General Description
The DS4520 is a 9-bit nonvolatile (NV) I/O expander with
64 bytes of NV user memory controlled by an I2C-
compatible serial interface. The DS4520 offers users a
digitally programmable alternative to hardware jumpers
and mechanical switches that are being used to control
digital logic nodes. Furthermore, the digital state of each
pin can be read through the serial interface. Each I/O
pin is independently configurable. The outputs are open
drain with selectable pullups. Each output has the ability
to sink up to 12mA. Since the device is NV, it powers up
in the desired state allowing it to control digital logic
inputs immediately on power-up without having to wait
for the host CPU to initiate control.
Applications
RAM-Based FPGA Bank Switching for
Multiple Profiles
Selecting Between Boot Flash
Setting ASIC Configurations/Profiles
Servers
Network Storage
Routers
Telecom Equipment
PC Peripherals
Features
♦Programmable Replacement for Mechanical
Jumpers and Switches
♦Nine NV Input/Output Pins
♦64-Byte NV User Memory (EEPROM)
♦I2C-Compatible Serial Interface
♦Up to 8 Devices Can be Multidropped on the
Same I2C Bus
♦Open-Drain Outputs with Configurable Pullups
♦Outputs Capable of Sinking 12mA
♦Low Power Consumption
♦Wide Operating Voltage (2.7V to 5.5V)
♦Operating Temperature Range: -40°C to +85°C
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
______________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
I/O_0 GND
I/O_8
I/O_7
I/O_6
I/O_5
A2
SCL
SDA
TOP VIEW
I/O_1
I/O_2
A0
I/O_3
I/O_4
A1
VCC
DS4520
Pin Configuration
SCL
I/O_0
I/O_1
I/O_2
I/O_3
I/O_4
I/O_5
I/O_6
I/O_7
I/O_8
SDA
A0
A1
A2
GND
FROM
SYSTEM
CONTROLLER
FPGA
CLOCK
GENERATOR
CPU
SPEED
SELECT
4.7kΩ4.7kΩ
0.1μF
VCC
VCC DS4520
Typical Operating Circuit
Rev 0; 6/04
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Add “/T&R” for tape and reel orders.
Ordering Information
PART TEMP RANGE PIN-PACKAGE
DS4520E -40°C to +85°C 16 TSSOP
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
2_____________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED DC OPERATING CONDITIONS
(TA= -40°C to +85°C)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage on VCC, SDA, and SCL Pins
Relative to Ground.............................................-0.5V to +6.0V
Voltage on A0, A1, A2, and I/O_n [n = 0 to 8]
Relative to Ground....-0.5V to (VCC + 0.5V) not to exceed +6.0V
Operating Temperature Range ...........................-40°C to +85°C
EEPROM Programming Temperature Range .........0°C to +70°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature ...See IPC/JEDEC J-STD-020A Specification
PARAMETER
SYMBOL
CONDITIONS MIN TYP MAX UNITS
Supply Voltage VCC (Note 1) +2.7 +5.5 V
Input Logic 1 VIH
0.7 x VCC VCC + 0.3
V
Input Logic 0 VIL -0.3
0.3 x VCC
V
DC ELECTRICAL CHARACTERISTICS
(VCC = +2.7V to +5.5V; TA= -40°C to +85°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS MIN TYP MAX UNITS
Standby Current ISTBY (Note 2) 2 10 µA
Input Leakage IL-1.0 +1.0 µA
Input Current each I/O Pin II/O 0.4V < VI/O < 0.9VCC (Note 3) -1.0 +1.0 µA
3mA sink current 0 0.4
Low-Level Output Voltage (SDA)
VOL SDA
6mA sink current 0 0.6 V
I/O Pin Low-Level Output Voltage
VOL I/O
12mA sink current 0.4 V
I/O Pin Pullup Resistors RPU 4.0 5.5 7.5 kΩ
I/O Capacitance CI/O (Note 4) 10 pF
Power-On Reset Voltage VPOR 1.6 V
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
_____________________________________________________________________ 3
Note 1: All voltages referenced to ground.
