Data Sheet

PCA9541A
2-to-1 I2C-bus master selector with interrupt logic and reset
Rev. 5 — 24 April 2014
Product data sheet
1. General description
The PCA9541A is a 2-to-1 I2C-bus master selector designed for high reliability dual
master I2C-bus applications where system operation is required, even when one master
fails or the controller card is removed for maintenance. The two masters (for example,
primary and back-up) are located on separate I2C-buses that connect to the same
downstream I2C-bus slave devices. I2C-bus commands are sent by either I2C-bus master
and are used to select one master at a time. Either master at any time can gain control of
the slave devices if the other master is disabled or removed from the system. The failed
master is isolated from the system and does not affect communication between the
on-line master and the slave devices on the downstream I2C-bus.
Two versions are offered for different architectures. PCA9541A/01 with channel 0
selected at start-up, and PCA9541A/03 with no channel selected after start-up.
The interrupt outputs are used to provide an indication of which master has control of the
bus. One interrupt input (INT_IN) collects downstream information and propagates it to
the 2 upstream I2C-buses (INT0 and INT1) if enabled. INT0 and INT1 are also used to let
the previous bus master know that it is not in control of the bus anymore and to indicate
the completion of the bus recovery/initialization sequence. If the masking option is set,
those interrupts can be disabled and do not generate an interrupt.
A bus recovery/initialization if enabled sends nine clock pulses, a not acknowledge, and a
STOP condition in order to set the downstream I2C-bus devices to an initialized state
before actually switching the channel to the selected master.
An interrupt is sent to the upstream channel when the recovery/initialization procedure is
completed.
An internal bus sensor senses the downstream I2C-bus traffic and generates an interrupt
if a channel switch occurs during a non-idle bus condition. This function is enabled when
the PCA9541A recovery/initialization is not used. The interrupt signal informs the master
that an external I2C-bus recovery/initialization must be performed. It can be disabled and
an interrupt is not generated.
The pass gates of the switches are constructed such that the VDD pin can be used to limit
the maximum high voltage, which will be passed by the PCA9541A. This allows the use of
different bus voltages on each pair, so that 1.8 V, 2.5 V, or 3.3 V devices can communicate
with 5 V devices without any additional protection.
The PCA9541A does not isolate the capacitive loading on either side of the device, so the
designer must take into account all trace and device capacitances on both sides of the
device, and pull-up resistors must be used on all channels.
External pull-up resistors pull the bus to the desired voltage level for each channel. All I/O
pins are 6.0 V tolerant.
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
An active LOW reset input allows the PCA9541A to be initialized. Pulling the RESET pin
LOW resets the I2C-bus state machine and configures the device to its default state as
does the internal Power-On Reset (POR) function.
2. Features and benefits
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2-to-1 bidirectional master selector
I2C-bus interface logic; compatible with SMBus standards
PCA9541A/01 powers up with Channel 0 selected
PCA9541A/03 powers up with no channel selected and either master can take control
of the bus
Active LOW interrupt input
2 active LOW interrupt outputs
Active LOW reset input
4 address pins allowing up to 16 devices on the I2C-bus
Channel selection via I2C-bus
Bus initialization/recovery function
Bus traffic sensor
Low Ron switches
Allows voltage level translation between 1.8 V, 2.5 V, 3.3 V and 5 V buses
No glitch on power-up
Supports hot insertion
Software identical for both masters
Low standby current
Operating power supply voltage range of 2.3 V to 5.5 V
6.0 V tolerant inputs
0 Hz to 400 kHz clock frequency
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: SO16, TSSOP16, HVQFN16
3. Applications
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PCA9541A
Product data sheet
High reliability systems with dual masters
Gatekeeper multiplexer on long single bus
Bus initialization/recovery for slave devices without hardware reset
Allows masters without arbitration logic to share resources
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
4. Ordering information
Table 1.
Ordering information
Type number
Topside
marking
Package
Name
Description
Version
PCA9541AD/01
PCA9541AD/1
SO16
plastic small outline package; 16 leads; body width 3.9 mm
SOT109-1
PCA9541AD/03
PCA9541AD/3
SO16
plastic small outline package; 16 leads; body width 3.9 mm
SOT109-1
PCA9541APW/01 9541A/1
TSSOP16
plastic thin shrink small outline package; 16 leads;
body width 4.4 mm
SOT403-1
PCA9541APW/03 9541A/3
TSSOP16
plastic thin shrink small outline package; 16 leads;
body width 4.4 mm
SOT403-1
PCA9541ABS/01
41A1
HVQFN16
plastic thermal enhanced very thin quad flat package;
no leads; 16 terminals; body 4  4  0.85 mm
SOT629-1
PCA9541ABS/03
41A3
HVQFN16
plastic thermal enhanced very thin quad flat package;
no leads; 16 terminals; body 4  4  0.85 mm
SOT629-1
4.1 Ordering options
Table 2.
Ordering options
Type number
Orderable
part number
Package
Packing method
PCA9541AD/01
PCA9541AD/01,112
SO16
Standard marking
1000
* IC’s tube - DSC bulk pack
Tamb = 40 C to +85 C
PCA9541AD/01,118
SO16
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9541AD/03,112
SO16
Standard marking
1000
* IC’s tube - DSC bulk pack
Tamb = 40 C to +85 C
PCA9541AD/03,118
SO16
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9541APW/01,112
TSSOP16
Standard marking
2400
* IC’s tube - DSC bulk pack
Tamb = 40 C to +85 C
PCA9541APW/01,118
TSSOP16
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9541APW/03,112
TSSOP16
Standard marking
2400
* IC’s tube - DSC bulk pack
Tamb = 40 C to +85 C
PCA9541APW/03,118
TSSOP16
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9541ABS/01
PCA9541ABS/01,118
HVQFN16
Reel 13” Q1/T1
*Standard mark SMD
6000
Tamb = 40 C to +85 C
PCA9541ABS/03
PCA9541ABS/03,118
HVQFN16
Reel 13” Q1/T1
*Standard mark SMD
6000
Tamb = 40 C to +85 C
PCA9541AD/03
PCA9541APW/01
PCA9541APW/03
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
Minimum Temperature
order
quantity
© NXP Semiconductors N.V. 2014. All rights reserved.
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
5. Block diagram
PCA9541A
SCL_MST0
SDA_MST0
INPUT
FILTER
A3
A2
A1
A0
RESET
VDD
SCL_MST1
SDA_MST1
STOP
DETECTION
BUS
SENSOR
SLAVE
CHANNEL
SWITCH
CONTROL
LOGIC
I2C-BUS
CONTROL
AND
REGISTER
BANK
SCL_SLAVE
SDA_SLAVE
POWER-ON
RESET
INPUT
FILTER
STOP
DETECTION
BUS
RECOVERY/
INITIALIZATION
OSCILLATOR
INT0
INT1
INTERRUPT
LOGIC
INT_IN
002aae656
VSS
Fig 1.
Block diagram of PCA9541A
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
6. Pinning information
6.1 Pinning
PCA9541AD/01
PCA9541AD/03
INT0
1
16 VDD
SDA_MST0
2
15 INT_IN
SCL_MST0
3
14 SDA_SLAVE
RESET
4
13 SCL_SLAVE
SCL_MST1
5
12 A3
SDA_MST1
6
11 A2
INT1
7
VSS
8
10 A1
9
INT0
1
16 VDD
SDA_MST0
2
15 INT_IN
SCL_MST0
3
RESET
4
SCL_MST1
5
SDA_MST1
6
11 A2
INT1
7
10 A1
VSS
8
A0
14 SDA_SLAVE
PCA9541APW/01
PCA9541APW/03
12 A3
9
A0
002aae658
002aae657
SDA_MST1
4
14 VDD
13 INT_IN
11 SCL_SLAVE
10 A3
9
8
3
A1
SCL_MST1
PCA9541ABS/01
PCA9541ABS/03
7
2
A0
RESET
Pin configuration for TSSOP16
12 SDA_SLAVE
6
1
VSS
SCL_MST0
5
terminal 1
index area
15 INT0
Fig 3.
16 SDA_MST0
Pin configuration for SO16
INT1
Fig 2.
13 SCL_SLAVE
A2
002aae659
Transparent top view
Fig 4.
Pin configuration for HVQFN16
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
6.2 Pin description
Table 3.
