Datasheet

MAX3816A
I
2
C 2-Wire Extender for DDC in DVI,
HDMI, and VGA Interfaces
8 _______________________________________________________________________________________
LOW
STATE
HIGH
STATE
CLOCK_D > 17.5% AND CLOCK_C > 12.5%
CLOCK_C “OR” CLOCK_D < 75%
NOTES:
1) STATE CHANGE CONDITIONS ARE IN ITALICS. TRANSITION ACTIONS ARE UNDERLINED.
2) THE DATA CHANNEL STATE MACHINE IS IDENTICAL AND SYMMETRIC, EXCEPT THAT HOLDOFF TIME IS 2.0μs INSTEAD OF 2.5μs.
ALSO, IN ADDITION TO THE 85% CONDITION TO EXIT STATE 6, DATA HAS AN ADDITIONAL EXIT: DATA_C “OR” DATA_D < 60%.
3) DEPENDENT ON MODE PIN 16: MODE = LOW FOR SERIAL OPERATION (DRIVERS HOLD); MODE = HIGH FOR PARALLEL OPERATION (DRIVERS OFF).
HOLDOFF TIMER = START
HOLDOFF TIMER = START
5
SENSE OFF
DRIVERS ON
6
SENSE OFF
DRIVERS OFF
4
SENSE ON
(NOTE 3)
RAMP
UP
RAMP
DOWN
3
SENSE OFF
(NOTE 3)
1
SENSE ON
DRIVERS OFF
2
SENSE OFF
DRIVERS ON
HOLDOFF TIMER = 1.75 s
μ
HOLDOFF TIMER = 1.75 s
μ
HOLDOFF TIMER ≥ 2.5 s
“AND”
CLOCK_C “AND” CLOCK_D > 85%
μ
HOLDOFF TIMER = 2.5 s
μ
Figure 1a. Clock State Machine Diagram
Locally, connect a 47kΩ pullup resistor from CLOCK_C
and DATA_C to V
CC
. This assumes that a 1.65kΩ
pullup resistor resides at the opposite end of each
channel.
Display Drivers
The display drivers (Figure 11) are typical open-drain
pulldown devices capable of discharging up to 400pF
of capacitive load within the I
2
C fall-time limits.
Locally, connect a 2.2kΩ pullup resistor from CLOCK_D
and DATA_D to V
DD
for V
DD
= 3.3V, or a 3.3kΩ pullup
resistor to V
DD
for V
DD
= 5V.
Level Sense
The MAX3816A’s level-sensing circuitry monitors the
incoming data for state transitions. When the CLOCK or
DATA signal is high and drops below V
TRIGIH
, the con-
troller ramps the outputs low. When the DATA and
CLOCK are low and both rise above V
TRIGI
L
, refer-
enced to GND_REF on the source side or V
SS
on the
display side, the output drives the level high.