Note 2: ISTBY is specified with SDA = SCL = VCC, outputs floating, and inputs connected to VCC or GND.
Note 3: The DS4520 does not obstruct the SDA and SCL lines if VCC is switched off as long as the voltages applied to these inputs
do not violate their minimum and maximum input voltage levels.
Note 4: Guaranteed by design.
Note 5: Timing shown is for fast-mode (400kHz) operation. This device is also backward compatible with I2C standard-mode timing.
Note 6: CB—total capacitance of one bus line in picofarads.
Note 7: EEPROM write time applies to all the EEPROM memory and SRAM shadowed EEPROM memory when SEE = 0. The EEPROM
write time begins after a stop condition occurs.
AC ELECTRICAL CHARACTERISTICS (See Figure 2)
(VCC = +2.7V to +5.5V; TA= -40°C to +85°C, unless otherwise noted. Timing referenced to VIL(MAX) and VIH(MIN).)
PARAMETER
SYMBOL
CONDITIONS MIN TYP MAX UNITS
SCL Clock Frequency fSCL (Note 5) 0 400 kHz
Bus Free Time Between Stop and
Start Conditions tBUF 1.3 µs
Hold Time (Repeated) Start
Condition
tHD:STA
0.6 µs
Low Period of SCL tLOW 1.3 µs
High Period of SCL tHIGH 0.6 µs
Data Hold Time
tHD:DAT
0 0.9 µs
Data Setup Time
tSU:DAT
100 ns
Start Setup time
tSU:STA
0.6 µs
SDA and SCL Rise Time tR(Note 6) 20 + 0.1CB300 ns
SDA and SCL Fall Time tF(Note 6) 20 + 0.1CB300 ns
Stop Setup Time
tSU:STO
0.6 µs
SDA and SCL Capacitive Loading
CB(Note 6) 400 pF
EEPROM Write Time tWR (Note 7) 10 20 ms
NONVOLATILE MEMORY CHARACTERISTICS
(VCC = +2.7V to +5.5V, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS MIN TYP MAX UNITS
EEPROM Writes +70°C (Note 4)
50,000
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
4_____________________________________________________________________
Typical Operating Characteristics
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
DS4520 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
4.54.03.5
0.5
1.0
1.5
2.0
0
3.0 5.0
I/O0–I/O7 CONTROL BITS = 0
I/O0–I/O7 PULLUPS DISABLED
VCC = SDA = SCL
SUPPLY CURRENT vs. SCL FREQUENCY
DS4520 toc03
SCL FREQUENCY (kHz)
SUPPLY CURRENT (µA)
300200100
2
4
6
8
10
12
14
16
18
20
0
0400
VCC = SDA = 5V
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
_____________________________________________________________________ 5
Pin Description
PIN
NAME
FUNCTION
1I/O_0 Input/Output 0. Bidirectional I/O pin.
2I/O_1 Input/Output 1. Bidirectional I/O pin.
3I/O_2 Input/Output 2. Bidirectional I/O pin.
4I/O_3 Input/Output 3. Bidirectional I/O pin.
5I/O_4 Input/Output 4. Bidirectional I/O pin.
6A0I
2C Address Input. Inputs A0, A1, and A2 determine the I2C slave address of the device.
7A1I
2C Address Input. Inputs A0, A1, and A2 determine the I2C slave address of the device.
8V
CC Power-Supply Voltage
9SDA I2C Serial Data Open-Drain Input/Output
10 SCL I2C Serial Clock Input
11 A2 I2C Address Input. Inputs A0, A1, and A2 determine the I2C slave address of the device.
12 I/O_5 Input/Output 5. Bidirectional I/O pin.
13 I/O_6 Input/Output 6. Bidirectional I/O pin.
14 I/O_7 Input/Output 7. Bidirectional I/O pin.
15 I/O_8 Input/Output 8. Bidirectional I/O pin.
16 GND Ground
DS4520
I/O CONTROL
REGISTERS
I/O CELL (x9)
I/O_n
[n = 0 TO 8]
RPU
PULLUP ENABLE (F0h-F1h)
I/O CONTROL (F2h-F3h)
I/O STATUS (F8h-F9h)
I2C
INTERFACE
SDA
SCL
A0
A1
A2
GND
EEPROM
64 BYTES
USER MEMORY
[00h TO 3Fh]
VCC
VCC
VCC
Block Diagram
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
6_____________________________________________________________________
Detailed Description
The DS4520 contains nine bidirectional, NV, input/out-
put (I/O) pins, and a 64-byte EEPROM user memory.
