General Description Features

General Description Features

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

General Description

The MAX7321 2-wire serial-interfaced peripheral features eight open-drain I/O ports with selectable internal pullups and transition detection. Any port may be used as a logic input or an open-drain output. Ports are overvoltage protected to +6V independent of supply voltage.

All I/O ports configured as inputs are continuously monitored for state changes (transition detection). State changes are indicated by the open-drain INT output.

The interrupt is latched, allowing detection of transient changes. When the MAX7321 is subsequently accessed through the serial interface, any pending interrupt is cleared.

The open-drain outputs are rated to sink 20mA and are capable of driving LEDs.

The RST input clears the serial interface, terminating any

I

2

C communication to or from the MAX7321.

The MAX7321 uses two address inputs with four-level logic to allow 16 I

2

C slave addresses. The slave address also determines the power-up logic state for the I/O ports, and enables or disables internal 40kΩ pullups in groups of four ports.

The MAX7321 is one device in a family of pin-compatible port expanders with a choice of input ports, open-drain

I/O ports, and push-pull output ports (see Table 1).

The MAX7321 is available in 16-pin QSOP and TQFN packages, and is specified over the automotive temper- ature range (-40°C to +125°C).

Applications

● Cell Phones

● SAN/NAS

● Servers

● Notebooks

● Satellite Radio

Pin Configurations

+

AD0

4

3

5

7

6

8

2

1

RST

AD2

P0

P1

P2

P3

GND

MAX7321

16

15

V+

SDA

14

13

SCL

INT

12 P7

11

10

9

P6

P5

P4

QSOP

Features

● 400kHz I

2

C Serial Interface

● +1.71V to +5.5V Operating Voltage

● 8 Open-Drain I/O Ports Rated to 20mA Sink Current

● I/O Ports Are Overvoltage Protected to +6V

● Any Port Can Be a Logic Input or an Open-Drain

Output

● Selectable I/O Port Power-Up Default Logic States

● Transient Changes Are Latched, Allowing Detection

Between Read Operations

● INT Output Alerts Change on Inputs

● AD0 and AD2 Inputs Select from 16 Slave

Addresses

● Low 0.6µA (typ) Standby Current

● -40°C to +125°C Operating Temperature

Ordering Information

PART TEMP RANGE

PIN-

PACKAGE

MAX7321AEE+ -40°C to +125°C 16 QSOP

MAX7321ATE+ -40°C to +125°C 16 TQFN-EP*

TOP

MARK

ADC

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Selector Guide

PART INPUTS

INTERRUPT

MASK

MAX7319

MAX7320

MAX7321 Up to 8

MAX7322

8

4

MAX7323 Up to 4

MAX7328 Up to 8

MAX7329 Up to 8

Yes

Yes

OPEN-

DRAIN

OUTPUTS

Up to 8

Up to 4

Up to 8

Up to 8

PUSH-PULL

OUTPUTS

8

4

4

Pin Configurations are continued at end of data sheet.

Typical Application Circuit and Functional Diagram appear at end of data sheet.

19-3738; Rev 4; 7/14

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Absolute Maximum Ratings

(All voltages referenced to GND.)

Supply Voltage V+ ...................................................-0.3V to +6V

SCL, SDA, AD0, AD2, RST,

INT

, P0–P7 ...............-0.3V to +6V

P0–P7 Sink Current ....................................................... 25mA

SDA Sink Current .............................................................. 10mA

INT Sink Current.................................................................10mA

Total V+ Current .................................................................50mA

Total GND Current ...........................................................100mA

I

SINK

= 6mA

Continuous Power Dissipation (T

A

= +70°C)

16-Pin QSOP (derate 8.3mW/°C above +70°C)..........667mW

16-Pin TQFN (derate 15.6mW/°C above +70°C) ......1250mW

Operating Temperature Range ......................... -40°C to +125°C

Junction Temperature ......................................................+150°C

Storage Temperature Range ............................ -65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Soldering Temperature (reflow)

QSOP ..........................................................................+240°C

TQFN ...........................................................................+260°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.