Pin description
Symbol
Pin
Description
SO16,
TSSOP16
HVQFN16
INT0
1
15
active LOW interrupt output 0 (external pull-up required)
SDA_MST0
2
16
serial data master 0 (external pull-up required)
SCL_MST0
3
1
serial clock master 0 (external pull-up required)
RESET
4
2
active LOW reset input (external pull-up required)
SCL_MST1
5
3
serial clock master 1 (external pull-up required)
SDA_MST1
6
4
serial data master 1 (external pull-up required)
INT1
7
5
active LOW interrupt output 1 (external pull-up required)
8
6[1]
supply ground
VSS
A0
9
7
address input 0 (externally held to VSS or VDD)
A1
10
8
address input 1 (externally held to VSS or VDD)
A2
11
9
address input 2 (externally held to VSS or VDD)
A3
12
10
address input 3 (externally held to VSS or VDD)
SCL_SLAVE
13
11
serial clock slave (external pull-up required)
SDA_SLAVE
14
12
serial data slave (external pull-up required)
INT_IN
15
13
active LOW interrupt input (external pull-up required)
VDD
16
14
supply voltage
[1]
HVQFN16 package die supply ground is connected to both the VSS pin and the exposed center pad. The
VSS pin must be connected to supply ground for proper device operation. For enhanced thermal, electrical,
and board-level performance, the exposed pad must be soldered to the board using a corresponding
thermal pad on the board, and for proper heat conduction through the board thermal vias must be
incorporated in the printed-circuit board in the thermal pad region.
7. Functional description
Refer to Figure 1 “Block diagram of PCA9541A”.
7.1 Device address
Following a START condition, the upstream master that wants to control the I2C-bus or
make a status check must send the address of the slave it is accessing. The slave
address of the PCA9541A is shown in Figure 5. To conserve power, no internal pull-up
resistors are incorporated on the hardware selectable pins and they must be pulled HIGH
or LOW.
1
1
1
A3
fixed
A2
A1
A0 R/W
hardware
selectable
002aab390
Fig 5.
PCA9541A
Product data sheet
Slave address
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
The last bit of the slave address defines the operation to be performed. When set to
logic 1 a read is selected, while logic 0 selects a write operation.
Remark: Reserved I2C-bus addresses must be used with caution since they can interfere
with:
• ‘reserved for future use’ I2C-bus addresses (1111 1XX)
• slave devices that use the 10-bit addressing scheme (1111 0XX)
7.2 Command Code
Following the successful acknowledgement of the slave address, the bus master sends a
byte to the PCA9541A, which is stored in the Command Code register.
0
0
0
AI
0
auto-increment
0
B1
B0
register number
002aab391
Fig 6.
Command Code
The 2 LSBs are used as a pointer to determine which register is accessed.
If the auto-increment flag is set (AI = 1), the two least significant bits of the Command
Code are automatically incremented after a byte has been read or written. This allows the
user to program the registers sequentially or to read them sequentially.
• During a read operation, the contents of these bits will roll over to 00b after the last
allowed register is accessed (10b).
• During a write operation, the PCA9541A acknowledges bytes sent to the IE and
CONTROL registers, but does not acknowledge a byte sent to the Interrupt Status
Register since it is a read-only register. The 2 LSBs of the Command Code do not roll
over to 00b but stay at 10b.
Only the 2 least significant bits are affected by the AI flag.
Unused bits must be programmed with zeros. Any command code (write operation)
different from ‘000AI 0000’, ‘000AI 0001’, and ‘000AI 0010’ are not acknowledged. At
power-up, this register defaults to all zeros.
Table 4.
Command Code register
B1
B0
Register name
Type
Register function
0
0
IE
R/W
interrupt enable
0
1
CONTROL
R/W
control switch
1
0
ISTAT
R only
interrupt status
1
1
not allowed
Each system master controls its own set of registers, however they can also read specific
bits from the other system master.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
PCA9541A
IE
REG#00
IE 0
IE 1
REG#00
IE
CONTROL
REG#01
CONTROL 0
CONTROL 1
REG#01
CONTROL
ISTAT
REG#10
ISTAT 0
ISTAT 1
REG#10
ISTAT
MASTER 0
SCL_MST0
SDA_MST0
Fig 7.
002aae660
MASTER 1
SCL_MST1
SDA_MST1
Internal register map
7.3 Interrupt Enable and Control registers description
When a master seeks control of the bus by connecting its I2C-bus channel to the
PCA9541A downstream channel, it has to write to the CONTROL register (Reg#01).
Bits MYBUS and BUSON allow the master to take control of the bus.
The MYBUS and the NMYBUS bits determine which master has control of the bus.
Table 9 explains which master gets control of the bus and how. There is no arbitration.
Any master can take control of the bus when it wants regardless of whether the other
master is using it or not.
The BUSON and the NBUSON bits determine whether the upstream bus is connected or
disconnected to/from the downstream bus. Table 10 explains when the upstream bus is
connected or disconnected.
Internally, the state machine does the following:
• If the combination of the BUSON and the NBUSON bits causes the upstream to be
disconnected from the downstream bus, then that is done. So in this case, the values
of the MYBUS and the NMYBUS do not matter.
• If a master was connected to the downstream bus prior to the disconnect, then an
interrupt is sent on the respective interrupt output in an attempt to let that master know
that it is no longer connected to the downstream bus. This is indicated by setting the
BUSLOST bit in the Interrupt Status Register.
• If the combination of the BUSON and the NBUSON bits causes a master to be
connected to the downstream bus and if there is no change in the BUSON bits since
when the disconnect took effect, then the master requesting the bus is connected to
the downstream bus. If it requests a bus initialization sequence, then it is performed.
• If there is no change in the combination of the BUSON and the NBUSON bits and a
new master wants the bus, then the downstream bus is disconnected from the old
master that was using it and the new master gets control of it. Again, the bus
initialization if requested is done. The appropriate interrupt signals are generated.
After a master has sent the bus control request:
1. The previous master is disconnected from the I2C-bus. An interrupt to the previous
master is sent through its INT line to let it know that it lost control of the bus.
BUSLOST bit in the Interrupt Status Register is set. This interrupt can be masked by
setting the BUSLOSTMSK bit to logic 1.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
2. A built-in bus initialization/recovery function can take temporary control of the
downstream channel to initialize the bus before making the actual switch to the new
bus master. This function is activated by setting the BUSINIT to logic 1 by the master
during the same write sequence as the one programming MYBUS and BUSON bits.
When activated and whether the bus was previously idle or not:
a. 9 clock pulses are sent on the SCL_SLAVE.
b. SDA_SLAVE line is released (HIGH) when the clock pulses are sent to
SCL_SLAVE. This is equivalent to sending 8 data bits and a not acknowledge.
c. Finally a STOP condition is sent to the downstream slave channel.
This sequence completes any read transaction which was previously in process and
the downstream slave configured as a slave-transmitter should release the SDA line
because the PCA9541A did not acknowledge the last byte.
3. When the initialization has been requested and completed, the PCA9541A sends an
interrupt to the new master through its INT line and connects the new master to the
downstream channel. BUSINIT bit in the Interrupt Status Register is set. The switch
operation occurs after the master asking the bus control has sent a STOP
command. This interrupt can be masked by setting the BUSINITMSK bit to logic 1.
4. When the bus initialization/recovery function has not been requested (BUSINIT = 0),
the PCA9541A connects the new master to the slave downstream channel. The
switch operation occurs after the master asking the bus control has sent a
STOP command. If the built-in bus sensor function detects a non-idle condition in the
downstream slave channel at the switching time, PCA9541A sends an interrupt to the
new master through its INT line. BUSOK bit in the Interrupt Status Register is set. This
means that a STOP condition has not been detected in the previous bus
communication and that an external bus recovery/initialization must be performed. If
an idle condition has been detected at the switching time, no interrupt is sent. This
interrupt can be masked by setting the BUSOKMSK bit to logic 1.
Interrupt status can be read. See Section 7.4 “Interrupt Status registers” for more
information.
The MYTEST and the NMYTEST bits cause the interrupt pins of the respective masters to
be activated for a ‘functional interrupt test’.
Remark: The regular way to proceed is that a master asks to take the control of the bus
by programming MYBUS and BUSON bits based on NMUYBUS and NBUSON values.
Nevertheless, the same master can also decide to give up the control of the bus and give
it to the other master. This is also done by programming the MYBUS and BUSON bits
based on NMYBUS and NBUSON values.
Remark: Any writes either to the Interrupt Enable Register or the Control Register cause
the respective register to be updated on the ninth clock cycle, that is, on the rising edge of
the acknowledge clock cycle.
