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MAX7325 Datasheet(PDF) 7 Page - Maxim Integrated Products |
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MAX7325 Datasheet(HTML) 7 Page - Maxim Integrated Products |
7 / 17 page MAX7325 I2C Port Expander with 8 Push-Pull and 8 Open-Drain I/Os 7 Maxim Integrated The open-drain ports offer latching transition detection when used as inputs. All input ports are continuously monitored for changes. An input change sets one of 8 flag bits that identify changed input(s). All flags are cleared upon a subsequent read or write transaction to the MAX7325. 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 deassert- ed when the MAX7325 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 2). 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 out- put state. I/O ports with internal pullups disabled default to a logic-low output state. Output port power-up logic levels 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 Tables 2 and 3). Initial Power-Up On power-up, the transition detection logic is reset, and INT is deasserted. The transition flags are cleared to indi- cate no data changes. The power-up default states of the 16 I/O ports are set according to the I2C slave address selection inputs, AD0 and AD2 (Tables 2 and 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 MAX7325 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 VPOR (1.6V max), the POR circuit releases the registers and 2-wire interface for normal operation. When V+ drops to less than VPOR, the MAX7325 resets all register con- tents to the POR defaults (Tables 2 and 3). RST Input The active-low RST input voids any I2C transaction involving the MAX7325, forcing the MAX7325 into the I2C STOP condition. A reset does not affect the inter- rupt output (INT). Standby Mode When the serial interface is idle, the MAX7325 automatical- ly 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 MAX7325 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 (see Table 2). The MAX7325 slave address is determined on each I2C transmission, regardless of whether the transmission is actually addressing the MAX7325. The MAX7325 distin- guishes whether address inputs AD0 and AD2 are con- nected to SDA or SCL instead of fixed logic levels V+ or GND during this transmission. The MAX7325 slave address can be configured dynamically in the applica- tion without cycling the device supply. On initial power-up, the MAX7325 cannot decode the address inputs AD0 and AD2 fully until the first I2C transmission. AD0 and AD2 initially appear to be PART I2C SLAVE ADDRESS INPUTS INPUT INTERRUPT MASK OPEN- DRAIN OUTPUTS PUSH- PULL OUTPUTS CONFIGURATION MAX7323 110xxxx Up to 4 — Up to 4 4 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. MAX7328 MAX7329 0100xxx 0111xxx Up to 8 — Up to 8 — 8 open-drain I/O ports with nonlatching transition detection interrupt and pullups on all ports. Table 1. MAX7319–MAX7329 Family Comparison (continued) |
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