PCA9509AGM数据手册恩XP中文资料规格书

描述 Description

The PCA9509A is a level translating I²C-bus/SMBus repeater with two voltage suppliesthat enables processor low voltage 2-wire serial bus to interface with standard I²C-bus orSMBus I/O. While retaining all the operating modes and features of the I²C-bus systemduring the level shifts, it also permits extension of the I²C-bus by providing bidirectionalbuffering for both the data (SDA) and the clock (SCL) lines, thus enabling the I²C-bus orSMBus maximum capacitance of 400 pF on the higher voltage side. Port A allows avoltage range from 0.8 V to 1.5 V and requires no external pull-up resistors due to theinternal current source. Port B allows a voltage range from 2.3 V to 5.5 V and isovervoltage tolerant. Both port A and port B SDA and SCL pins are high-impedance whenthe PCA9509A is unpowered.
The bus port B drivers are compliant with SMBus I/O levels, while port A uses an offsetLOW which prevents bus lock-up and allows the bidirectional nature of the device. Port Auses a current source for pull-up and an offset pull-down driver. This results in a LOW onthe port A accommodating smaller voltage swings. The output pull-down on the port Ainternal buffer LOW is set for approximately 0.2 VCC(A), while the input threshold of theinternal buffer is set about 50 mV lower than that of the output voltage LOW. When theport 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 Bdrives a hard LOW and the input level is set at 30 % of SMBus or I²C-bus voltage levelwhich enables port B to connect to any other I²C-bus devices or buffer.
The PCA9509A drivers are not enabled unless VCC(A) is above 0.7 V and VCC(B) is above1.7 V. The enable (EN) pin can also be used to turn the drivers on and off under systemcontrol. Caution should be observed to only change the state of the EN pin when the busis idle.
The PCA9509A is similar to the PCA9509 but offers lower A port voltage range to 0.8 V toaccommodate lower voltage processors and disables the current mirrors when disabled toreduce standby power.
Selection recommendationsThe PCA9509A is recommended for all applications except in the following cases:PCA9509P should be used if an external A-port pull-up resistor is required to adjustcurrent for noise margin considerations or to reduce operating current consumptioneven more.
The PCA9509 should be used if instant on from disable is required with A Port voltagegreater than 1.0 V and larger standby current is not a concern.

Table 1. Device selection recommendationConcern
Recommended device
PCA9509
PCA9509A
PCA9509P
A-port — lowest voltage
0.95 V with limitations
0.80 V
0.80 V
A-port — current source [1]
yes — 1 mA
yes — 270 μA
no — external pull-up
operating current [2]
< 6.1 mA
< 1.9 mA
< 0.95 mA
standby current EN = LOW
< 2 mA
< 10 μA max.
< 10 μA max.
[1] The PCA9509 current mirrors do not shut down when the device is disabled allowing instant turn-on, but atthe cost of the higher standby current. The PCA9509A and PCA9509P current mirrors are turned off whendisabled for lowest standby power consumption, but sufficient delay (10 μs) after enable is needed beforeresuming operation.
[2] Operating currents do not include the current consumed by the external pull-ups on B-port or the externalpull-ups on the A-port of the PCA9509P.

特性 Features

Bidirectional buffer isolates capacitance and allows 400 pF on port B of the device
Voltage level translation from port A (0.8 V to 1.5 V) to port B (2.3 V to 5.5 V)
Requires no external pull-up resistors on lower voltage port A
Active HIGH repeater enable input disables current mirrors and current source toreduce standby power
Open-drain port B 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 0.8 V to 1.5 V on port A, 2.3 V to 5.5 V on port B
All pins are 5 V tolerant with respect to ground pin
0 Hz to 400 kHz clock frequency
Remark: The maximum system operating frequency may be less than 400 kHzbecause 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, XQFN8