Datasheet

PCA9507_1 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 01 — 7 February 2008 5 of 20
NXP Semiconductors
PCA9507
2-wire serial bus extender for HDMI DDC I
2
C-bus and SMBus
6.3 Resistor pull-up value selection
6.3.1 Port A (SDAA and SCLA)
SDAA and SCLA are open-drain I/O that have rise time accelerators and strong pull-down.
When the inputs transition above 0.3V
CC(A)
, the rise time accelerator activates and boosts
the pull-up current during rising edge to meet the I
2
C-bus rise time specification when the
device drives a long cable or heavier capacitance load. The strong pull-down enables the
output to drive to nearly zero voltage for logic LOW. The selection for pull-up resistors are
defined in the HDMI DDC specification shown in Table 3. For HDMI transmitter
applications like digital video player, recorder, or set-top box, the pull-up resistor is in the
range of 1.5 kΩ to 2 kΩ. For HDMI receiver applications like in LCD TV or video card, the
pull-up resistor is 47 kΩ on the SCLA line, and there is no pull-up on the SDAA line.
Please refer to Table 3, Figure 7 and Figure 8 for more details. Figure 5 shows the port A
pull-up resistor values (in kΩ) versus capacitance load (in nF) for 5 V supply voltage
complied with 1 µs rise time per I
2
C-bus Standard-mode specification. The graph
contrasts a shaded and unshaded region. Any resistor value chosen within the unshaded
region would comply with 1 µs rise time, while any value chosen in the shaded region
would not.
Table 3. HDMI DDC pull-up resistors specification
Pin Where Minimum Maximum
SDAA at the source (DVD/STB) 1.5 kΩ 2.0 kΩ
at the sink (LCD TV) - -
SCLA at the source (DVD/STB) 1.5 kΩ 2.0 kΩ
at the sink (LCD TV) 47 kΩ±10 %
rise time = 1 µs; V
CC(A)
=5V
Fig 5. SDAA/SCLA line pull-up resistor versus load capacitance
C
L
(nF)
0 4.03.02.01.0
002aad620
4.5
6.5
2.5
8.5
10.5
R
PU
(kΩ)
0.5
does not comply with
1 µs rise time
complies with
1 µs rise time