Remark: The actual switch from one channel to another or the switching off of both the
channels happens on a STOP command that is sent by the master requesting the switch.
PCA9541A
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
7.3.1 Register 0: Interrupt Enable (IE) register (B1:B0 = 00b)
This register allows a master to read and/or write (if needed) Mask options for its own
channel.
The Interrupt Enable register described below is identical for both the masters.
Nevertheless, there are physically 2 internal Interrupt Enable registers, one for each
upstream channel. When Master 0 reads/writes in this register, the internal Interrupt
Enable Register 0 is accessed. When Master 1 reads/writes in this register, the internal
Interrupt Enable Register 1 is accessed.
Table 5.
Register 0 - Interrupt Enable (IE) register (B1:B0 = 00b) bit allocation
7
6
5
4
3
2
1
0
0
0
0
0
BUSLOSTMSK
BUSOKMSK
BUSINITMSK
INTINMSK
Table 6.
Register 0 - Interrupt Enable (IE) register bit description
Legend: * default value
Bit
Symbol
Access Value[1] Description
7:4
-
R only
0*
not used
3
BUSLOSTMSK
R/W
0*
An interrupt on INT will be generated after the other master has been
disconnected.
1
An interrupt on INT will not be generated after the other master has been
disconnected.
0*
After connection is requested and Bus Initialization not requested
(BUSINIT = 0), an interrupt on INT will be generated when a non-idle situation
has been detected on the downstream slave channel by the bus sensor at the
switching moment.
2
BUSOKMSK
R/W
Remark: Channel switching is done automatically after the STOP command.
1
After connection is requested and Bus Initialization not requested
(BUSINIT = 0), an interrupt on INT will not be generated when a non-idle
situation has been detected on the downstream slave channel by the bus
sensor at the switching moment (masked).
Remark: Channel switching is done automatically after the STOP command.
1
BUSINITMSK
R/W
0*
After connection is requested and Bus Initialization requested (BUSINIT = 1),
an interrupt on INT will be generated when the bus initialization is done.
Remark: Channel switching is done after bus initialization completed.
1
After connection is requested and Bus Initialization requested (BUSINIT = 1),
an interrupt on INT will not be generated when the bus initialization is done
(masked).
Remark: Channel switching is done after bus initialization completed.
0
[1]
INTINMSK
R/W
0*
Interrupt on INT_IN generates an interrupt on INT.
1
Interrupt on INT_IN does not generate an interrupt on INT (masked)
Default values are the same for PCA9541A/01, PCA9541A/03.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
7.3.2 Register 1: Control Register (B1:B0 = 01b)
The Control Register described below is identical for both the masters. Nevertheless,
there are physically 2 internal Control Registers, one for each upstream channel.
When master 0 reads/writes in this register, the internal Control Register 0 is accessed.
When master 1 reads/writes in this register, the internal Control Register 1 is accessed.
Table 7.
Register 1 - Control Register (B1:B0 = 01b) bit allocation
7
6
5
4
3
2
1
0
NTESTON
TESTON
0
BUSINIT
NBUSON
BUSON
NMYBUS
MYBUS
Table 8.
Register 1 - Control Register (B1:B0 = 01b) bit description
Legend: * default value
Bit
Symbol
Access Value[1]
Description
7
NTESTON
R/W
0*
A logic level HIGH to the INT line of the other channel is sent (interrupt
cleared).
1
A logic level LOW to the INT line of the other channel is sent (interrupt
generated).
0*
A logic level HIGH to the INT line is sent (interrupt cleared).
1
A logic level LOW to the INT line is sent (interrupt generated).
6
TESTON
R/W
5
-
R only
0*
not used
4
BUSINIT
R/W
0*
Bus initialization is not requested.
1
Bus initialization is requested.
3
NBUSON
R only
see Table 11
NBUSON bit along with BUSON bit decides whether any upstream channel
is connected to the downstream channel or not. See Table 10, Table 11, and
Table 12.
2
BUSON
R/W
see Table 11
BUSON bit along with the NBUSON bit decides whether any upstream
channel is connected to the downstream channel or not. See Table 10,
Table 11, and Table 12.
1
NMYBUS
R only
see Table 11
NMYBUS bit along with MYBUS bit decides which upstream channel is
connected to the downstream channel. See Table 9, Table 11, and Table 12.
0
MYBUS
R/W
see Table 11
MYBUS bit along with the NMYBUS bit decides which upstream channel is
connected to the downstream channel. See Table 9, Table 11, and Table 12.
[1]
Default values are the same for PCA9541A/01, PCA9541A/03.
Table 9.
MYBUS and NMYBUS truth table
As a master reads its Control Register
NMYBUS[1] MYBUS[1]
Slave channel
0
0
The master reading this combination has control of the bus.
1
0
The master reading this combination does not have control of the bus.
0
1
The master reading this combination does not have control of the bus.
1
1
The master reading this combination has control of the bus.
[1]
MYBUS and NMYBUS is an exclusive-OR type function where:
Equal values (00b or 11b) means that the master reading its Control Register has control of the bus.
Different values (01b or 10b) means that the master reading its Control Register does not have control of
the bus.
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2-to-1 I2C-bus master selector with interrupt logic and reset
Table 10.
BUSON and NBUSON truth table
NBUSON[1]
BUSON[1]
Slave channel
0
0
off
1
0
on
0
1
on
1
1
off
[1]
BUSON and NBUSON is an exclusive-OR type function where:
Equal values (00b or 11b) means that the connection between the upstream and the downstream channels
is off.
Different values (01b or 10b) means that the connection between the upstream and the downstream
channels is on.
Switch to the new channel is done when the master initiating the switch request sends a
STOP command to the PCA9541A.
If either master wants to change the connection of the downstream channel, it must write
to its Control Register (Reg#01), and then send a STOP command because an update
of the connection to the downstream according to the values in the two internal Control
Registers happens only on a STOP command. Writing to one control register followed by
a STOP condition on the other master's channel does not cause an update to the
downstream connection.
When both masters request a switch to their own channel at the same time, the master
who last wrote to its Control Register before the PCA9541A receives a STOP command
wins the switching sequence. There is no arbitration performed.
The Auto Increment feature (AI = 1) allows programming the PCA9541A in 4 bytes:
Start
111A3A2A1A0 + 0
00010000
Data Reg#00
Data Reg#01
Stop
Table 11.
PCA9541 Address + Write
Select Reg#00 with AI = 1
Interrupt Enable Register data
Control Register data
Default Control Register values
Type version
Master
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NTESTON
TESTON
not used
BUSINIT
NBUSON
BUSON
NMYBUS
MYBUS
PCA9541A/01 MST_0
0
0
0
0
0
1
0
0
MST_1
0
0
0
0
1
0
1
0
PCA9541A/03 MST_0
0
0
0
0
0
0
0
0
MST_1
0
0
0
0
0
0
1
0
Table 12 describes which command must be written to the Control Register when a
master device wants to take control of the I2C-bus. Byte written to the Control Register is
a function of the current I2C-bus control status performed after an initial reading of the
Control Register.
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
Current status of the I2C-bus is determined by the bits MYBUS, NMYBUS, BUSON and
NBUSON is one of the following:
•
•
•
•
The master reading its Control Register does not have control and the I2C-bus is off.
The master reading its Control Register does not have control and the I2C-bus is on.
The master reading its Control Register has control and the I2C-bus is off.
The master reading its Control Register has control and the I2C-bus is on.
‘I2C-bus off’ means that upstream and downstream channels are not connected together.
‘I2C-bus on’ means that upstream and downstream channels are connected together.
Remark: Only the 4 LSBs of the Control Register are described in Table 12 since only
those bits control the I2C-bus control. The logic value for the 4 MSBs is specific to the
application and are not discussed in the table.