Electrical Characteristics

A A

= +25°C.) (Note 1)

PARAMETER

Operating Supply Voltage

Power-On Reset Voltage

Standby Current

(Interface Idle)

Supply Current

(Interface Running)

Input High Voltage

SDA, SCL, AD0, AD2, RST, P0–P7

Input Low Voltage

SDA, SCL, AD0, AD2, RST, P0–P7

Input Leakage Current

SDA, SCL, AD0, AD2, RST, P0–P7

Input Capacitance

SDA, SCL, AD0, AD2, RST, P0–P7

SYMBOL

V

+

V

POR

I

STB

I

+

V

IH

V

IL

I

IH

, I

IL

V+ falling

CONDITIONS

SCL and SDA and other digital inputs at V+ f

SCL

= 400kHz; other digital inputs at V+

V+ < 1.8V

V+ ≥ 1.8

V+ < 1.8V

V+ ≥ 1.8V

SDA, SCL, AD0, AD2, RST, P0–P7 at V+ or

GND, internal pullup disabled

MIN

1.71

0.8 x V+

0.7 x V+

-0.2

TYP

0.6

23

10

MAX UNITS

5.50

V

1.6

V

1.5

55

0.2 x V+

0.3 x V+

+0.2

µA

µA

V

V

µA pF

Output Low Voltage P0–P7 V

OL

V+ = +1.71V, I

SINK

= 5mA

V+ = +2.5V, I

SINK

= 10mA

V+ = +3.3V, I

SINK

= 15mA

V+ = +5V, I

SINK

= 20mA

90

110

130

140

180

210

230

250 mV

Output Low Voltage SDA V

OLSDA

250 mV

Output Low Voltage INT

Port Input Pullup Resistor

V

OLINT

R

PU

I

SINK

= 5mA

25

130

40

250

55 mV kΩ www.maximintegrated.com

Maxim Integrated │

2

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Port and Interrupt INT Timing Characteristics

(V+ = +1.71V to +5.5V, T

A

= -40°C to +125°C, unless otherwise noted. Typical values are at V+ = +3.3V, T

A

= +25°C.) (Note 1)

PARAMETER

Port Output Data Valid

Port Input Setup Time

Port Input Hold Time

INT Input Data Valid Time

INT Reset Delay Time from STOP

INT Reset Delay Time from

Acknowledge

SYMBOL

t

PPV t

PSU t

PH t

IV t

IP t

IR

C

L

≤ 100pF

C

L

≤ 100pF

C

L

≤ 100pF

CL

≤ 100pF

C

L

≤ 100pF

C

L

≤ 100pF

CONDITIONS MIN

0

4

TYP MAX

4

4

4

4

UNITS

µs

µs

µs

µs

µs

µs

Timing Characteristics

(V+ = +1.71V to +5.5V, T

A

= -40°C to +125°C, unless otherwise noted. Typical values are at V+ = +3.3V, T

A

= +25°C.) (Note 1)

PARAMETER

Serial-Clock Frequency

Bus Free Time Between a STOP and a START Condition

SYMBOL

f

SCL t

BUF

CONDITIONS MIN

1.3

TYP MAX

400

UNITS

kHz

µs

Hold Time (Repeated) START

Condition

Repeated START Condition Setup

Time

STOP Condition Setup Time

Data Hold Time

Data Setup Time

SCL Clock Low Period

SCL Clock High Period

Rise Time of Both SDA and SCL

Signals, Receiving

Fall Time of Both SDA and SCL

Signals, Receiving

Fall Time of SDA, Transmitting t

HD, STA t

SU, STA t

SU, STO t

HD, DAT t

SU, DAT t

LOW t

HIGH t

R t

F t

F,TX t

SP

(Note 2)

(Notes 3, 4)

(Notes 3, 4)

(Notes 3, 4)

(Note 5)

0.6

0.6

0.6

100

1.3

0.7

20 +

0.1C

b

20 +

0.1C

b

20 +

0.1C

b

50

0.9

300

300

250

µs

µs ns ns ns ns Pulse Width of Spike Suppressed

Capacitive Load for Each Bus

Line

RST Pulse Width

RST Rising to START Condition

Setup Time

C b t

W t

RST

(Note 3)

500

1

400

µs

µs ns

µs

µs pF ns

µs

Note 1: All parameters tested at T

A

= +25°C. Specifications over temperature are guaranteed by design.

Note 2: A master device must provide a hold time of at least 300ns for the SDA signal (referred to V

IL

of the SCL signal) in order to bridge the undefined region of SCL’s falling edge.

Note 3: Guaranteed by design.

Note 4: C b

= total capacitance of one bus line in pF. I

SINK

≤ 6mA. t

R

and t

F

measured between 0.3 x V+ and 0.7 x V+.

Note 5: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.

www.maximintegrated.com

Maxim Integrated │

3

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Typical Operating Characteristics

(T

A

= +25°C, unless otherwise noted.)

