Full current is 5mA; half current is 2.5mA
Full current is 7.5mA; half current is
3.75mA
Full current is 10mA; half current is 5mA
Full current is 12.5mA; half current is
6.25mA
Full current is 15mA; half current is 7.5mA
Full current is 17.5mA; half current is
8.75mA
Full current is 20mA; half current is 10mA
______________________________________________________________________________________
GLOBAL CURRENT
Ramp-Up and Ramp-Down Controls
1/4s 1/2s
1/8s
1/16s
REGISTER
ZERO TO 4s HOLD-OFF DELAY BEFORE FADE-OFF
1s
Global Current Register
2s
(Table 8). Each out-
R/W
X
X
X
X
X
X
X
X
0
1
CODE (HEX)
ADDRESS
ZERO TO 8s CURRENT RAMP-DOWN
0x15
4s
1/4s 1/2s
fade-off time, during which the currents’ outputs are
ramped down.
D7
Figure 4. Ramp-Up Behavior
1/8s
1/16s
X
X
X
X
X
X
X
X
X
0
ZERO TO 4s CURRENT FADE-OFF AFTER HOLD-OFF DELAY
1/4s 1/2s
1/8s
1/16s
D6
X
0
X
X
X
X
X
X
X
X
EXIT SHUTDOWN COMMAND
1s
D5
X
X
X
X
X
X
X
X
X
0
ZERO TO 4s CURRENT RAMP-UP AFTER CS RUN
1s
REGISTER DATA
2s
D4
X
0
X
X
X
X
X
X
X
X
2s
D3
X
X
X
X
X
X
X
X
X
0
ISET2 ISET1 ISET0
ISET2 ISET1 ISET0
D2
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
4s
4s
D0
0
1
0
1
0
1
0
1