PCA9507 データシートの表示（PDF） - NXP Semiconductors.

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PCA9507

2-wire serial bus extender for HDMI DDC I2C-bus and SMBus

NXP Semiconductors. 

NXP Semiconductors

PCA9507

2-wire serial bus extender for HDMI DDC I2C-bus and SMBus

VCC(B)

0.3VCC(B)

port B

0.4 V

VCC(A)

0.3VCC(A)

port A

0.5 V

0V

0.7VCC(A)

0V

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Fig 4. Port A and port B I/O levels

When port B falls first and goes below 0.3VCC(B) the port A driver is turned on and port A

pulls down to 0 V. As port A falls below 0.3VCC(A) the port B pull-down pulls port B down to

about 0.5 V. Port B falls below 0.4 V because it is not possible to know who is driving the

port A LOW, so the PCA9507 direction control assumes that port A is controlling the part

unless port B falls below 0.4 V. When the port B voltage is ≤ 0.4 V the port A driver of the

PCA9507 is on and holds port A down nearly 0 V. As the port B voltage rises because the

external driver turns off, the port B voltage rises up to ~0.5 V because port A is LOW;

once port B rises to ~0.5 V the port A pull-down driver turns off. Then port A rises with a

rise time determined by the RC of port A when it crosses the port A threshold ~0.3VCC(A)

the port B driver is turned off and the rising edge accelerator is turned on, which causes a

faster rising edge until it reaches the turn-off point for the rising edge accelerator

~0.7VCC(A). Then it continues to rise at the slower rate determined by the RC of port A.

When the port B driver turns off, port B rises with the RC of port B.

VCC(A) powers the port A I/Os and the 0.3VCC(A) reference for port A as well as the port A

power good detect circuit. VCC(B) powers the rest of the chip including the port B I/Os and

the support functions. Figure 4 illustrates the threshold and I/O levels for port A and

port B.

6.1 Enable

The EN pin is active HIGH with an internal ~100 kΩ pull-up to VCC(B) and allows the user

to select when the buffer is active. This can be used to isolate the line when the HDMI

DDC transmitter or receiver is not ready, or from a badly behaved slave on power-up until

after the system power-up reset. It should never change state during an I2C-bus operation

because disabling during a bus operation will hang the bus and enabling part way through

a bus cycle could confuse the I2C-bus parts being enabled. The enable pin should only

change state when the global bus and the buffer port are in an idle state to prevent system

failures.

6.2 Rise time accelerators

PCA9507 has rise time accelerators on port A only. During port A positive bus transitions

a current source is switched on to quickly slew the SDAA and SCLA lines HIGH once the

input level of 0.3VCC(A) is exceeded for the PCA9507 and turns off as the 0.7VCC(A)

voltage is approached.

PCA9507_1

Product data sheet

Rev. 01 — 7 February 2008

© NXP B.V. 2008. All rights reserved.

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