MAX7326ATG+T Datasheet MAX7326ATG+T, MAX7326AEG+T, MAX7326ATG+ | P13-P15

MAX7326

C Port Expander with 12 Push-Pull Outputs

and 4 Inputs

______________________________________________________________________________________ 13

The master can read 2 bytes from the group A ports of the

MAX7326 and then issues a STOP condition (Figure 7). In

this case, the MAX7326 transmits the current port data,

followed by the transition flags. The transition flags are

then cleared, and transition detection restarts. 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, and

therefore, port transitions occuring during the transmission

are detected. INT remains high until the STOP condition.

A read from the group B ports of the MAX7326 starts

with the master transmitting the group’s slave address

with the R/W bit set high. The MAX7326 acknowledges

the slave address and samples the logic state of the

output ports during the acknowledge bit. The master

can read one or more bytes from the output ports of the

MAX7326, and then issues a STOP condition (Figure 8).

The MAX7326 transmits the current port data, read

back from the actual port outputs (not the port output

latches) during the acknowledge bit. If a port is forced

to a logic state other than its programmed state, the

readback reflects this. If driving a capacitive load, the

readback port level verification algorithms may need to

take the RC rise/fall time into account.

Typically, the master reads one byte from the group B

ports of the MAX7326, then issues a STOP condition

(Figure 8). However, the master can read two or more

bytes from the output ports of the MAX7326, and then

issues a STOP condition. In this case, the MAX7326

resamples the port outputs during each acknowledge

and transmits the new data each time.

SCL

MAX7326 SLAVE ADDRESSSA P1

PORTS

INT OUTPUT

R/W

ACKNOWLEDGE

FROM MAX7326

ACKNOWLEDGE

FROM MASTER

PORT SNAPSHOT

I2I3I4I5

D0D1D2D3D4D5D6D7

PORT SNAPSHOT

F2F3F4F5

D7 D6 D5 D4 D3 D2 D1 D0 A

PORT SNAPSHOT

FLAG

INT REMAINS HIGH UNTIL STOP CONDITION

S = START CONDITION

P = STOP CONDITION

A = ACKNOWLEDGE

Figure 7. Reading Group A Ports of the MAX7326 (2 Data Bytes)

SCL

MAX7326 SLAVE ADDRESS

ACKNOWLEDGE FROM MAX7326

PORT SNAPSHOT DATA

PORT SNAPSHOT TAKEN

P0P1P2P3

DATA 1

P4P5P6P7

D0D1D2D3D4D5D6D7

PORT SNAPSHOT TAKEN

ACKNOWLEDGE

FROM MASTER

R/W

S = START CONDITION

P = STOP CONDITION

A = ACKNOWLEDGE

Figure 8. Reading Group B Ports of the MAX7326

MAX7326

C Port Expander with 12 Push-Pull Outputs

and 4 Inputs

14 ______________________________________________________________________________________

SCL

SDA

START CONDITION ACKNOWLEDGE

FROM SLAVE

SLAVE ADDRESS

12345678

AAA

DATA 1 DATA 2

DATA 2 VALIDDATA 1 VALID

WRITE

TO PORT

DATA OUT

FROM PORT

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

DATA TO PORT DATA TO PORT

R/W

Figure 10. Writing to the Group B Ports of the MAX7326

Writing to the MAX7326

A write to the group A ports of the MAX7326 starts with

the master transmitting the group’s slave address with

the R/W bit set low. The MAX7326 acknowledges the

slave address and samples the ports during the

acknowledge. INT goes high (high impedance if an

external pullup resistor is not fitted) during the slave

address acknowledge. The master can then issue a

STOP condition after the acknowledge (Figure 6), but

typically the master proceeds to transmit one or more

bytes of data. The MAX7326 acknowledges these sub-

sequent bytes of data and updates the four output

ports and the 4-bit interrupt mask register with each

new byte until the master issues a STOP condition

(Figure 9).

A write to the group B ports of the MAX7326 starts with

the master transmitting the group’s slave address with

the R/W bit set low. The MAX7326 acknowledges the

slave address and samples the ports during the

acknowledge bit. The master can now transmit one or

more bytes of data. The MAX7326 acknowledges these

subsequent bytes of data and updates the correspond-

ing group’s ports with each new byte until the master

issues a STOP condition (Figure 10).

SCL

SDA

START CONDITION R/W

SLAVE ADDRESS

12345678

AAA

DATA 1 DATA 2

DATA TO INTERRUPT MASK DATA TO INTERRUPT MASK

Figure 9. Writing to the Group A Ports of the MAX7326

MAX7326

C Port Expander with 12 Push-Pull Outputs

and 4 Inputs

______________________________________________________________________________________ 15

Applications Information

Port Input and I

C Interface Level

Translation from Higher or Lower

Logic Voltages

The MAX7326’s SDA, SCL, AD0, AD2, RST, INT, and

I2–I5 are overvoltage protected to +6V independent of

V+. This allows the MAX7326 to operate from a lower

supply voltage, such as +3.3V, while the I

C interface

and/or any of the four input ports are driven from a

higher logic level, such as +5V.

The MAX7326 can operate from a higher supply volt-

age, such as +3V, while the I

C interface and/or some

of the four input ports I2–I5 are driven from a lower

logic level, such as +2.5V. For V+ < 1.8V, apply a mini-

mum voltage of 0.8 x V+ to assert a logic-high on any

input. For V+ ≥ 1.8V, apply a voltage of 0.7 x V+ to

assert a logic-high. For example, a MAX7326 operating

from a +5V supply may not recognize a +3.3V nominal

logic-high. One solution for input level translation is to

drive the MAX7326 inputs from open-drain outputs. Use

a pullup resistor to V+ or a higher supply to ensure a

high logic voltage of greater than 0.7 x V+.

Port Output Signal Level Translation

Each of the push-pull output ports (O0, O1, and

O6–O15) has protection diodes to V+ and GND (Figure

11). When a port output is driven to a voltage higher

than V+ or below GND, the appropriate protection

diode clamps the output to a diode drop above V+ or

below GND. Do not overvolt output ports O0, O1, and

O6–O15. When the MAX7326 is powered down (V+ =

0), each output port appears as a diode clamp to GND

(Figure 11).

Each of the four input ports I2–I5 has a protection diode

to GND (Figure 12). When a port input is driven to a

voltage lower than GND, the protection diode clamps

the output to a diode drop below GND.

Each of the four input ports (I2–I5) also has a 40kΩ

(typ) pullup resistor that can be enabled or disabled.

When a port input 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

MAX7326 is powered down (V+ = 0), each input port

appears as a 40kΩ resistor in series with a diode con-

nected to zero. Input ports are protected to +6V under

any of these circumstances (Figure 12).

Driving LED Loads

When driving LEDs from one of the 12 output ports (O0,

O1, or O6–O15), 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 MAX7326 port, and

the LED anode to V+ through the series current-limiting

resistor, R

LED

. Set the port output low to light the LED.

I2–I5

PULLUP

ENABLE

INPUT

40kΩ

V+

MAX7326

Figure 12. MAX7326 Input Port StructureFigure 11. MAX7326 Push-Pull Output Port Structure

OUTPUT

V+V+

O0, O1,

O6–O15

MAX7326

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P20

MAX7326ATG+T

Mfr. #:

Buy MAX7326ATG+T

Manufacturer:

Maxim Integrated

Description:

Interface - I/O Expanders I2C Port Expander w/12 P-P Out & 4 In

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MAX7326ATG+T

MAX7326ATG+T

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