PCA9509AGM,125 NXP Semiconductors, PCA9509AGM,125 Datasheet - Page 5

• Manufacturer Part Number: PCA9509AGM,125
• Description: Interface - Signal Buffers, Repeaters I2CbusSMBus repeater
• Manufacturer: NXP Semiconductors

Specifications of PCA9509AGM,125

• Rohs: yes
• Operating Supply Voltage: 0.8 V to 5.5 V
• Mounting Style: SMD/SMT
• Package / Case: XQFN-8
• Logic Type: I2C, SMBus
• Maximum Clock Frequency: 400 KHz
• Maximum Operating Frequency: 400 KHz
• Power Dissipation: 100 mW
• Factory Pack Quantity: 4000

NXP Semiconductors
6. Functional description
PCA9509A
Product data sheet
6.1 Enable
Refer to
The PCA9509A enables I
without degradation of system performance. The PCA9509A contains 2 bidirectional
open-drain buffers specifically designed to support up-translation/down-translation
between the low voltage and 3.3 V SMBus or 5 V I
overvoltage tolerant to 5.5 V even when the device is unpowered. Due to the current
source on port A the voltage on the pins should not be above V
powered.
The PCA9509A includes a power-up circuit that keeps the output drivers turned off until
V
any sequence at power-up. After power-up and with the EN pin HIGH, a LOW level on
port A (below approximately 0.15V
or SCL) on and drives port B down to about 0 V. When port A rises above approximately
0.15V
the pin HIGH. When port B falls first and goes below 0.3V
on and port A pulls down to 0.2V
the port A voltage goes below V
pull-down driver is enabled until port A rises above approximately 0.15V
port B, if not externally driven LOW, will continue to rise being pulled up by the external
pull-up resistor.
Remark: Ground offset between the PCA9509A ground and the ground of devices on
port A of the PCA9509A must be avoided.
The reason for this cautionary remark is that a CMOS/NMOS open-drain capable of
sinking 3 mA of current at 0.4 V has an output resistance of 133  or less (R = E / I). Such
a driver shares enough current with the port A output pull-down of the PCA9509A to be
seen as a LOW as long as the ground offset is zero. If the ground offset is greater than
0 V, then the driver resistance must be less. Since V
temperatures and the low end of the current distribution, the maximum ground offset
should not exceed 40 mV.
Bus repeaters that use an output offset are not interoperable with the port A of the
PCA9509A as their output LOW levels are not recognized by the PCA9509A as a LOW. If
the PCA9509A is placed in an application where the V
not go below its V
Port B provides normal I
masters and repeaters.
The EN pin is active HIGH and allows the user to select when the repeater is active. This
can be used to isolate a badly behaved slave on power-up until after the system power-up
reset. It should never change state during an I
a bus operation hangs the bus and enabling part way through a bus cycle could confuse
the I
to reduce power consumption.
CC(B)
2
C-bus parts being enabled. The EN also puts the PCA9509A in a standby condition
CC(A)
is above 1.7 V and the V
Figure 1 “Functional diagram of
, the port B pull-down driver is turned off and the external pull-up resistor pulls
All information provided in this document is subject to legal disclaimers.
IL
, the port B does not go LOW.
Rev. 1 — 29 February 2012
2
C-bus voltage levels and is interoperable with all I
2
C-bus or SMBus translation down to V
CC(A)
IL
CC(A)
Low power level translating I
. If the port A low voltage goes below V
CC(A)
is above 0.7 V. V
(typical). The port B pull-down is not enabled unless
) turns the corresponding port B driver (either SDA
PCA9509A”.
2
C-bus operation because disabling during
2
C-bus. The port A and port B I/Os are
IL
CC(B)
can be as low as 80 mV at cold
IL
of port A of the PCA9509A does
CC(B)
and V
, the port A driver is turned
CC(A)
2
CC(A)
CC(A)
C-bus/SMBus repeater
PCA9509A
when the device is
as low as 0.8 V
can be applied in
© NXP B.V. 2012. All rights reserved.
CC(A)
IL
, the port B
2
C-bus slaves,
(V
IL
), then
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