The I/O pins and user memory are accessible through
an I2C-compatible serial bus.
Programmable NV I/O Pins
Each programmable I/O pin consists of an input and an
open-collector output with a selectable internal pullup
resistor. To enable the pullups for each I/O pin, write to
the Pullup Enable Registers (F0h and F1h). To pull the
output low or place the pulldown transistor into a high-
impedance state, write to the I/O Control Registers (F2h
and F3h). To read the voltage levels present on the I/O
pins, read the I/O Status Registers (F8h and F9h). To
determine the status of the output register, read the I/O
Control Registers and the Pullup Resistor Registers.
The I/O Control Registers and the Pullup Enable
Registers are all SRAM shadowed EEPROM registers. It
is possible to disable the EEPROM writes of the regis-
ters using the SEE bit in the Configuration Register.
This reduces the time required to write to the register
and increases the amount of times the I/O pins can be
adjusted before the EEPROM is worn out.
Memory Map and Memory Types
The DS4520 memory map is shown in Table 1. Three
different types of memory are present in the DS4520:
EEPROM, SRAM shadowed EEPROM, and SRAM.
Memory locations specified as EEPROM are NV.
Writing to these locations results in an EEPROM write
cycle for a time specified by tWR in the AC Electrical
Characteristics table. Locations specified as SRAM
shadowed EEPROM can be configured to operate in
one of two modes specified by the SEE bit (the LSB of
the Configuration Register, F4h). When the SEE bit = 0
(default), the memory location acts like EEPROM.
However, when SEE = 1, shadow SRAM is written to
instead of the EEPROM. This eliminates both the
EEPROM write time, tRW, as well as the concern of
wearing out the EEPROM. This is ideal for applications
that wish to constantly write to the I/Os. Power-up
default states can be programmed for the I/Os in
EEPROM (with SEE = 0) and then once powered-up,
SEE can be written to a 1 so the I/Os can be updated
periodically in SRAM. The final type of memory present
in the DS4520 is standard SRAM.
Slave Address and Address Pins
The DS4520’s slave address is determined by the state
of the A0, A1, and A2 address pins as shown in Figure 1.
Address pins connected to GND result in a ‘0’ in the cor-
responding bit position in the slave address. Conversely,
address pins connected to VCC result in a ‘1’ in the cor-
responding bit positions. I2C communication is
described in detail in a later section.
I2C Serial Interface Description
I2C Definitions
The following terminology is commonly used to
describe I2C data transfers.
Master Device: The master device controls the slave
devices on the bus. The master device generates SCL
clock pulses, start, and stop conditions.
Slave Devices: Slave devices send and receive data
at the master’s request.
Bus Idle or Not Busy: Time between stop and start
conditions when both SDA and SCL are inactive and in
their logic-high states. When the bus is idle it often initi-
ates a low-power mode for slave devices.
Start Condition: A start condition is generated by the
master to initiate a new data transfer with a slave.
Transitioning SDA from high to low while SCL remains
high generates a start condition. See the timing dia-
gram for applicable timing.
Stop Condition: A stop condition is generated by the
master to end a data transfer with a slave. Transitioning
SDA from low to high while SCL remains high gener-
ates a stop condition. See the timing diagram for
applicable timing.
Repeated Start Condition: The master can use a
repeated start condition at the end of one data transfer
to indicate that it immediately initiates a new data trans-
fer following the current one. Repeated starts are com-
monly used during read operations to identify a specific
memory address to begin a data transfer. A repeated
start condition is issued identically to a normal start
condition. See the timing diagram for applicable timing.