STANDBY CURRENT vs. TEMPERATURE

2.0

1.8

1.6

1.4

1.2

1.0

f

SCL

= 0kHz

V+ = +5.0V

V+ = +2.5V

V+ = +3.3V

0.8

0.6

0.4

V+ = +1.71V

0.2

0

-40 -25 -10 5 20 35 50 65 80 95 110 125

TEMPERATURE ( °C)

60

SUPPLY CURRENT vs. TEMPERATURE

50 f

SCL

= 400kHz

V+ = +5.0V

40

30

V+ = +3.3V

20

V+ = +2.5V

10

V+ = +1.71V

0

-40 -25 -10 5 20 35 50 65 80 95 110 125

TEMPERATURE ( °C)

OUTPUT VOLTAGE LOW vs. TEMPERATURE

0.40

0.35

0.30

0.25

0.20

0.15

I

V+ = +3.3V

SINK

= 15mA

I

V+ = +2.5V

SINK

= 10mA

I

V+ = +5.0V

SINK

= 20mA

0.10

0.05

I

V+ = +1.71V

SINK

= 5mA

0

-40 -25 -10 5 20 35 50 65 80 95 110 125

TEMPERATURE (

°

C)

Pin Description

PIN

QSOP TQFN

1, 3 15, 1

2

4–7, 9–12

8

13

14

15

16

16

2–5, 7–10

6

11

12

13

14

— EP

NAME FUNCTION

AD0,

AD2

Address Inputs. Select device slave address with AD0 and AD2. Connect AD0 and

AD2 to either GND, V+, SCL, or SDA to give four logic combinations (see Table 3).

RST Reset Input, Active Low. Drive RST low to clear the 2-wire interface.

P0–P7 Input/output Ports. P0 to P7 are open-drain I/Os.

GND Ground

INT Interrupt Output. INT is an open-drain output.

SCL I

2

C-Compatible Serial-Clock Input

SDA I

2

C-Compatible Serial-Data I/O

V+

Positive Supply Voltage. Bypass V+ to GND with a ceramic capacitor of at least

0.047µF as close to the device as possible.

EP Exposed Pad. Connect exposed pad to GND.

www.maximintegrated.com

Maxim Integrated │

4

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Detailed Description

MAX7319–MAX7329 Family Comparison

The MAX7319–MAX7323 family consists of five pin- compatible, eight-port expanders. Each version is optimized for different applications. The MAX7328 and MAX7329 are industry standard parts.

The MAX7324–MAX7327 family consists of four pin- compatible, 16-port expanders that integrate the functions of the MAX7320 and one of either the MAX7319,

MAX7321, MAX7322, or MAX7323.

Functional Overview

The MAX7321 is a general-purpose port expander operating from a +1.71V to +5.5V supply that provides eight open-drain I/O ports. Each open-drain output is rated to sink 20mA, and the entire device is rated to sink 100mA into all ports combined. The outputs drive loads connected to supplies up to +5.5V, independent of the MAX7321’s supply voltage.

The MAX7321 is set to one of 16 I

2

C slave addresses

(0x60 to 0x6F) using the address select inputs AD0 and

AD2, and is accessed over an I

2

C serial interface up to 400kHz. The RST input clears the serial interface in

Table 1. MAX7319MAX7329 Family Comparison

PART

I

2

C

SLAVE

ADDRESS

8-PORT EXPANDERS

INPUTS

INPUT

INTERRUPT

MASK

OPEN-

DRAIN

OUTPUTS

PUSH-

PULL

OUTPUTS

APPLICATION

MAX7319 110xxxx

MAX7320 101xxxx

MAX7321 110xxxx Up to 8

MAX7322 110xxxx

8

4

Yes

Yes

Up to 8

8

4

Input-only versions:

8 input ports with programmable latching transition detection interrupt and selectable pullups.

Offers maximum versatility for automatic input monitoring. An interrupt mask selects which inputs cause an interrupt on transitions, and transition flags identify which inputs have changed (even momentarily) since the ports were last read.

Output-only versions:

8 push-pull outputs with selectable power-up default levels.

Push-pull outputs offer faster rise time than openrain outputs, and require no pullup resistors.

I/O versions:

8 open-drain I/O ports with latching transition detection interrupt and selectable pullups.

Open-drain outputs can level shift the logic-high state to a higher or lower voltage than V+ using external pullup resistors. Any port can be used as an input by setting the open-drain output to logic-high. Transition flags identify which inputs have changed (even momentarily) since the ports were last read.

4 input-only, 4 output-only versions:

4 input ports with programmable latching transition detection interrupt and selectable pullups;

4 push-pull outputs with selectable power-up default levels.

www.maximintegrated.com

Maxim Integrated │

5

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Table 1. MAX7319MAX7329 Family Comparison (continued)

PART

I

2

C

SLAVE

ADDRESS

INPUTS

INPUT

INTERRUPT

MASK

OPEN-

DRAIN

OUTPUTS

PUSH-

PULL

OUTPUTS

MAX7323 110xxxx Up to 4 — Up to 4 4

APPLICATION

4 I/O, 4 output-only versions:

4 open-drain I/O ports with latching transition detection interrupt and selectable pullups.

4 push-pull outputs with selectable power-up default levels.