The read sequence is performed by the master as:
S - 111xxxx0 - 000x0001 - Sr - 111xxxx1 - DataRead - P
The write sequence is performed by the master as:
S - 111xxxx0 - 000x0001 - DataWritten - P
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Bus control sequence
Read Control Register performed by the master
NBUSON BUSON
Write Control Register performed by the master
NMYBUS MYBUS
Byte
written[1][2]
(h)
Action performed
to take mastership
NBUSON[3] BUSON NMYBUS[3] MYBUS
Status
0
bus off
has control
0
0
0
0
4
bus on
x
1
x
0
1
bus off
no control
0
0
0
1
4
bus on, take control
x
1
x
0
2
bus off
no control
0
0
1
0
5
bus on, take control
x
1
x
1
3
bus off
has control
0
0
1
1
5
bus on
x
1
x
1
4
bus on
has control
0
1
0
0
-
no change
5
bus on
no control
0
1
0
1
4
take control
x
1
x
0
6
bus on
no control
0
1
1
0
5
take control
x
1
x
1
7
bus on
has control
0
1
1
1
-
no change
no write required
8
bus on
has control
1
0
0
0
-
no change
no write required
no write required
9
bus on
no control
1
0
0
1
0
take control
x
0
x
0
A
bus on
no control
1
0
1
0
1
take control
x
0
x
1
B
bus on
has control
1
0
1
1
-
no change
C
bus off
has control
1
1
0
0
0
bus on
x
0
x
0
D
bus off
no control
1
1
0
1
0
bus on, take control
x
0
x
0
E
bus off
no control
1
1
1
0
1
bus on, take control
x
0
x
1
F
bus off
has control
1
1
1
1
1
bus on
x
0
x
1
[1]
Only the 4 LSBs are shown.
[2]
x0x0 in binary = 0, 2, 8 or A in hexadecimal
x0x1 in binary = 1, 3, 9 or B in hexadecimal
x1x0 in binary = 4, 6, C or E in hexadecimal
PCA9541A
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x1x1 in binary = 5, 7, D or F in hexadecimal
x can be either ‘0’ or ‘1’ since those bits are read-only bits.
no write required
2-to-1 I2C-bus master selector with interrupt logic and reset
Rev. 5 — 24 April 2014
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Byte
read[1]
(h)
[3]
NXP Semiconductors
PCA9541A
Product data sheet
Table 12.
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
7.4 Interrupt Status registers
The PCA9541A provides 4 different types of interrupt:
• To indicate to the former I2C-bus master that it is not in control of the bus anymore
• To indicate to the new I2C-bus master that:
– The bus recovery/initialization has been performed and that the downstream
channel connection has been done (built-in bus recovery/initialization active).
– A ‘bus not well initialized’ condition has been detected by the PCA9541A when the
switch has been done (built-in bus recovery/initialization not active). This
information can be used by the new master to initiate its own bus
recovery/initialization sequence.
• Indicate to both I2C-bus upstream masters that a downstream interrupt has been
generated through the INT_IN pin.
• Functionality wiring test.
7.4.1 Bus control lost interrupt
When an upstream master takes control of the I2C-bus while the other channel was using
the downstream channel, an interrupt is generated to the master losing control of the bus
(INT line goes LOW to let the master know that it lost the control of the bus) immediately
after disconnection from the downstream channel.
By setting the BUSLOSTMSK bit to ‘1’, the interrupt is masked and the upstream master
that lost the I2C-bus control does not receive an interrupt (INT line does not go LOW).
7.4.2 Recovery/initialization interrupt
Before switching to a new upstream channel, an automatic bus recovery/initialization can
be performed by the PCA9541A. This function is requested by setting the BUSINIT bit to
‘1’. When the downstream bus has been initialized, an interrupt to the new master is
generated (INT line goes LOW).
By setting the BUSINITMSK bit to ‘1’, the interrupt is masked and the new master does
not receive an interrupt (INT line does not go LOW).
When the automatic bus recovery/initialization is not requested, if the built-in bus sensor
function (sensing permanently the downstream I2C-bus traffic) detects a non-idle
condition (previous bus channel connected to the downstream slave channel, was
between a START and STOP condition), then an interrupt to the new master is sent (INT
line goes LOW). This interrupt tells the new master that an external bus
recovery/initialization must be performed. By setting the BUSOKMSK bit to ‘1’, the
interrupt is masked and the new master does not receive an interrupt (INT line does not
go LOW).
Remark: In this particular situation, after the switch to the new master is performed,
a read of the Interrupt Status Register is not possible if the switch happened in the
middle of a read sequence because the new master does not have control of the SDA
line.
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
7.4.3 Downstream interrupt
An interrupt can also be generated by a downstream device by asserting the INT_IN pin
LOW. When INT_IN is asserted LOW, and if both INTINMSK bits are not set to ‘1’ by
either master, INT0 and INT1 both go LOW.
By setting the INTINMSK bit to ‘1’ by a master and/or the INTINMSK bit to ‘1’ by the other
master, the interrupts are masked and the corresponding masked channels do not receive
an interrupt (INT0 and/or INT1 line does not go LOW).
7.4.4 Functional test interrupt
A master can send an interrupt to itself to test its own INT wire or send an interrupt to the
other master to test its INT line. This is done by:
• setting the TESTON bit to ‘1’ to test its own INT line
• setting the NTESTON bit to ‘1’ to test the other master INT line
Setting the TESTON and/or NTESTON bits to ‘0’ by a master clears the interrupts.
Remark: Interrupt outputs have an open-drain structure. Interrupt input does not have any
internal pull-up resistor and must not be left floating (that is, pulled HIGH to VDD through
resistor) in order to avoid any undesired interrupt conditions.
7.4.5 Register 2: Interrupt Status Register (B1:B0 = 10b)
The Interrupt Status Register for both the masters is identical and is described below.
Nevertheless, there are physically 2 internal Interrupt Registers, one for each upstream
channel.
When Master 0 reads this register, the internal Interrupt Register 0 is accessed.
When Master 1 reads this register, the internal Interrupt Register 1 is accessed.
Table 13.
Register 2 - Interrupt Status register (B1:B0 = 10b) bit allocation
7
6
5
4
3
2
1
0
NMYTEST
MYTEST
0
0
BUSLOST
BUSOK
BUSINIT
INTIN
Table 14. Register 2 - Interrupt Status (ISTAT) register bit description
Legend: * default value
Bit
Symbol
Access Value[1] Description
7
NMYTEST[2]
R only
6
5
MYTEST[2]
R only
0*
no interrupt generated due to NTESTON bit from the other master
(NTESTON = 0 from the other master)[3]
1
interrupt generated due to TESTON bit from the other master
(NTESTON = 1 from the other master)[3]
0*
no interrupt generated by TESTON bit (TESTON = 0)[3]
1
interrupt generated by TESTON bit (TESTON = 1)[3]
-
R only
0*
not used
4
-
R only
0*
not used
3
BUSLOST[4]
R only
0*
no interrupt generated to the previous master when switching to the new one
is initiated
1
interrupt generated to the previous master when switching to the new one is
initiated
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2-to-1 I2C-bus master selector with interrupt logic and reset
Table 14. Register 2 - Interrupt Status (ISTAT) register bit description …continued
Legend: * default value
Bit
Symbol
Access Value[1] Description
2
BUSOK[4]
R only
BUSINIT[4]
1
INTIN[2]
0
R only
R only
0*
no interrupt generated by bus sensor function
1
interrupt generated by bus sensor function (masked when bus
recovery/initialization requested) - Bus was not idle when the switch occurred
0*
no interrupt generated by the bus recovery/initialization function
1
interrupt generated by the bus recovery/initialization function;
recovery/initialization done
0*
no interrupt on interrupt input (INT_IN)[5]
1
interrupt on interrupt input (INT_IN)[5]
[1]
Default values are the same for PCA9541A/01 and PCA9541A/03.
[2]
Reading the Interrupt Status Register does not clear the MYTEST, NMYTEST or the INTIN bits. They are cleared if:
INT_IN line goes HIGH for INTIN bit
TESTON bit is cleared for MYTEST bit
NTESTON bit is cleared for NMYTEST bit
[3]
Interrupt on a master is cleared after TESTON bit is cleared by the same master or NTESTON bit is cleared by the other master.
[4]
BUSINIT, BUSOK and BUSLOST bits in the Interrupt Status Register get cleared after a read of the same register is done. Precisely, the
register gets cleared on the second clock pulse during the read operation.
[5]
If the interrupt condition remains on INT_IN after the read sequence, another interrupt will be generated (if the interrupt has not been
masked).
7.5 Power-on reset
When power is applied to VDD, an internal power-on reset holds the PCA9541A in a reset
condition until VDD has reached VPOR. At this point, the reset condition is released and the
internal registers are initialized to their default states, with:
• PCA9541A/01: default Channel 0 (no STOP detect)
After power-up and/or insertion of the device in the main I2C-bus, the upstream
Channel 0 and the downstream slave channel are connected together.
• PCA9541A/03: default ‘no channel’ (no STOP detect)
After power-up and/or insertion of the device in the main I2C-bus, no channel will be
connected to the downstream channel. The device is ready to receive a START
condition and its address by a master.