Bit Write: Transitions of SDA must occur during the low
state of SCL. The data on SDA must remain valid and
unchanged during the entire high pulse of SCL plus the
setup and hold time requirements (see Figure 2). Data is
shifted into the device during the rising edge of the SCL.
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
_____________________________________________________________________ 7
*THE SLAVE ADDRESS IS DETERMINED BY
ADDRESS PINS A0, A1, AND A2.
1
MSB
SLAVE
ADDRESS*
READ/WRITE
BIT
LSB
010
A2 A1 A0 R/W
Figure 1. DS4520 Slave Address Byte
Table 1. DS4520 Memory Map
ADDRESS
TYPE NAME FUNCTION
FACTORY
DEFAULT
00h to 3Fh
EEPROM User Memory
64 bytes of general-purpose user EEPROM. 00h
40 to E7h
—Reserved Undefined address space for future expansion. Reads and writes to this
space have no effect on the device. —
E8 to EFh
EEPROM
Reserved — —
F0h Pullup
Enable 0
Pullup enable for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Set
the corresponding bit to enable the pullup; clear the bit to disable the pullup.
00h
F1h Pullup
Enable 1
Pullup enable for I/O_8. I/O_8 is the LSB. Only the LSB is used. Set the LSB
bit to enable the pullup on I/O_8; clear the LSB to disable the pullup. 00h
F2h
I/O Control 0
I/O control for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Clearing
the corresponding bit of the register pulls the selected I/O pin low; setting the
bit places the pulldown transistor into a high-impedance state. When the
pulldown is high impedance, the output floats if no pullup/down is connected
to the pin.
FFh
F3h
I/O Control 1
I/O control for I/O_8. I/O_8 is the LSB. Only the LSB is used. Clearing the LSB
of the register pulls the I/O_8 pin low; setting the LSB places the pulldown
transistor into a high-impedance state. When the pulldown is high impedance,
the output floats if no pullup/down is connected to the pin.
01h
F4h
Configuration
Configuration register. The LSB is the SEE bit. When set, this bit disables
writes to the EEPROM; writing only affects the shadow SRAM. When set to 0,
both the EEPROM and the shadow SRAM is written.
00h
F5h to F7h
SRAM
Shadowed
EEPROM
[EEPROM
writes are
disabled if
the SEE
bit = 1]
User Memory
3 bytes of general-purpose user EEPROM. 00h
F8h
I/O Status 0
I/O status for I/O_0 to I/O_7. I/O_0 is the LSB and I/O_7 is the MSB. Writing to
this register has no effect. Read this register to determine the state of the
I/O_0 to I/O_7 pins.
F9h
I/O Status 1
I/O status for I/O_8. I/O_8 is the LSB. Only the LSB is used; the other bits
could be any value when read. Writing to this register has no effect. Read this
register to determine the state of the I/O_8 pin.
FAh to FFh
SRAM
SRAM User 6 bytes of general-purpose SRAM.
—
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
8_____________________________________________________________________
Bit Read: At the end a write operation, the master must
release the SDA bus line for the proper amount of setup
time before the next rising edge of SCL during a bit
read (see Figure 2). The device shifts out each bit of
data on SDA at the falling edge of the previous SCL
pulse and the data bit is valid at the rising edge of the
current SCL pulse. Remember that the master gener-
ates all SCL clock pulses including when it is reading
bits from the slave.
Acknowledgement (ACK and NACK): An acknowledge-
ment (ACK) or not acknowledge (NACK) is always the 9th
bit transmitted during a byte transfer. The device receiving
data (the master during a read or the slave during a write
operation) performs an ACK by transmitting a zero during
the 9th bit. A device performs a NACK by transmitting a
one during the 9th bit. Timing (Figure 2) for the ACK and
NACK is identical to all other bit writes. An ACK is the
acknowledgement that the device is properly receiving
data. A NACK is used to terminate a read sequence or as
an indication that the device is not receiving data.
Byte Write: A byte write consists of 8 bits of informa-
tion transferred from the master to the slave (most sig-
nificant bit first) plus a 1-bit acknowledgement from the
slave to the master. The 8 bits transmitted by the mas-
ter are done according to the bit write definition and the
acknowledgement is read using the bit read definition.
