ZHCSHN9B February 2018 – February 2025 LMK05028
PRODUCTION DATA
The HW_SW_CTRL input pin selects the device start-up mode that determines the memory page used to initialize the registers, serial interface, and logic pin functions at power-on reset. The initial register settings determine the device's frequency configuration stored in the internal EEPROM (NVM) or ROM. After start-up, the device registers can be accessed through the selected serial interface for device status monitoring or programming, and the logic pins will function as defined by the mode configuration.
| 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:
After POR, GPIO[6:3] can function the same as for HW_SW_CTRL = 0 if enabled by registers. |
To provide 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 host device (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.