PCA9509GM

电平转换I2C总线/ SMBus的中继 Level translating I2C-bus/SMBus repeater

Overview

The PCA9509 is a level translating I²C-bus/SMBus repeater that enables processor low voltage 2-wire serial bus to interface with standard I²C-bus or SMBus I/O. While retaining all the operating modes and features of the I²C-bus system during the level shifts, it also permits extension of the I²C-bus by providing bidirectional buffering for both the data SDA and the clock SCL lines, thus enabling the I²C-bus or SMBus maximum capacitance of 400 pF on the higher voltage side. Port A allows a voltage range from 1.35 V to VCCB ‑ 1.0 V and requires no external pull-up resistors due to the internal current source. Port B allows a voltage range from 3.0 V to 5.5 V and is overvoltage tolerant. Both port A and port B SDA and SCL pins are high-impedance when the PCA9509 is unpowered.

For applications where Port A VCCA is less than 1.35 V or Port B VCCB is less than 3.0 V, use drop-in replacement PCA9509A.

The bus port B drivers are compliant with SMBus I/O levels, while port A uses a current sensing mechanism to detect the input or output LOW signal which prevents bus lock-up. Port A uses a 1 mA current source for pull-up and a 200 Ω pull-down driver. This results in a LOW on the port A accommodating smaller voltage swings. The output pull-down on the port A internal buffer LOW is set for approximately 0.2 V, while the input threshold of the internal buffer is set about 50 mV lower than that of the output voltage LOW. When the port A I/O is driven LOW internally, the LOW is not recognized as a LOW by the input. This prevents a lock-up condition from occurring. The output pull-down on the port B drives a hard LOW and the input level is set at 0.3 of SMBus or I²C-bus voltage level which enables port B to connect to any other I²C-bus devices or buffer.

The PCA9509 drivers are not enabled unless VCCA is above 0.8 V and VCCB is above 2.5 V. The enable EN pin can also be used to turn on and turn off the drivers under system control. Caution should be observed to change only the state of the EN pin when the bus is idle.

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## Features

* Bidirectional buffer isolates capacitance and allows 400 pF on port B of the device

* Voltage level translation from port A 1.35 V to VCCB ‑ 1.0 V to port B 3.0 V to 5.5 V

* Requires no external pull-up resistors on lower voltage port A

* Active HIGH repeater enable input

* Open-drain inputs/outputs

* Lock-up free operation

* Supports arbitration and clock stretching across the repeater

* Accommodates Standard-mode and Fast-mode I²C-bus devices and multiple masters

* Powered-off high-impedance I²C-bus pins

* Operating supply voltage range of 1.35 V to VCCB ‑ 1.0 V on port A, 3.0 V to 5.5 V on port B

* 5 V tolerant port B SCL, SDA and enable pins

* 0 Hz to 400 kHz clock frequency

**Remark**: The maximum system operating frequency may be less than 400 kHz because of the delays added by the repeater.

* ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per JESD22-C101

* Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

* Packages offered: TSSOP8, SO8, XQFN8

## Features