PCA9521D,118 NXP Semiconductors, PCA9521D,118 Datasheet - Page 4

• Manufacturer Part Number: PCA9521D,118
• Description: Interface - Signal Buffers, Repeaters
• Manufacturer: NXP Semiconductors
• Series: PCA9521r

Specifications of PCA9521D,118

• Rohs: yes
• Operating Supply Voltage: 2.7 V to 5.5 V
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-8
• Input Capacitance: 10 pF
• Maximum Clock Frequency: 1 MHz
• Maximum Operating Frequency: 1000 kHz
• Operating Current: 6 mA
• Power Dissipation: 300 mW
• Product Type: Buffers
• Propagation Delay Time: 45 ns
• Tx/rx Type: I2C, PMBus, SMBus

NXP Semiconductors
7. Functional description
PCA9521
Product data sheet
7.1 V
7.2 SA1, SA2, SB1, SB2 — buffer inputs/outputs
7.3 EN — enable; activate buffer operations
Refer to
The power supply voltage for the PCA9521 may be any voltage in the range 2.7 V to
5.5 V. The threshold level below which the output will begin to match the input is 33 % of
V
switching threshold, and noise margins, in mind.
The two buffers (SA and SB) are identical and symmetrical. The buffers can be driven
from either direction, with the same response. When port 1 of the buffer is being driven
LOW (< 0.3V
provide the buffered output.
The ‘input’ side is determined by the lowest externally driven signal. Therefore if port 1 is
externally pulled to V
buffer will pull port 2 down further such that it becomes V
subsequently become lower than port 1 by the amount of the offset voltage
(V
buffering operation will switch, and port 2 will become the ‘input’. The voltage at port 1 will
then become V
an offset voltage) the external devices are effectively in control.
The enable input, EN, is used to disable the buffer, for the purpose of isolating sections of
the bus. The IC should only be disabled when the bus is idle. This prevents truncation of
commands which may confuse other devices on the bus.
Enable may also be used to progressively activate sections of the bus during system
start-up. Bus sections slow to respond on power-up can be kept isolated from the main
system to avoid interference and collisions.
The EN pin may be pulled up higher than the V
capability of the PCA9521 in a level shifting role. For example, a microprocessor could
drive EN, SA1 and SB1 at 5 V, while the buffer V
Similarly, the threshold level of the EN pin allows a 1.8 V device to disable a PCA9521
with a V
The EN pin includes an internal 2 A pull-down current, which will act to disable the
device should the pin be left floating.
CC
CC
Sx2
. Hence, the operating voltage should be chosen with the required bus voltage,
, GND — supply pins
+ V
CC
Figure 1 “Block
offset
of 3.3 V.
CC
< V
Sx1
) by another device on the bus, port 2 will be driven LOW by the IC to
All information provided in this document is subject to legal disclaimers.
Sx1
= V
) by means of an external device pulling it LOW, control of the
Sx1
Sx2
Rev. 2 — 19 March 2013
diagram”.
= 250 mV, and port 2 is externally pulled to V
+ V
offset
. When both ports are being held almost equal (less than
CC
CC
of the buffer, further enhancing the
, SA2 and SB2 ports are at 3.3 V.
Fast dual bidirectional bus buffer
Sx2
= V
Sx1
+ V
Sx2
PCA9521
offset
© NXP B.V. 2013. All rights reserved.
= 500 mV, the
. Should port 2
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