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PDF CPC5903 Data sheet ( Hoja de datos )
| Número de pieza | CPC5903 | |
| Descripción | Optically Isolated I2C Bus Repeater | |
| Fabricantes | IXYS | |
| Logotipo |  |
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INTEGRATED CIRCUITS DIVISION
CPC5903
Optically Isolated I2C Bus Repeater
Features
• Bidirectionally Buffers I2C SDA Signal
• Extends and Isolates I2C Interfaces
• Standard-mode and Fast-mode I2C
Side B Fast-mode Compatible VDDB > 4.5V
• Operates on 2.7V to 5.5V
• Voltage Level Translation
• Slew-Limited Drivers Reduce EMI
• Powerdown to Hi-Z Does Not Load I2C
• 3750Vrms Galvanic Isolation
• Single 8-pin Surface-Mount Package
Applications
• Isolated Control and Signal Monitoring
• Power-over-Ethernet
• Power Supply High Side Interface
• I2C Bus Length Extenders
• I2C Logic Level Translation
Approvals
• UL 1577 Certified Component: File E76270
• EN/IEC 60950 Certified Component:
TUV Certificate: B 11 10 49410 007
Pb e3
Description
The CPC5903 is a dual, optically isolated, logic-bus
repeater. It isolates two open-drain logic signals while
providing 3750Vrms of galvanic isolation. When the
two sides are powered by different supply voltages, it
also functions as a logic level translator for levels as
low as 2.7V or as high as 5.5V. Because the CPC5903
provides an isolated bidirectional buffer for the I2C
data signal and a unidirectional buffer for the I2C clock
signal, it is best suited for applications where clock
stretching is not required. This configuration also
requires the I2C bus master to be on the Side A bus.
Unlike transformer or capacitive isolators, optical
isolation passes DC signals and does not require
continuous clocking to ensure the proper state is
maintained. The CPC5903 always returns the buffered
signals to their proper state after transient
interruptions on either side.
Ordering Information
Part
CPC5903G
CPC5903GS
CPC5903GSTR
Description
8-Pin DIP (50 / Tube)
8-Pin Surface Mount (50 / Tube)
8-Pin Surface Mount (1000 / Reel)
Figure 1. CPC5903 Functional Block Diagram
VDDA
IA 1
VDDA
LED
B
GNDA 2
A
VDDA
IOA 3
VDDA
V
4 DDA
A
A
VDDA
LED
VDDB
LED
VDDB
D
Q
CLR
B
VDDB
8
VDDB
B
VDDB
7 OB
6
B
GNDB
VDDB
5 IOB
DS-CPC5903-R02
www.ixysic.com
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1 page  
INTEGRATED CIRCUITS DIVISION
CPC5903
1.8 Switching Specifications
Parameter
Conditions
Symbol Min Typ Max Units
I2C Clock Frequency
IIOA=6mA,
CLOADA=400pF
IOB=IIOB=3mA, CLOADB=200pF
IOB=IIOB=6mA, CLOADB=400pF,
VDDB 4.5V
fMAX
500
-
- kHz
Propagation Delay A to B 1
Falling
Rising
Propagation Delay IOB to IOA
Falling
Rising
VDDA=VDDB=3.3V,
RPUA=475,
RPUB=825
CI_A=CI_B=20pF
0.5VDDA to 0.5VDDB
0.2VDDB to 0.5VDDA
tPHL_AB
tPLH_AB
tPHL_BA
tPLH_BA
-
-
-
-
60 135
122 270
ns
90 170
165 275
ns
Propagation Delay IOB to IOA to IOB
Rising
0.2VDDB to 0.5VDDB
tPLH_BAB -
290 480 ns
1 Refer to “Side A to Side B Switching Waveforms” on page 6
2 Refer to “IOB to IOA Switching Waveforms” on page 6
R02 www.ixysic.com
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INTEGRATED CIRCUITS DIVISION
4 Design Considerations
The minimum value of the pull-up resistor, RPU, on the
I2C bus is chosen based upon the expected VDD
supply voltage range and the weakest load current
sinking device on the bus. Note: Systems that do not
need maximum bandwidth and busses with lower
capacitive loading can use a higher value for the
pull-up resistor to reduce power consumption.
4.1 Side A Pull-Up Resistors: RPUA
The weakest I2C compliant device on the Side A bus,
with RPUA to VDDA, must be able to pull the Side A
inputs below 0.4V for outputs rated at 3mA or 0.6V for
outputs rated at 6mA when VDDA is at its maximum.
For example, if the weakest device is only guaranteed
to sink 3mA then the maximum allowed logic low
output voltage will be 0.4V. For designs with
VDDA_max = 3.6V, the minimum voltage across the
pull-up resistor is:
Minimum RPUA Voltage = 3.6 - 0.4 = 3.2V
For the I2C minimum current sink requirement of 3mA,
the minimum value of the pull-up resistor is easily
calculated as:
RPUA_min = 3.2V / 3mA = 1066.7
Chose a standard value resistor that will not violate
this minimum value over tolerance and temperature,
such as a 1.1k, 1% tolerance, 100ppm/C
temperature coefficient resistor.
If all the non-CPC5903 devices on the Side A bus are
Fast-mode compliant (400pF capacitive loading
capable) with the required 6mA current sink capability,
then the bus can be configured for Fast-mode.
Resistor selection for Fast-mode is similar to the
example given above but because the logic low output
level is greater (0.6V) then the voltage across the
pull-up resistor will be less. Calculation of the
compliant Fast-mode bus minimum pull-up resistor
value is given by:
RPUA_min = (3.6 - 0.6)V / 6mA = 500
The minimum E96 standard value 1% tolerance,
100ppm/C temperature coefficient resistor is 511.
CPC5903
4.2 Side B Pull-Up Resistors
Calculating the pull-up resistor for Side B is similar to
the process used for Side A but with some additional
considerations.
Before proceeding, it must be pointed out that Side B
of the CPC5903 is Fast-mode compliant with
VDDB 4.5V. This means the CPC5903 Side B
outputs are 6mA capable, allowing bus operation of
400kb/s with up to 400pF of capacitive loading. For
VDDB supply levels below 4.5V the CPC5903 outputs
are only rated for 3mA, but can be operated at
Fast-mode speeds of 400kb/s whenever the bus
capacitive loading CLOAD 200pF. Greater capacitive
loading of the Side B bus limits the CPC5903 to data
rates of 100kb/s.
First, it must be determined if the Side B bus will be
configured for 3mA or 6mA operation. This is done by
evaluating the external (non-CPC5903) devices on the
Side B bus and the operational capabilities of the
CPC5903. There are three possibilities:
1) One or more of the external devices is limited to
3mA of output current sink.
2) All of the external devices are rated at 6mA of
output current sink and the Side B minimum supply
voltage VDDB 4.5V.
3) All of the external devices are rated at 6mA of
output current sink and the Side B minimum supply
voltage VDDB 4.5V.
For conditions 1 and 2 above the bus must be
configured for 3mA. Condition 3 is the only situation
where the bus can be configured for 6mA, a
Fast-mode requirement when capacitive bus loading is
an issue.
4.2.1 OB Pull-Up resistor: RPU-OB
Selecting the pull-up resistor for the OB bus is based
upon the manner in which the bus is expected to
operate within the restrictions listed above. Although
the additional design considerations discussed below
for selecting the IOB pull-up resistor, RPUB , are not
applicable to the OB pull-up resistor, the Side B
pull-up resistors should have the same value to
minimize skew between the clock and data. Therefore,
setting RPU-OB = RPUB is recommended.
R02 www.ixysic.com
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