If either register writes to its Control Register, then the connection between the
upstream and the downstream channels is determined by the values on the Control
Registers.
Thereafter, VDD must be lowered below 0.2 V for at least 5 s in order to reset the device.
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2-to-1 I2C-bus master selector with interrupt logic and reset
7.6 External reset
A reset can be accomplished by holding the RESET pin LOW for a minimum of tw(rst)L.
The PCA9541A registers and I2C-bus state machine are held in their default states until
the RESET input is once again HIGH. This input typically requires a pull-up resistor to
VDD.
Default states are:
• I2C-bus upstream Channel 0 connected to the I2C-bus downstream channel for the
PCA9541A/01
• no I2C-bus upstream channel connected to the I2C-bus downstream channel for the
PCA9541A/03.
7.7 Voltage translation
The pass gate transistors of the PCA9541A are constructed such that the VDD voltage can
be used to limit the maximum voltage that is passed from one I2C-bus to another.
002aaa964
5.0
Vo(sw)
(V)
4.0
(1)
(2)
3.0
(3)
2.0
1.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VDD (V)
(1) maximum
(2) typical
(3) minimum
Fig 8.
Pass gate voltage as a function of supply voltage
Figure 8 shows the voltage characteristics of the pass gate transistors (note that the graph
was generated using the data specified in Section 12 “Static characteristics” of this data
sheet). In order for the PCA9541A to act as a voltage translator, the Vo(sw) voltage should
be equal to, or lower than the lowest bus voltage. For example, if the main buses were
running at 5 V, and the downstream bus was 3.3 V, then Vo(sw) should be equal to or
below 3.3 V to effectively clamp the downstream bus voltages. Looking at Figure 8, we
see that Vo(sw)(max) is at 3.3 V when the PCA9541A supply voltage is 4.0 V or lower so the
PCA9541A supply voltage could be set to 3.3 V. Pull-up resistors can then be used to
bring the bus voltages to their appropriate levels (see Figure 17).
More Information on voltage translation can be found in Application Note AN262:
PCA954X family of I2C/SMBus multiplexers and switches.
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
8. Characteristics of the I2C-bus
The I2C-bus is for 2-way, 2-line communication between different ICs or modules. The two
lines are a serial data line (SDA) and a serial clock line (SCL). Both lines must be
connected to a positive supply via a pull-up resistor when connected to the output stages
of a device. Data transfer may be initiated only when the bus is not busy.
8.1 Bit transfer
One data bit is transferred during each clock pulse. The data on the SDA line must remain
stable during the HIGH period of the clock pulse as changes in the data line at this time
are interpreted as control signals (see Figure 9).
SDA
SCL
data line
stable;
data valid
Fig 9.
change
of data
allowed
mba607
Bit transfer
8.2 START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW
transition of the data line, while the clock is HIGH is defined as the START condition (S).
A LOW-to-HIGH transition of the data line while the clock is HIGH is defined as the
STOP condition (P) (see Figure 10).
SDA
SCL
S
P
START condition
STOP condition
mba608
Fig 10. Definition of START and STOP conditions
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2-to-1 I2C-bus master selector with interrupt logic and reset
8.3 System configuration
A device generating a message is a ‘transmitter’, a device receiving is the ‘receiver’. The
device that controls the message is the ‘master’ and the devices which are controlled by
the master are the ‘slaves’ (see Figure 11).
SDA
SCL
MASTER
TRANSMITTER/
RECEIVER
SLAVE
RECEIVER
SLAVE
TRANSMITTER/
RECEIVER
MASTER
TRANSMITTER
MASTER
TRANSMITTER/
RECEIVER
I2C-BUS
MULTIPLEXER
SLAVE
002aaa966
Fig 11. System configuration
8.4 Acknowledge
The number of data bytes transferred between the START and the STOP conditions from
transmitter to receiver is not limited. Each byte of 8 bits is followed by one acknowledge
bit. The acknowledge bit is a HIGH level put on the bus by the transmitter, whereas the
master generates an extra acknowledge related clock pulse.
A slave receiver which is addressed must generate an acknowledge after the reception of
each byte. Also a master must generate an acknowledge after the reception of each byte
that has been clocked out of the slave transmitter. The device that acknowledges has to
pull down the SDA line during the acknowledge clock pulse, so that the SDA line is stable
LOW during the HIGH period of the acknowledge related clock pulse; set-up and hold
times must be taken into account.
A master receiver must signal an end of data to the transmitter by not generating an
acknowledge on the last byte that has been clocked out of the slave. In this event, the
transmitter must leave the data line HIGH to enable the master to generate a STOP
condition.
data output
by transmitter
not acknowledge
data output
by receiver
acknowledge
SCL from master
1
2
S
START
condition
8
9
clock pulse for
acknowledgement
002aaa987
Fig 12. Acknowledgement on the I2C-bus
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
8.5 Bus transactions
slave address
data
Interrupt Enable (IE)
register
command code register
data control register
(CONTROL)
S 1 1 1 A3 A2 A1 A0 0 A 0 0 0 1 0 0 0 0 A
A
START condition
acknowledge
from slave
R/W
auto
increment
acknowledge
from slave
acknowledge
from slave
A P
acknowledge
from slave
STOP
condition
002aab607
Fig 13. Write to the Interrupt Enable and Control registers using the Auto-Increment (AI) bit
Remark: If a third data byte is sent, it is not acknowledged by the PCA9541A.
command code register
access to register
xx = 00, 01, or 10
slave address
S 1 1 1 A3 A2 A1 A0 0 A 0 0 0 1 0 0
START condition
R/W
auto
increment
acknowledge
from slave
(1)
x
slave address
x A Sr 1 1 1 A3 A2 A1 A0 1 A
acknowledge
from slave
re-START
condition
R/W
acknowledge
from slave
(3)
(2)
A
A
acknowledge
from master
acknowledge
from master
A P
no acknowledge
from master
STOP
condition
002aab608
(1) xx = 00: Interrupt Enable register
xx = 01: Control register
xx = 10: INT register
(2) xx = 00: Control register
xx = 01: INT register
xx = 10: Interrupt Enable register
(3) xx = 00: INT register
xx = 01: Interrupt Enable register
xx = 10: Control register
Fig 14. Read the 3 registers using the Auto-Increment (AI) bit
Remark: If a fourth data byte is read, the first register is accessed.
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command code register
NXP Semiconductors
PCA9541A
Product data sheet
SDA_MST0(1)
slave address
After the STOP condition
MASTER 1 is disconnected
from the downstream channel.
data Control register
S 1 1 1 A3 A2 A1 A0 0 A 0 0 0 AI 0 0 0 1 A 0 0 0 1 0 1 0 0 A P
START condition
R/W
acknowledge
from slave
auto
increment
acknowledge
from slave
BUSINIT
BUSON
MYBUS
acknowledge
from slave
INT1
if the interrupt is not masked
(BUSLOSTMSK = 0)
SCL_SLAVE
1 2 3 4 5 6 7 8 9
SDA_SLAVE
A
STOP command
INT0
if the interrupt is not masked
(BUSINITMSK = 0)
MASTER 1 has control of the bus
PCA9541 has control of the bus
MASTER 0
has control
of the bus
002aab609
(1) We assume that a read of the Control register was done by MASTER 0 before this sequence and that 000x 0101 was read (MASTER 1 controlling the bus).
Fig 15. Write to the Control register and switch from Channel 1 to Channel 0 (bus recovery/initialization requested)
PCA9541A
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MASTER 0 must wait for the 'bus free time' value
(between STOP and START) defined in the I2C-bus specification
before sending commands to the downstream devices.
2-to-1 I2C-bus master selector with interrupt logic and reset
Rev. 5 — 24 April 2014
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SCL_MST0
STOP
condition
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
SDA_MST0(1)
slave address
command code register
After the STOP condition MASTER 1
is disconnected from the downstream
channel, and MASTER 0 is connected to
the downstream channel.
data Control register
S 1 1 1 A3 A2 A1 A0 0 A 0 0 0 AI 0 0 0 1 A 0 0 0 0 0 1 0 0 A P
START condition
R/W
acknowledge
from slave
auto
increment
acknowledge
from slave
BUSINIT
BUSON
MYBUS
STOP
condition
acknowledge
from slave
SCL_MST0
INT1
if the interrupt is not masked
(BUSLOSTMSK = 0)
INT0
if MASTER 1 was not idle at the switching moment
and the interrupt is not masked (BUSINITMSK = 0)
MASTER 1 has control of the bus
MASTER 0 must wait for the 'bus free time' value
(between STOP and START) defined in the I2C-bus specification
before sending commands to the downstream devices.