Byte Read: A byte read is an 8-bit information transfer
from the slave to the master plus a 1-bit ACK or NACK
from the master to the slave. The 8 bits of information
that are transferred (most significant bit first) from the
slave to the master are read by the master using the bit
read definition above, and the master transmits an ACK
using the bit write definition to receive additional data
bytes. The master must NACK the last byte read to ter-
minated communication so the slave returns control of
SDA to the master.
Slave Address Byte: Each slave on the I2C bus
responds to a slave address byte sent immediately fol-
lowing a start condition. The slave address byte con-
tains the slave address in the most significant 7 bits
and the R/Wbit in the least significant bit.
The DS4520’s slave address is determined by the state
of the A0, A1, and A2 address pins as shown in Figure
1. Address pins connected to GND result in a ‘0’ in the
corresponding bit position in the slave address.
Conversely, address pins connected to VCC result in a
‘1’ in the corresponding bit positions.
When the R/Wbit is 0 (such as in A0h), the master is
indicating it will write data to the slave. If R/W= 1, (A1h
in this case), the master is indicating it will read from
the slave.
SDA
SCL
tHD:STA
tLOW
tHIGH
tRtF
tBUF
tHD:DAT
tSU:DAT REPEATED
START
tSU:STA
tHD:STA
tSU:STO
tSP
STOP START
NOTE: TIMING IS REFERENCED TO VIL(MAX) AND VIH(MIN)
Figure 2. I2C Timing Diagram
If an incorrect slave address is written, the DS4520
assumes the master is communicating with another I2C
device and ignores the communication until the next
start condition is sent.
Memory Address: During an I2C write operation, the
master must transmit a memory address to identify the
memory location where the slave is to store the data.
The memory address is always the second byte trans-
mitted during a write operation following the slave
address byte.
I2C Communication
Writing a Single Byte to a Slave: The master must
generate a start condition, write the slave address byte
(R/W= 0), write the memory address, write the byte of
data, and generate a stop condition. Remember the
master must read the slave’s acknowledgement during
all byte write operations.
Writing Multiple Bytes to a Slave: To write multiple
bytes to a slave, the master generates a start condition,
writes the slave address byte (R/W= 0), writes the
memory address, writes up to 8 data bytes, and gener-
ates a stop condition.
The DS4520 is capable of writing up to 8 bytes (one
page or row) with a single write transaction. This is
internally controlled by an address counter that allows
data to be written to consecutive addresses without
transmitting a memory address before each data byte
is sent. The address counter limits the write to one 8-
byte page. Attempts to write to additional pages of
memory without sending a stop condition between
pages results in the address counter wrapping around
to the beginning of the present row. The first row
begins at address 00h and subsequent rows begin at
multiples of 8 there on (08h, 10h, 18h, 20h, etc).
To prevent address wrapping from occurring, the mas-
ter must send a stop condition at the end of the page,
and then wait for the bus free or EEPROM write time to
elapse. Then the master can generate a new start con-
dition, write the slave address byte (R/W= 0), and the
first memory address of the next memory row before
continuing to write data.
Acknowledge Polling: Any time an EEPROM page is
written, the DS4520 requires the EEPROM write time
(tW) after the stop condition to write the contents of the
page to EEPROM. During the EEPROM write time, the
device does not acknowledge its slave address
because it is busy. It is possible to take advantage of
this phenomenon by repeatedly addressing the
DS4520, which allows communication to continue as
soon as the device is ready. The alternative to acknowl-
edge polling is to wait for a maximum period of tWto
elapse before attempting to access the device.
EEPROM Write Cycles: When EEPROM writes occur,
the DS4520 writes the whole EEPROM memory page
even if only a single byte on a page was modified.
Writes that do not modify all 8 bytes on the page are
valid and do not corrupt any other bytes on the same
page. Because the whole page is written, even bytes
on the page that were not modified during the transac-
tion are still subject to a write cycle. The DS4520’s
EEPROM write cycles are specified in the Nonvolatile
Memory Characteristics table. The specification shown
is at the worst-case temperature. It is capable of han-
dling approximately 10x that many writes at room tem-
perature.