8 open-drain I/O ports with nonlatching transition detection interrupt and pullups on all ports.

MAX7328

MAX7329

0100xxx

0111xxx

Up to 8 — Up to 8 — All ports power up as inputs (or logic-high outputs).

Any port can be used as an input by setting the opendrain output to logic-high.

16-PORT EXPANDERS

MAX7324

MAX7325

MAX7326

101xxxx

And

110xxxx

MAX7327

8

Up to 8

4

Up to 4

Yes

Yes

Up to 8

Up to 4

12

12

8

8

Software equivalent to a MAX7320 plus a MAX7319.

Software equivalent to a MAX7320 plus a MAX7321.

Software equivalent to a MAX7320 plus a MAX7322.

Software equivalent to a MAX7320 plus a MAX7323.

case of a bus lockup, terminating any serial transaction to or from the MAX7321.

Any port can be configured as a logic input by setting the port output logic-high (logic-high for an open-drain output is high impedance). When the MAX7321 is read through the serial interface, the actual logic levels at the ports are read back.

The open-drain ports offer latching transition detection when used as inputs. All input ports are continuously monitored for changes. An input change sets 1 of 8 flag bits that identify changed input(s). All flags are cleared upon a subsequent read or write transaction to the

MAX7321.

A latching interrupt output (INT) is programmed to flag logic changes on ports used as inputs. Data changes on any input port forces INT to a logic-low. Changing the I/O port level through the serial interface does not cause an interrupt. The interrupt output INT is deasserted when the MAX7321 is next accessed through the serial interface.

Internal pullup resistors to V+ are selected by the address select inputs (AD0 and AD2). Pullups are enabled on the input ports in groups of four (see Table 3).

Use the slave address selection to ensure that I/O ports used as inputs are logic-high on power-up. I/O ports with internal pullups enabled default to a logic-high output state. Ports with internal pullups disabled default to a logic-low output state. Output port power-up logic states are selected by the address select inputs AD0 and AD2.

Ports default to logic-high or logic-low on power-up in groups of four (see Table 3).

Initial Power-Up

On power-up, the transition detection logic is reset, and

INT is deasserted. The transition flags are cleared to indicate no data changes. The power-up default states of the eight I/O ports are set according to the I

2

C slave address selection inputs, AD0 and AD2 (Table 3).

For

I/O ports used as inputs, ensure that the default states are logic-high so that the I/O ports power up in the high-impedance state. All I/O ports configured with pullups enabled also have a logic-high power-up state.

Power-On Reset

The MAX7321 contains an integral power-on reset

(POR) circuit that ensures all registers are reset to a known state on power-up. When V+ rises above V

POR

(1.6V max), the POR circuit releases the registers and

2-wire interface for normal operation. When V+ drops to less than V

POR

, the MAX7321 resets all register contents to the POR defaults (Table 3).

www.maximintegrated.com

Maxim Integrated │

6

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Table 2. Read and Write Access to Eight-Port Expander Family

PART

I

2

C SLAVE

ADDRESS

INPUTS

INTERRUPT

MASK

OPEN-

DRAIN

OUTPUTS

PUSH-

PULL

OUTPUTS

I

2

C DATA WRITE

MAX7319 110xxxx

MAX7320 101xxxx

MAX7321 110xxxx

8

Up to 8

Yes

Up to 8

8

<I7–I0 interrupt mask>

<O7–O0 port outputs>

<P7–P0 port outputs>

MAX7322 110xxxx 4 Yes — 4

<O7, O6 outputs,

I5–I2 interrupt mask, O1, O0 outputs>

MAX7323 110xxxx

MAX7328 0100xxx

MAX7329 0111xxx

Up to 4

Up to 8

Up to 8

Up to 4

Up to 8

Up to 8

4

<port outputs>

<P7–P0 port outputs>

<P7–P0 port outputs>

I

2

C DATA READ

<I7–I0 port inputs>

<I7–I0 transition flags>

<O7-O0 port inputs>

<P7–P0 port inputs>

<P7–P0 transition flags>

<O7, O6, I5–I2, O1, O0 port inputs>

<0, 0, I5–I2 transition flags,

0, 0>

<O7, O6, P5–P2, O1, O0 port inputs>

<0, 0, P5–P2 transition flags,

0, 0>

<P7–P0 port inputs>

<P7–P0 port inputs>

RST Input

The RST input voids any I

2

C transaction involving the

MAX7321, forcing the MAX7321 into the I

2

C STOP condition. A reset does not affect the INT interrupt output.

Standby Mode

When the serial interface is idle, the MAX7321 automat- ically enters standby mode, drawing minimal supply current.