MASTER 0 has control of the bus
002aab610
(1) We assume that a read of the Control register was done by MASTER 0 before this sequence and that 000x 0101 was read
(MASTER 1 controlling the bus).
Fig 16. Write to the Control register and switch from Channel 1 to Channel 0 (bus recovery/initialization not
requested)
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PCA9541A
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2-to-1 I2C-bus master selector with interrupt logic and reset
9. Application design-in information
SLAVE CARD
3.3 V
VDD
VDD
MASTER 0
SCL0
SCL_MST0
SDA0
SDA_MST0
RESET0
PCA9541A
INT0
INT0
SLAVE 2
INT
SDA
INT_IN
VSS
SCL
SDA_SLAVE
SCL_SLAVE
RESET
SDA SCL
SLAVE 1
SDA SCL
SLAVE 3
3.3 V
VDD
MASTER 1
SCL1
SCL_MST1
SDA1
SDA_MST1
RESET1
INT1
INT1
VSS
A3
A2
A1
A0
VSS
002aae661
Fig 17. Typical application
9.1 Specific applications
The PCA9541A is a 2-to-1 I2C-bus master selector designed for dual master, high
reliability I2C-bus applications, where continuous maintenance and control monitoring is
required even if one master fails or its controller card is removed for maintenance. The
PCA9541A can also be used in other applications, such as where masters share the
same resource but cannot share the same bus, as a gatekeeper multiplexer in long single
bus applications or as a bus initialization/recovery device.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
24 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
9.2 High reliability systems
SCL1
SDA1
MASTER 1
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
SCL0
SDA0
PCA9541A
MASTER 0
In a typical multipoint application, shown in Figure 18, the two masters (for example,
primary and back-up) are located on separate I2C-buses that connect to multiple
downstream I2C-bus slave cards/devices via a PCA9541A/01 for non-hot swap
applications to provide high reliability of the I2C-bus.
002aae662
Fig 18. High reliability backplane application
I2C-bus commands are sent via the primary or back-up master and either master can take
command of the I2C-bus. Either master at any time can gain control of the slave devices if
the other master is disabled or removed from the system. The failed master is isolated
from the system and does not affect communication between the on-line master and the
slave devices located on the cards.
SCL1
SDA1
MASTER 1
MASTER 1
MASTER 1
MASTER 1
SCL1
SDA1
PCA9541A
SCL0
SDA0
SCL1
SDA1
PCA9541A
MASTER 0
SCL0
SDA0
SCL1
SDA1
PCA9541A
MASTER 0
SCL0
SDA0
PCA9541A
MASTER 0
SCL0
SDA0
MASTER 0
For even higher reliability in multipoint backplane applications, two dedicated masters can
be used for every card as shown in Figure 19.
002aae663
Fig 19. Very high reliability backplane application
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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25 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
9.3 Masters with shared resources
Some masters may not be multi-master capable or some masters may not work well
together and continually lock up the bus. The PCA9541A can be used to separate the
masters, as shown in Figure 20, but still allow shared access to slave devices, such as
Field Replaceable Unit (FRU) EEPROMs or temperature sensors.
ASSEMBLY A
SDA/SCL
SLAVE A1
SLAVE A2
ASSEMBLY B
SDA/SCL
SLAVE B1
SLAVE B2
PCA9541A
MASTER A
SLAVE A0
MAIN
MASTER
PCA9541A
MASTER B
SLAVE B0
002aae664
Fig 20. Masters with shared resources application
9.4 Gatekeeper multiplexer
The PCA9541A/03 can act as a gatekeeper multiplexer in applications where there are
multiple I2C-bus devices with the same fixed address (for example, EEPROMs with
address of ‘Z’ as shown in Figure 21) connected in a multipoint arrangement to the same
I2C-bus. Up to 16 hot swappable cards/devices can be multiplexed to the same bus
master by using one PCA9541A/03 per card/device. Since each PCA9541A/03 has its
own unique address (for example, ‘A’, ‘B’, ‘C’, and so on), the EEPROMs can be
connected to the master, one at a time, by connecting one PCA9541A/03 (Master 0
position) while keeping the rest of the cards/devices isolated (off position).
The alternative, shown with dashed lines, is to use a PCA9548 1-to-8 channel switch on
the master card and run 8 I2C-bus devices, one to each EEPROM card, to multiplex the
master to each card. The number of card pins used is the same in either case, but there
are 7 fewer pairs of SDA/SCL traces on the printed-circuit board if the PCA9541A/03 is
used.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
26 of 45
PCA9541A
NXP Semiconductors
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
PCA9541A
A
B
C
D
E
F
G
H
EEPROM
EEPROM
EEPROM
EEPROM
EEPROM
EEPROM
EEPROM
EEPROM
PCA9548
MASTER 0
2-to-1 I2C-bus master selector with interrupt logic and reset
Z
Z
Z
Z
Z
Z
Z
Z
002aae665
Fig 21. Gatekeeper multiplexer application
9.5 Bus initialization/recovery to initialize slaves without hardware reset
If the I2C-bus is hung, I2C-bus devices without a hardware reset pin (for example, Slave 1
and Slave 2 in Figure 22) can be isolated from the master by the PCA9541A/03. The
PCA9541A/03 disconnects the bus when it is reset via the hardware reset line, restoring
the master's control of the rest of the bus (for example, Slave 0). The bus master can then
command the PCA9541A/03 to send 9 clock pulses/STOP condition to reset the
downstream I2C-bus devices before they are reconnected to the master or leave the
downstream devices isolated.
SDA/SCL
MASTER
SLAVE 1
PCA9541A/03
SDA
slave I2C-bus
SCL
SLAVE 0
SLAVE 2
RESET
002aae666
Fig 22. Bus initialization/recovery application
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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27 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
10. Limiting values
Table 15. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Voltages are referenced to VSS (ground = 0 V).[1]
Symbol
Parameter
Conditions
Min
Max
Unit
VDD
supply voltage
0.5
+7.0
V
VI
input voltage
0.5
+7.0
V
II
input current
20
+20
mA
IO
output current
25
+25
mA
IDD
supply current
100
+100
mA
ISS
ground supply current
100
+100
mA
Ptot
total power dissipation
-
400
mW
-
125
C
60
+150
C
40
+85
C
Tj(max)
maximum junction temperature
Tstg
storage temperature
Tamb
ambient temperature
[1]
[1]
operating in free air
The performance capability of a high-performance integrated circuit in conjunction with its thermal
environment can create junction temperatures which are detrimental to reliability. The maximum junction
temperature of this integrated circuit should not exceed 125 C.
11. Thermal characteristics
Table 16.
Thermal characteristics
Symbol
Parameter
Conditions
Typ
Unit
Rth(j-a)
thermal resistance from junction
to ambient
HVQFN16 package
40
C/W
SO16 package
115
C/W
TSSOP16 package
160
C/W
12. Static characteristics
Table 17. Static characteristics
VDD = 2.3 V to 5.5 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
2.3
-
5.5
V
VDD = 3.6 V
-
152
200
A
VDD = 5.5 V
-
349
600
A
-
30
80
A
-
40
100
A
-
1.5
2.1
V
Supply
VDD
supply voltage
IDD
supply current
Istb
standby current
Operating mode; no load;
VI = VDD or VSS; fSCL = 100 kHz
Standby mode; no load;
VI = VDD or VSS; fSCL = 0 kHz
VDD = 3.6 V
VDD = 5.5 V
VPOR
power-on reset voltage
PCA9541A
Product data sheet
no load; VI = VDD or VSS
[1]
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
28 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
Table 17. Static characteristics …continued
VDD = 2.3 V to 5.5 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
-
+0.3VDD
V
Input SCL_MSTn; input/output SDA_MSTn (upstream and downstream channels)
VIL
LOW-level input voltage
0.5
VIH
HIGH-level input voltage
0.7VDD
-
6
V
IOL
LOW-level output current VOL = 0.4 V
3
-
-
mA
VOL = 0.6 V
6
-
-
mA
1
-
+1
A
VDD = 2.3 V to 3.6 V
-
4
5
pF
VDD = 3.6 V to 5.5 V
-
4
6
pF
IL
leakage current
VI = VDD or VSS
Ci
input capacitance
VI = VSS
Select inputs A0 to A3, INT_IN, RESET
VIL
LOW-level input voltage
0.5
-
+0.3VDD
V
VIH
HIGH-level input voltage
0.7VDD
-
6
V
ILI
input leakage current
VI = VDD or VSS
1
-
+1
A
Ci
input capacitance
VI = VSS
VDD = 2.3 V to 3.6 V
-
2
3
pF
VDD = 3.6 V to 5.5 V
-
2
5
pF
VDD = 4.5 V to 5.5 V; VO = 0.4 V;
IO = 15 mA
4
12
24

VDD = 3.0 V to 3.6 V; VO = 0.4 V;
IO = 15 mA
5
14
30

VDD = 2.3 V to 2.7 V; VO = 0.4 V;
IO = 10 mA
7
17
55

Vi(sw) = VDD = 5.0 V; Io(sw) = 100 A
-
3.6
-
V
Vi(sw) = VDD = 4.5 V to 5.5 V;
Io(sw) = 100 A
2.6
-
4.5
V
Pass gate
ON-state resistance
Ron
Vo(sw)
switch output voltage
leakage current
IL
Vi(sw) = VDD = 3.3 V; Io(sw) = 100 A
-
2.2
-
V
Vi(sw) = VDD = 3.0 V to 3.6 V;
Io(sw) = 100 A
1.6
-
2.8
V
Vi(sw) = VDD = 2.5 V; Io(sw) = 100 A
-
1.5
-
V
Vi(sw) = VDD = 2.3 V to 2.7 V;
Io(sw) = 100 A
1.1
-
2.0
V
VI = VDD or VSS
1
-
+1
A
3
-
-
mA
INT0 and INT1 outputs
LOW-level output current VOL = 0.4 V
IOL
[1]
In order to reset the part, VDD must be lowered to 0.2 V for at least 5 s.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
13. Dynamic characteristics
Table 18.