Reading a Single Byte from a Slave: Unlike the write
operation that uses the specified memory address byte
to define where the data is to be written, the read oper-
ation occurs at the present value of the memory
address counter. To read a single byte from the slave,
the master generates a start condition, writes the slave
address byte with R/W= 1, reads the data byte with a
NACK to indicate the end of the transfer, and generates
a stop condition. However, since requiring the master
to keep track of the memory address counter is imprac-
tical, the following method should be used to perform
reads from a specified memory location.
Manipulating the Address Counter for Reads: A
dummy write cycle can be used to force the address
counter to a particular value. To do this the master gen-
erates a start condition, writes the slave address byte
(R/W= 0), writes the memory address where it desires
to read, generates a repeated start condition, writes the
slave address byte (R/W= 1), reads data with ACK or
NACK as applicable, and generates a stop condition.
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
_____________________________________________________________________ 9
DS4520
9-Bit I2C Nonvolatile
I/O Expander Plus Memory
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
is a registered trademark of Dallas Semiconductor Corporation.
SLAVE
ADDRESS*
START
START
1 0 1 0 A2 A1 A0 R/W SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
MSB LSB MSB LSB MSB LSB
b7 b6 b5 b4 b3 b2 b1 b0
READ/
WRITE
REGISTER ADDRESS
b7 b6 b5 b4 b3 b2 b1 b0
DATA
STOP
SINGLE BYTE WRITE
-WRITE I/O CONTROL 0
REGISTER TO 00h
SINGLE BYTE WRITE
-WRITE PULLUP ENABLE 0
REGISTER TO FFh
SINGLE BYTE READ
-READ I/O STATUS 0 RESISTER
TWO BYTE WRITE
-WRITE I/O CONTROL 0 AND
I/O CONTROL 1 REGISTERS TO 00h
START STOP
10100000 11110 010
A0h F2h
START REPEATED
START
A1h
MASTER
NACK STOP
10100000 11111 000
F8h
10100 001
10100000 11110 010
A0h F2h
STOP
I/O STATUS
START 10100000 11110 000
A0h F0h
STOP
DATA
FFh
00h 00h
EXAMPLE I2C TRANSACTIONS (WHEN A0, A1, AND A2 ARE CONNECTED TO GND)
TYPICAL I2C WRITE TRANSACTION
*THE SLAVE ADDRESS IS DETERMINED BY ADDRESS PINS A0, A1, AND A2.
00000 000
11111 111
A0h
00000000
TWO BYTE READ
-READ I/O STATUS 0 AND I/O
STATUS 1 RGISTERS
A)
C)
B)
D)
D) START STOP
101000 00 111 11000
A0h F8h A1h
1010 0001 I/O STATUS 0
DATA
I/O STATUS 1
DATA
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
SLAVE
ACK
MASTER
ACK
MASTER
NACK
REPEATED
START
00000000
Figure 3. I2C Communication Examples
See Figure 3 for a read example using the repeated
start condition to specify the starting memory location.
Reading Multiple Bytes from a Slave: The read oper-
ation can be used to read multiple bytes with a single
transfer. When reading bytes from the slave, the master
simply ACKs the data byte if it desires to read another
byte before terminating the transaction. After the mas-
ter reads the last byte it must NACK to indicate the end
of the transfer and generates a stop condition.
Applications Information
Power-Supply Decoupling
To achieve best results, it is highly recommended that a
decoupling capacitor is used on the IC power-supply
pins. Typical values of decoupling capacitors are 0.01µF
and 0.1µF. Use a high-quality, ceramic, surface-mount
capacitor, and mount it as close as possible to the VCC
and GND pins of the IC to minimize lead inductance.
Chip Topology
TRANSISTOR COUNT: 14,398
SUBSTRATE CONNECTED TO GROUND
Package Information
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www.maxim-ic.com/DallasPackInfo.
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Maxim Integrated:
DS4520E+ DS4520E+TRL DS4520E