Slave Address, Power-Up Default Logic

Levels, and Input Pullup Selection

Address inputs AD0 and AD2 determine the MAX7321 slave address, set the power-up I/O state for the ports, and select which inputs have pullup resistors. Internal pullups and power-up default states are set in groups of four (Table 3). The MAX7319, MAX7321, MAX7322, and MAX7323 use a different range of slave addresses

(110xxxx) than the MAX7320 (101xxxx) (Table 2).

The MAX7321 slave address is determined on each I

2

C transmission, regardless of whether the transmission is actually addressing the MAX7321. The MAX7321 distinguishes whether address inputs AD2 and AD0 are connected to SDA or SCL instead of fixed logic levels

V+ or GND during this transmission. This means that the

MAX7321 slave address can be configured dynamically in the application without cycling the device supply.

On initial power-up, the MAX7321 cannot decode address inputs AD0 and AD2 fully until the first I

2

C transmission. AD0 and AD2 initially appear to be connected to V+ or GND. This is important because the address selection is used to determine the power-up logic state and whether pullups are enabled. However, at power-up, the I

2

C SDA and SCL bus interface lines are high impedance at the pins of every device (master or slave) connected to the bus, including the MAX7321.

This is guaranteed as part of the I

2

C specification.

Therefore, address inputs AD2 and AD0 that are connected to SDA or SCL normally appear at power-up to be connected to V+. The power-up logic uses AD0 to select the power-up state and whether pullups are enabled for ports P3–P0, and AD2 for ports P7–P4.

The rule is that a logic-high, SDA, or SCL connection selects the pullups and sets the default logic state to high. A logic-low deselects the pullups and sets the default logic state to low (Table 3). The port configu- ration is correct on power-up for a standard I

2

C configu ration, where SDA or SCL are pulled up to V+ by the external I

2

C pullup resistors.

www.maximintegrated.com

Maxim Integrated │

7

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Table 3. MAX7321 Address Map

SDA

SDA

SDA

SDA

GND

GND

GND

GND

V+

V+

V+

V+

PIN CONNECTION

AD2 AD0

SCL GND

SCL

SCL

SCL

V+

SCL

SDA

GND

V+

SCL

SDA

GND

V+

SCL

SDA

GND

V+

SCL

SDA

1

1

1

1

1

1

A6

1

1

1

1

1

1

1

1

1

1

1

1

1

1

A5

1

1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DEVICE ADDRESS

A4 A3 A2

0 0 0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

0

0

0

0

1

1

0

1

1

0

0

0

1

1

1

1

0

1

0

1

A0

0

1

0

1

1

0

1

0

1

0

1

0

1

1

0

0

A1

0

0

1

1

0

1

1

0

1

0

0

1

Y

Y

Y

Y

Y

Y

I7

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

I6

40k INPUT PULLUP ENABLES

I5 I4 I3 I2 I1

Y Y Y — — —

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

There are circumstances where the assumption that SDA

= SCL = V+ on power-up is not true (e.g., in applications in which there is legitimate bus activity during power-up).

Also, if SDA and SCL are terminated with pullup resistors to a different supply voltage than the MAX7321’s supply voltage, and if that pullup supply rises later than the MAX7321’s supply, then SDA or SCL may appear at power-up to be connected to GND. In such applications, use the four address combinations that are selected by connecting address inputs AD2 and AD0 to V+ or GND

(shown in bold in Table 3). These selections are guaranteed to be correct at power-up, independent of SDA and

SCL behavior. If one of the other 12 address combinations is used, an unexpected combination of pullups might be asserted until the first I

2

C transmission (to any device, not necessarily the MAX7321) is put on the bus, and an unexpected combination of ports may initialize as logic-low outputs instead of inputs or logic-high outputs.

Port Inputs

I/O port inputs switch at the CMOS-logic levels, as determined by the expander’s supply voltage, and are overvoltage tolerant to +6V, independent of the expander’s supply voltage.

I/O Port Input Transition Detection

All I/O ports configured as inputs are monitored for changes since the expander was last accessed through the serial interface. The state of the input ports is stored in an internal

“snapshot” register for transition monitoring. The snapshot is continuously compared with the actual input conditions, and if a change is detected for any port, INT is asserted to signal a state change. An internal transition flag is set for that port. The input is sampled (internally latched into the snapshot register) and the old transition flags cleared during the I

2

C acknowledge of every MAX7321 read and write access. The previous port transition flags are read through the serial interface as the second byte of a

2-byte read sequence.