Symbol
Dynamic characteristics
Parameter
Conditions
Standard-mode
I2C-bus
[1]
(SDA_MSTn to
SDA_SLAVE) or
(SCL_MSTn to
SCL_SLAVE)
Fast-mode
I2C-bus
Unit
Min
Max
Min
Max
-
0.3
-
0.3
tPD
propagation delay
fSCL
SCL clock frequency
0
100
0
400
kHz
fSCL(init/rec)
SCL clock frequency
(bus initialization/bus recovery)
50
150
50
150
kHz
tBUF
bus free time between a STOP and
START condition
4.7
-
1.3
-
s
tHD;STA
hold time (repeated) START condition
4.0
-
0.6
-
s
tLOW
LOW period of the SCL clock
4.7
-
1.3
-
s
tHIGH
HIGH period of the SCL clock
4.0
-
0.6
-
s
tSU;STA
set-up time for a repeated START
condition
4.7
-
0.6
-
s
tSU;STO
set-up time for STOP condition
4.0
-
0.6
-
s
tHD;DAT
data hold time
0[3]
3.45
0[3]
0.9
s
tSU;DAT
data set-up time
250
-
100
-
ns
tr
rise time of both SDA and SCL signals
-
1000
20 + 0.1Cb[4]
300
ns
[4]
300
ns
[2]
20 + 0.1Cb
ns
tf
fall time of both SDA and SCL signals
-
300
Cb
capacitive load for each bus line
-
400
-
400
pF
tSP
pulse width of spikes that must be
suppressed by the input filter
-
50
-
50
ns
tVD;DAT
data valid time
HIGH-to-LOW
[5]
-
1
-
1
s
LOW-to-HIGH
[5]
-
0.6
-
0.6
s
-
1
-
1
s
tv(INT_IN-INTn) valid time from pin INT_IN to pin INTn
signal
-
4
-
4
s
td(INT_IN-INTn) delay time from pin INT_IN to pin INTn
inactive
-
2
-
2
s
tVD;ACK
data valid acknowledge time
INT
tw(rej)L
LOW-level rejection time
INT_IN input
1
-
1
-
s
tw(rej)H
HIGH-level rejection time
INT_IN input
0.5
-
0.5
-
s
10
-
10
-
ns
500
-
500
-
ns
0
-
0
-
ns
RESET
tw(rst)L
LOW-level reset time
trst
reset time
tREC;STA
SDA clear
recovery time to START condition
[6][7]
[1]
Pass gate propagation delay is calculated from the 20  typical Ron and the 15 pF load capacitance.
[2]
After this period, the first clock pulse is generated.
[3]
A device must internally provide a hold time of at least 300 ns for the SDA signal (referred to the VIH(min) of the SCL signal) in order to
bridge the undefined region of the falling edge of SCL.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
30 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
[4]
Cb = total capacitance of one bus line in pF.
[5]
Measurements taken with 1 k pull-up resistor and 50 pF load.
[6]
Resetting the device while actively communicating on the bus may cause glitches or errant STOP conditions.
[7]
Upon reset, the full delay is the sum of trst and the RC time constant of the SDA bus.
0.7 × VDD
SDA
0.3 × VDD
tr
tBUF
tf
tHD;STA
tSP
tLOW
0.7 × VDD
SCL
0.3 × VDD
tHD;STA
P
tSU;STA
tHD;DAT
S
tHIGH
tSU;DAT
tSU;STO
Sr
P
002aaa986
Fig 23. Definition of timing on the I2C-bus
protocol
START
condition
(S)
tSU;STA
bit 7
MSB
(A7)
tLOW
bit 6
(A6)
tHIGH
bit 0
(R/W)
acknowledge
(A)
STOP
condition
(P)
1 / fSCL
0.7 × VDD
SCL
0.3 × VDD
tBUF
tf
tr
0.7 × VDD
SDA
0.3 × VDD
tSU;DAT
tHD;STA
tHD;DAT
tVD;DAT
tVD;ACK
tSU;STO
002aab175
Rise and fall times, refer to VIL and VIH.
Fig 24. I2C-bus timing diagram
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
ACK or read cycle
START
SCL
SDA
30 %
trst
RESET
50 %
50 %
tREC;STA
50 %
tw(rst)L
trst
50 %
INTn
002aae735
Fig 25. Definition of RESET timing
14. Test information
VDD
PULSE
GENERATOR
VI
RL
500 Ω
VO
6.0 V
open
VSS
DUT
RT
CL
50 pF
002aab393
Definitions test circuit:
RL = Load resistance.
CL = Load capacitance including jig and probe capacitance.
RT = Termination resistance should be equal to the output impedance Zo of the pulse generator.
Fig 26. Test circuitry for switching times
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
32 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
15. Package outline
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PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
33 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
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Fig 28. Package outline SOT403-1 (TSSOP16)
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
34 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
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Fig 29. Package outline SOT629-1 (HVQFN16)
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
16. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
16.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
16.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
•
•
•
•
•
•
Board specifications, including the board finish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Package placement
Inspection and repair
Lead-free soldering versus SnPb soldering
16.3 Wave soldering
Key characteristics in wave soldering are:
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
36 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
16.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 30) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 19 and 20
Table 19.
SnPb eutectic process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
 350
< 2.5
235
220
 2.5
220
220
Table 20.
Lead-free process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
350 to 2000
> 2000
< 1.6
260
260
260
1.6 to 2.5
260
250
245
> 2.5
250
245
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 30.
PCA9541A
Product data sheet
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Rev. 5 — 24 April 2014
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37 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
temperature
maximum peak temperature
= MSL limit, damage level
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 30. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
38 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
17. Soldering: PCB footprints
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Fig 31. PCB footprint for SOT109-1 (SO16); reflow soldering
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
39 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
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Fig 32. PCB footprint for SOT403-1 (TSSOP16); reflow soldering
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
40 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
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Fig 33. PCB footprint for SOT629-1 (HVQFN16); reflow soldering
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
41 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
18. Abbreviations
Table 21.
Abbreviations
Acronym
Description
AI
Auto Increment
CDM
Charged Device Model
DUT
Device Under Test
EEPROM
Electrically Erasable Programmable Read-Only Memory
ESD
ElectroStatic Discharge
FRU
Field Replaceable Unit
HBM
Human Body Model
I2C-bus
Inter-Integrated Circuit bus
IC
Integrated Circuit
POR
Power-On Reset
RC
Resistor-Capacitor network
SMBus
System Management Bus
19. Revision history
Table 22.
