MAX7324ATG+ Datasheet MAX7324AEG+, MAX7324AEG+T, MAX7324ATG+ | P13-P15

MAX7324

C Port Expander with Eight Push-Pull Outputs

and Eight Inputs

______________________________________________________________________________________ 13

When the master reads 2 bytes from the output ports of

the MAX7324 and subsequently issues a STOP condi-

tion (Figure 7), the MAX7324 transmits the current port

data, followed by the transition flags. The transition

flags are then cleared, and transition detection is reset.

INT deasserts 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. When the master reads more than

2 data bytes, the input port data alternates with the

transition flag.

A read from the output ports of the MAX7324 starts with

the master transmitting the ports’ slave address with

the R/W bit set high. The MAX7324 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

MAX7324, and then issues a STOP condition (Figure 8).

The MAX7324 transmits the current port data, read

back from the actual port outputs (not the port output

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

logic state other than its programmed state, the read-

back reflects this. If driving a capacitive load, the read-

back port level verification algorithms may need to take

the RC rise/fall time into account.

Typically, the master reads one byte from the ouput

ports of the MAX7324, then issues a STOP condition

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

bytes from the output ports of the MAX7324, and then

issues a STOP condition. In this case, the MAX7324

resamples the port outputs during each acknowledge

and transmits the new data each time.

SCL

MAX7324 SLAVE ADDRESSSA P1

PORTS

ACKNOWLEDGE

FROM MAX7324

ACKNOWLEDGE

FROM MASTER

PORT SNAPSHOT

I2I3I4I5

D0D1D2D3D4D5D6D7

PORT SNAPSHOT

F2F3F4F5

D7 D6 D5 D4 D3 D2 D1 D0 A

PORT SNAPSHOT

FLAG

INT OUTPUT

R/W

S = START CONDITION A = ACKNOWLEDGE

P = STOP CONDITION

INT REMAINS HIGH UNTIL STOP CONDITION

Figure 7. Reading Input Ports of the MAX7324 (2 Data Bytes)

SCL

MAX7324 SLAVE ADDRESS

ACKNOWLEDGE FROM MAX7324

PORT SNAPSHOT DATA

PORT SNAPSHOT TAKEN

P0P1P2P3

DATA 1

P4P5P6P7

D0D1D2D3D4D5D6D7

PORT SNAPSHOT TAKEN

ACKNOWLEDGE

FROM MASTER

R/W

Figure 8. Reading Output Ports of the MAX7324

MAX7324

C Port Expander with Eight Push-Pull Outputs

and Eight Inputs

14 ______________________________________________________________________________________

Writing to the MAX7324

A write to the input ports of the MAX7324 starts with the

master transmitting the group’s slave address with the

R/W bit set low. The MAX7324 acknowledges the slave

address and samples the ports during the acknowl-

edge bit. INT deasserts during the slave acknowledge.

The master can now transmit one or more bytes of

data. The MAX7324 acknowledges these subsequent

bytes of data and updates the interrupt mask register

with each new byte until the master issues a STOP con-

dition (Figure 9).

A write to the output ports of the MAX7324 starts with

the master transmitting the group’s slave address with

the R/W bit set low. The MAX7324 acknowledges the

slave address and samples the ports during the

acknowledge bit. The master can now transmit one or

more bytes of data. The MAX7324 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 Input Ports of the MAX7324

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 Output Ports of the MAX7324

MAX7324

C Port Expander with Eight Push-Pull Outputs

and Eight Inputs

______________________________________________________________________________________ 15

Applications Information

Port Input and I

C Interface Level

Translation from Higher or Lower

Logic Voltages

SDA, SCL, AD0, AD2, RST, INT, and I0–I7 are overvolt-

age protected to +6V. This allows the MAX7324 to

operate from a lower supply voltage, such as +3.3V,

while the I

C interface and/or any of the eight input

ports are driven from a higher logic level, such as +5V.

The MAX7324 can operate from a higher supply volt-

age, such as +3V, while the I

C interface and/or some

of the input ports I0–I7 are driven from a lower logic

level, such as +2.5V. For V+ < 1.8V, apply a minimum

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 MAX7324 operating from a

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

high. One solution for input level translation is to drive

the MAX7324 inputs from open-drain outputs. Use a

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

logic voltage greater than 0.7 x V+.

Port Output Signal Level Translation

RST, SCL, SDA, AD0, and AD2 remain high impedance

with up to +6V asserted on them when the MAX7324 is

powered down (V+ = 0). The MAX7324 can therefore

be used in hot-swap applications.

Each of the eight output ports has protection diodes to

V+ and GND. When a port output is driven to a voltage

higher than V+ or lower than GND, the appropriate pro-

tection diode clamps the output to a diode drop above

V+ or below GND. When the MAX7324 is powered

down (V+ = 0), every output port's protection diodes to

V+ and GND continue to appear as a diode clamp from

each output to GND (Figure 11).

Each of the input ports I0–I7 has a protection diode to

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

age lower than GND, the protection diode clamps the

voltage to a diode drop below GND.

Each of the eight input ports I0–I7 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

MAX7324 is powered down (V+ = 0), every input port

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

nected to ground. Input ports are protected to +6V

under any of these circumstances.

Driving LED Loads

When driving LEDs from one of the eight output ports,

O8–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 MAX7324 port, and the LED anode

to V+ through the series current-limiting resistor, R

LED

I0–I7

PULLUP

ENABLE

INPUT

40kΩ

V+

MAX7324

Figure 12. MAX7324 Input Port Structure

OUTPUT

V+

GNDGND

V+

O8–O15

MAX7324

Figure 11. MAX7324 Output Port Structure

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

MAX7324ATG+

Mfr. #:

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Manufacturer:

Maxim Integrated

Description:

Interface - I/O Expanders I2C Port Expander w/8 P-P Out & 8 In

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MAX7324ATG+

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