Y

Y

Y

Y

Y

I0

Y

Y

Y

Y

Y

Y

Y www.maximintegrated.com

Maxim Integrated │

8

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

SDA t

SU,DAT t

SU,STA t

BUF t

LOW t

HD,DAT t

HD,STA t

SU,STO

SCL t

HD,STA t

HIGH t

R t

F

START CONDITION REPEATED START CONDITION

Figure 1. 2-Wire Serial Interface Timing Details

Serial Interface

Serial Addressing

The MAX7321 operates as a slave that sends and receives data through an I

2

C interface. The interface uses a serial-data line (SDA) and a serial-clock line (SCL) to achieve bidirectional communication between master(s) and slave(s). The master initiates all data transfers to and from the MAX7321 and generates the SCL clock that synchronizes the data transfer (Figure 1).

SDA operates as both an input and an open-drain output.

A pullup resistor, typically 4.7kΩ, is required on SDA.

SCL operates only as an input. A pullup resistor, typically

4.7kΩ, is required on SCL if there are multiple masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output.

Each transmission consists of a START condition sent by a master, followed by the MAX7321’s 7-bit slave address plus R/W bit, 1 or more data bytes, and finally a STOP condition (Figure 2).

START and STOP Conditions

Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a START (S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with the slave, the master issues a STOP

(P) condition by transitioning SDA from low to high while

SCL is high. The bus is then free for another transmission

(Figure 2).

Bit Transfer

One data bit is transferred during each clock pulse.

The data on SDA must remain stable while SCL is high

(Figure 3).

STOP

CONDITION

START

CONDITION

SDA

SCL

S

START

CONDITION

P

STOP

CONDITION

Figure 2. START and STOP Conditions

Acknowledge

The acknowledge bit is a clocked 9th bit the recipient uses to acknowledge receipt of each byte of data (Figure 4).

Each byte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA during the acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master is transmitting to the

MAX7321, the MAX7321 generates the acknowledge bit because the device is the recipient. When the MAX7321 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient.

Slave Address

The MAX7321 has a 7-bit-long slave address (Figure 5).

The eighth bit following the 7-bit slave address is the R/W bit. It is low for a write command, and high for a read command.

The first (A6), second (A5), and third (A4) bits of the

MAX7321 slave address are always 1, 1, and 0.

Connect AD2 and AD0 to GND, V+, SDA, or SCL to select slave address bits A3, A2, A1, and A0. The

MAX7321 has 16 possible slave addresses (Table 3), allowing up to 16 MAX7321 devices on an I

2

C bus.

www.maximintegrated.com

Maxim Integrated │

9

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Accessing the MAX7321

The MAX7321 is accessed through an I

2

C interface. The transition flags are cleared, and INT is deasserted each time the device acknowledges the I

2

C slave address.

A single-byte read from the MAX7321 returns the status of the eight I/O ports.

A

2-byte read returns first the status of the eight I/O ports

(as for a single-byte read), followed by the transition flags.

A

multibyte read (more than 2 bytes before the I

2

C

STOP bit) repeatedly returns the port data, alternating with the transition flags. As the port data is resampled for each transmission, and the transition flags are reset each time, a multibyte read continuously returns the current data and identifies any changing ports.

If a port data change occurs during the read sequence,

INT is reasserted after the I

2

C STOP bit. The MAX7321 does not generate another interrupt during a single-byte or multibyte read.

Port data is sampled during the preceding I the case of a single-byte or 2-byte read).

2

C acknowledge bit (the acknowledge bit for the I

2

C slave address in

A single-byte write to the MAX7321 sets the logic state of all eight I/O ports.

A multibyte write to the MAX7321 repeatedly sets the logic state of all eight I/O ports.

Reading from the MAX7321

A read from the MAX7321 starts with the master transmitting the MAX7321’s slave address with the R/W bit set high. The MAX7321 acknowledges the slave address, and samples the ports during the acknowl- edge bit. INT deasserts during the slave address acknowledge.

Typically, the master reads 1 or 2 bytes from the

MAX7321, each byte being acknowledged by the master upon reception with the exception of the last byte.

When the master reads 1 byte from the MAX7321 and subsequently issues a STOP condition (Figure 6), the

MAX7321 transmits the current port data, clears the change flags, and resets the transition detection. INT deasserts during the slave acknowledge. The new snapshot data is the current port data transmitted to the master; therefore, port changes ocurring during the

SDA

SCL

DATA LINE STABLE;

DATA VALID

CHANGE OF DATA

ALLOWED

Figure 3. Bit Transfer

SCL

START

CONDITION

SDA BY

TRANSMITTER

SDA BY

RECEIVER

S

Figure 4. Acknowledge

1 2

CLOCK PULSE

FOR ACKNOWLEDGMENT

8 9 transmission are detected. INT remains high until the

STOP condition.

The master can read 2 bytes from the MAX7321 and then issue a STOP condition (Figure 7). In this case, the MAX7321 transmits the current port data, followed by the change flags. The change flags are then cleared, and transition detection resets. INT goes high (high impedance if an external pullup resistor is not fitted) during the slave acknowledge. The new snapshot data is the current port data transmitted to the master; therefore, port changes occurring during the transmission are detected.