Revision history
Document ID
Release date
Data sheet status
Change notice
Supersedes
PCA9541A v.5
20140424
Product data sheet
-
PCA9541A v.4
Modifications:
•
•
•
•
Table 1 “Ordering information”: added “Topside marking” column
•
Section 7.7 “Voltage translation”, second paragraph, fourth sentence: corrected
from “when the PCA9541A supply voltage is 3.5 V or lower”
to “when the PCA9541A supply voltage is 4.0 V or lower”
(correction to documentation only; no change to device)
•
•
•
•
Table 15 “Limiting values”: added Tj(max) limits
Added Section 4.1 “Ordering options”
Deleted (old) Section 5, “Marking”
Section 7.5 “Power-on reset”, first paragraph, third sentence corrected from “VDD must be lowered
below 0.2 V to reset the device” to “VDD must be lowered below 0.2 V for at least 5 s in order to
reset the device” (correction to documentation only; no change to device)
Added Section 11 “Thermal characteristics”
Table 17 “Static characteristics”, Table note [1]: inserted phrase “for at least 5 s in order”
Added Section 17 “Soldering: PCB footprints”
PCA9541A v.4
20120824
Product data sheet
-
PCA9541A v.3
PCA9541A v.3
20090716
Product data sheet
-
PCA9541A v.2
PCA9541A v.2
20090604
Product data sheet
-
PCA9541A v.1
PCA9541A v.1
20090528
Objective data sheet
-
-
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
42 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
20. Legal information
20.1 Data sheet status
Document status[1][2]
Product status[3]
Definition
Objective [short] data sheet
Development
This document contains data from the objective specification for product development.
Preliminary [short] data sheet
Qualification
This document contains data from the preliminary specification.
Product [short] data sheet
Production
This document contains the product specification.
[1]
Please consult the most recently issued document before initiating or completing a design.
[2]
The term ‘short data sheet’ is explained in section “Definitions”.
[3]
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
20.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
Product specification — The information and data provided in a Product
data sheet shall define the specification of the product as agreed between
NXP Semiconductors and its customer, unless NXP Semiconductors and
customer have explicitly agreed otherwise in writing. In no event however,
shall an agreement be valid in which the NXP Semiconductors product is
deemed to offer functions and qualities beyond those described in the
Product data sheet.
20.3 Disclaimers
Limited warranty and liability — Information in this document is believed to
be accurate and reliable. However, NXP Semiconductors does not give any
representations or warranties, expressed or implied, as to the accuracy or
completeness of such information and shall have no liability for the
consequences of use of such information. NXP Semiconductors takes no
responsibility for the content in this document if provided by an information
source outside of NXP Semiconductors.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
PCA9541A
Product data sheet
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors and its suppliers accept no liability for
inclusion and/or use of NXP Semiconductors products in such equipment or
applications and therefore such inclusion and/or use is at the customer’s own
risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) will cause permanent
damage to the device. Limiting values are stress ratings only and (proper)
operation of the device at these or any other conditions above those given in
the Recommended operating conditions section (if present) or the
Characteristics sections of this document is not warranted. Constant or
repeated exposure to limiting values will permanently and irreversibly affect
the quality and reliability of the device.
Terms and conditions of commercial sale — NXP Semiconductors
products are sold subject to the general terms and conditions of commercial
sale, as published at http://www.nxp.com/profile/terms, unless otherwise
agreed in a valid written individual agreement. In case an individual
agreement is concluded only the terms and conditions of the respective
agreement shall apply. NXP Semiconductors hereby expressly objects to
applying the customer’s general terms and conditions with regard to the
purchase of NXP Semiconductors products by customer.
No offer to sell or license — Nothing in this document may be interpreted or
construed as an offer to sell products that is open for acceptance or the grant,
conveyance or implication of any license under any copyrights, patents or
other industrial or intellectual property rights.
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
43 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from competent authorities.
Non-automotive qualified products — Unless this data sheet expressly
states that this specific NXP Semiconductors product is automotive qualified,
the product is not suitable for automotive use. It is neither qualified nor tested
in accordance with automotive testing or application requirements. NXP
Semiconductors accepts no liability for inclusion and/or use of
non-automotive qualified products in automotive equipment or applications.
In the event that customer uses the product for design-in and use in
automotive applications to automotive specifications and standards, customer
(a) shall use the product without NXP Semiconductors’ warranty of the
product for such automotive applications, use and specifications, and (b)
whenever customer uses the product for automotive applications beyond
NXP Semiconductors’ specifications such use shall be solely at customer’s
own risk, and (c) customer fully indemnifies NXP Semiconductors for any
liability, damages or failed product claims resulting from customer design and
use of the product for automotive applications beyond NXP Semiconductors’
standard warranty and NXP Semiconductors’ product specifications.
Translations — A non-English (translated) version of a document is for
reference only. The English version shall prevail in case of any discrepancy
between the translated and English versions.
20.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
I2C-bus — logo is a trademark of NXP Semiconductors N.V.
21. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
PCA9541A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 24 April 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
44 of 45
PCA9541A
NXP Semiconductors
2-to-1 I2C-bus master selector with interrupt logic and reset
22. Contents
1
2
3
4
4.1
5
6
6.1
6.2
7
7.1
7.2
7.3
7.3.1
7.3.2
7.4
7.4.1
7.4.2
7.4.3
7.4.4
7.4.5
7.5
7.6
7.7
8
8.1
8.2
8.3
8.4
8.5
9
9.1
9.2
9.3
9.4
9.5
10
11
12
13
14
General description . . . . . . . . . . . . . . . . . . . . . . 1
Features and benefits . . . . . . . . . . . . . . . . . . . . 2
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ordering information . . . . . . . . . . . . . . . . . . . . . 3
Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 3
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pinning information . . . . . . . . . . . . . . . . . . . . . . 5
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 6
Functional description . . . . . . . . . . . . . . . . . . . 6
Device address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Command Code . . . . . . . . . . . . . . . . . . . . . . . . 7
Interrupt Enable and Control registers
description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Register 0: Interrupt Enable (IE) register
(B1:B0 = 00b) . . . . . . . . . . . . . . . . . . . . . . . . . 10
Register 1: Control Register (B1:B0 = 01b) . . 11
Interrupt Status registers. . . . . . . . . . . . . . . . . 15
Bus control lost interrupt . . . . . . . . . . . . . . . . . 15
Recovery/initialization interrupt. . . . . . . . . . . . 15
Downstream interrupt . . . . . . . . . . . . . . . . . . . 16
Functional test interrupt . . . . . . . . . . . . . . . . . 16
Register 2: Interrupt Status Register
(B1:B0 = 10b) . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power-on reset . . . . . . . . . . . . . . . . . . . . . . . . 17
External reset . . . . . . . . . . . . . . . . . . . . . . . . . 18
Voltage translation . . . . . . . . . . . . . . . . . . . . . 18
Characteristics of the I2C-bus . . . . . . . . . . . . 19
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
START and STOP conditions . . . . . . . . . . . . . 19
System configuration . . . . . . . . . . . . . . . . . . . 20
Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 20
Bus transactions . . . . . . . . . . . . . . . . . . . . . . . 21
Application design-in information . . . . . . . . . 24
Specific applications . . . . . . . . . . . . . . . . . . . . 24
High reliability systems . . . . . . . . . . . . . . . . . . 25
Masters with shared resources. . . . . . . . . . . . 26
Gatekeeper multiplexer . . . . . . . . . . . . . . . . . 26
Bus initialization/recovery to initialize slaves
without hardware reset . . . . . . . . . . . . . . . . . . 27
Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 28
Thermal characteristics . . . . . . . . . . . . . . . . . 28
Static characteristics. . . . . . . . . . . . . . . . . . . . 28
Dynamic characteristics . . . . . . . . . . . . . . . . . 30
Test information . . . . . . . . . . . . . . . . . . . . . . . . 32
15
16
16.1
16.2
16.3
16.4
17
18
19
20
20.1
20.2
20.3
20.4
21
22
Package outline. . . . . . . . . . . . . . . . . . . . . . . .
Soldering of SMD packages . . . . . . . . . . . . . .
Introduction to soldering. . . . . . . . . . . . . . . . .
Wave and reflow soldering. . . . . . . . . . . . . . .
Wave soldering . . . . . . . . . . . . . . . . . . . . . . .
Reflow soldering . . . . . . . . . . . . . . . . . . . . . .
Soldering: PCB footprints . . . . . . . . . . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . .
Legal information . . . . . . . . . . . . . . . . . . . . . .
Data sheet status . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information . . . . . . . . . . . . . . . . . . . .
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
36
36
36
36
37
39
42
42
43
43
43
43
44
44
45
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP Semiconductors N.V. 2014.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 24 April 2014
Document identifier: PCA9541A
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