SNAS801B June 2020 – June 2021 LMK05318B
PRODUCTION DATA
The HW_SW_CTRL input pin selects the device start-up mode that determines the memory page (EEPROM or ROM) used to initialize the registers, the serial interface, and the logic pin functions at power-on reset. The initial register settings determine the frequency configuration of the device on start-up. After start-up, the device registers can be accessed through the serial interface for device monitoring and programming, and the logic pins will function as defined by the selected mode.
HW_SW_CTRL INPUT LEVEL(1) | START-UP MODE | MODE DESCRIPTION |
---|---|---|
0 | EEPROM + I2C (Soft pin mode) | Registers are initialized from EEPROM, and I2C interface is enabled. Logic pins:
|
Float (VIM) | EEPROM + SPI (Soft pin mode) | Registers are initialized from EEPROM, and SPI interface is enabled. Logic pins:
|
1 | ROM + I2C (Hard pin mode) | Registers are initialized from the ROM page selected by GPIO pins, and I2C interface is enabled. Logic pins:
|
To ensure proper start-up into EEPROM + SPI Mode, the HW_SW_CTRL, STATUS0, and STATUS1 pins must all be floating or biased to VIM (0.8-V typical) before the PDN pin is pulled high. These three pins momentarily operate as 3-level inputs and get sampled at the low-to-high transition of PDN to determine the device start-up mode during POR. If any of these pins are connected to a system host (MCU or FPGA), TI recommends using external biasing resistors on each pin (10-kΩ pullup to 3.3 V with 3.3-kΩ pulldown to GND) to set the inputs to VIM during POR. After power up, the STATUS pins can operate as LVCMOS outputs to overdrive the external resistor bias for normal status operation.