INT remains high until the STOP condition.

www.maximintegrated.com

Maxim Integrated │

10

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

SDA

1

MSB

SCL

Figure 5. Slave Address

1

0

A3 A2 A1 A0

LSB

R/W

ACK

P7 P6 P5

PORT I/O

P4

DATA

P3 P2 P1 P0

S 1 1 0

MAX7321 SLAVE ADDRESS

1

R/W

A D7 D6 D5

PORT SNAPSHOT

D4 D3 D2 D1 D0

PORT SNAPSHOT

N P

SCL t

PH

PORT I/O t

IV

INT OUTPUT

Figure 6. Reading the MAX7321 (1 Data Byte)

t

IR t

PSU

INT REMAINS HIGH UNTIL STOP CONDITION t

IP

I7 I6 I5

PORT I/O

I4 I3 I2 I1 I0 F7 F6

INTERRUPT FLAGS

F5 F4 F3 F2 F1 F0

S 1 1 0

MAX7321 SLAVE ADDRESS

1

R/W

A D7 D6 D5 D4 D3 D2 D1 D0

PORT SNAPSHOT PORT SNAPSHOT

A D7 D6 D5 D4 D3 D2 D1 D0 N

PORT SNAPSHOT

P

SCL t

PH

PORTS t

IV

INT OUTPUT t

IR t

PSU

INT REMAINS HIGH UNTIL STOP CONDITION

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

N = NOT ACKNOWLEDGE t

IP

Figure 7. Reading the MAX7321 (2 Data Bytes)

www.maximintegrated.com

Maxim Integrated │

11

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

INTERNAL WRITE

TO PORT

DATA OUT

FROM PORT

SCL

SDA

S

1 2 3 4 5 6 7 8

SLAVE ADDRESS

0 A

START CONDITION R/W

DATA TO PORT

DATA 1 t

PV

S = START CONDITION SHADED = SLAVE TRANSMISSION

P = STOP CONDITION N = NOT ACKNOWLEDGE t

PV

Figure 8. Writing to the MAX7321

A

Writing to the MAX7321

A write to the MAX7321 starts with the master transmitting the MAX7321’s slave address with the R/W bit set low. The MAX7321 acknowledges the slave address, and samples the ports (takes a snapshot) during acknowledge. INT goes high (high impedance if an external pullup resistor is not fitted) during the slave acknowledge.

Typically, the master proceeds to transmit 1 or more bytes of data. The MAX7321 acknowledges these subsequent bytes of data and updates the I/O ports with each new byte until the master issues a STOP condition (Figure 8).

Applications Information

Port Input and I2C Interface Level

Translation from Higher or Lower

Logic Voltages

The MAX7321’s SDA, SCL, AD0, AD2, RST, INT, and

I/O ports P0–P7 are overvoltage protected to +6V independent of V+. This allows the MAX7321 to operate from a lower supply voltage, such as +3.3V, while the I

2

C interface and/or any of the eight I/O ports are driven as inputs driven from a higher logic level, such as +5V.

The MAX7321 can operate from a higher supply volt- age, such as +3V, while the I

2

C interface and/or some of the I/O ports (P0–P7) are driven from a lower logic level, such as +2.5V. Apply a minimum voltage of

0.7 x V+ to assert a logic-high on any I/O port (e.g., a MAX7321 operating from a +5V supply may not recognize a +3.3V nominal logic-high). One solution for input-level translation is to drive MAX7321 I/Os from open-drain outputs. Use a pullup resistor to V+ or a

DATA TO PORT

DATA 2 t

PV

DATA 1 VALID t

PV

A

DATA 2 VALID higher supply to ensure a high logic voltage greater than 0.7 x V+.

Port-Output Port-Level Translation

The open-drain output architecture allows for level translation to higher or lower voltages than the

MAX7321’s supply. Use an external pullup resistor on any output to convert the high-impedance logic-high condition to a positive voltage level. The resistor can be connected to any voltage up to +6V, and the resistor value chosen to ensure no more than 20mA is sunk in the logic-low condition. For interfacing CMOS inputs, a pullup resistor value of 220kΩ is a good starting point.

Use a lower resistance to improve noise immunity, in applications where power consumption is less critical, or where a faster rise time is needed for a given capac- itive load.

Each of the I/O ports (P0–P7) has a protection diode to

GND (Figure 9). When a port is driven to a voltage lower than GND, the protection diode clamps the voltage to a diode drop below GND.

Each of the P0–P7 I/O ports also has a 40kΩ (typ) pullup resistor that can be enabled or disabled. When a port is driven to a voltage higher than V+, the body diode of the pullup enable switch conducts and the 40kΩ pullup resistor is enabled. When the MAX7321 is powered down (V+ = 0), each I/O port appears as a 40kΩ resistor in series with a diode connected to zero. I/O ports are protected to +6V under any of these circumstances

(Figure 9).

www.maximintegrated.com

Maxim Integrated │

12

MAX7321

Functional Diagram

I

2

C Port Expander with 8 Open-Drain I/Os

AD0

AD2

SCL

SDA

INPUT

FILTER

I

2

C

CONTROL

I/O

PORTS

P7

P6

P5

P4

P3

P2

P1

P0

INT

RST

POWER-

ON RESET

MAX7321

Driving LED Loads

When driving LEDs, a resistor must be fitted in series with the LED to limit the LED current to no more than

20mA. Connect the LED cathode to the MAX7321 port, and the LED anode to V+ through the series current- limiting resistor (R

LED the following formula:

). Set the port output low to illuminate the LED. Choose the resistor value according to

R

LED

= (V

SUPPLY

- V

LED

- V

OL

)/I

LED where:

R

LED

is the resistance of the resistor in series with the

LED (Ω).

V

SUPPLY

is the supply voltage used to drive the LED (V).

V

LED

is the forward voltage of the LED (V).

V

OL

is the output-low voltage of the MAX7321 when sinking I

LED

(V).

I

LED

is the desired operating current of the LED (A).

For example, to operate a 2.2V red LED at 10mA from a

+5V supply:

R

LED

= (5 - 2.2 - 0.07)/0.010 = 270Ω.

PULLUP

ENABLE

INPUT

OUTPUT

V+ V+

40kΩ

Figure 9. MAX7321 I/O Structure

MAX7321

P0–P7 www.maximintegrated.com

Maxim Integrated │

13

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Driving Load Currents Higher than 20mA

The MAX7321 can be used to drive loads, such as relays, that draw more than 20mA by paralleling outputs. Use at least one output per 20mA of load current; for example, a 5V, 330mW relay draws 66mA, and therefore, requires four paralleled outputs. Any combination of outputs can be used as part of a load-sharing design because any combination of ports can be set or cleared at the same time by writing the MAX7321. Do not exceed a total sink current of 100mA for the device.

The MAX7321 must be protected from the negative voltage transient generated when switching off inductive loads (such as relays), by connecting a reverse-biased diode across the inductive load. Choose the peak current for the diode to be greater than the inductive load’s operating current.

Power-Supply Considerations

The MAX7321 operates with a supply voltage of +1.71V to +5.5V over the -40°C to +125°C temperature range.

Bypass the supply to GND with a ceramic capacitor of at least 0.047µF as close as possible to the device. For the TQFN version, additionally connect the exposed pad to GND.

Issue: I

2

C Flag Clearing Deassertion Anomaly

Description of Problem

The MAX7321 clears data stored in the interrupt flag and deasserts the corresponding interrupt when an I ter reads any I

2

C slave on the same bus.

2

C mas-

Workaround

To keep the interrupt flag data valid, the user must read the MAX7321 device BEFORE any other device on the

I

2

C bus, after a pending interrupt. This limits the bus to only one MAX7321 device.

Typical Application Circuit

+3.3V

µ C

SCL

SDA

RST

INT

0.047µF

V+

SCL

SDA

RST

INT

MAX7321

AD0

AD2

GND

P4

P3

P2

P1

P0

P7

P6

P5

Pin Configurations (continued)

TOP VIEW

9 12 11 10

SDA 13

V+ 14

AD0 15

RST 16

MAX7321

+

*EP

1 2 3 4

8

P5

7 P4

6 GND

5 P3

TQFN

*EXPOSED PAD, CONNECTED TO GND

+5V

I/O

I/O

I/O

I/O

Package Information

For the latest package outline information and land patterns

(footprints), go to

www.maximintegrated.com/packages

. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

PACKAGE

TYPE

16 QSOP

PACKAGE

CODE

E16+4

16 TQFN-EP T1633+4

OUTLINE NO.

21-0055

21-0136

LAND

PATTERN NO.

90-0167

90-0031

www.maximintegrated.com

Maxim Integrated │

14

MAX7321 I

2

C Port Expander with 8 Open-Drain I/Os

Revision History

REVISION

NUMBER

0

1

2

3

4

REVISION

DATE

7/05

4/06

7/13

5/14

7/14

DESCRIPTION

Initial release

Updates to data sheet

Added the I

2

C Flag Clearing Deassertion Anomaly section

No /V OPNs; removed automotive reference from Applications section

Revised the Issue: I

2

C Flag Clearing Deassertion Anomaly section

PAGES

CHANGED

1–17

14

1

14

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.

© 2014 Maxim Integrated Products, Inc. │ 15

Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement