SI4320-J1-FT

April 17, 2012 Si4x3x Errata (rev. B) Errata Status Summary Errata # Title Impact Status 1 Register modification required for frequency operation from 240–320 MHz and 480–640 MHz. Minor Work around is available. 2 Incorrect nIRQ signal operation after shutdown (SDN) or initial power up. Minor Work around is available 3 Current draw may be higher than expected when in SLEEP mode when the Low Battery Detection (LBD) function is ENABLED. Major Multiple software workarounds are available. Impact Definition: Each erratum is marked with an impact, as defined below:  Minor: Workaround exists.  Major: Errata that do not conform to the data sheet or standard.  Information: The device behavior is acceptable the data sheet will be changed to match the device behavior. 400 West Cesar Chavez, Austin, TX 78701 (512) 416-8500 FAX (512) 416-9669 www.silabs.com S4x3xB0ER041712 Errata Details 1. Description: Register modifications are required for operation in the frequency bands between 240–320 MHz and 480–640 MHz with a temperature above 60 °C. Impact: In extremely rare cases, the synthesizer will not lock in these bands when the device is operated at a temperature above 60 °C. The software workaround is only required for these frequency and temperature ranges. Workaround: Write 03h to register 59h and 02h to register 5Ah. Resolution: Software workaround with register modification. 2. Description: Incorrect nIRQ signal operation after shutdown (SDN) or initial power up. Impacts: In a small percentage of cases after Shutdown (SDN) or initial power up the nIRQ signal can be low during the Power-on-Reset (POR) period. Typically the nIRQ signal will be high during this period and will exhibit a high to low transition at the expiration of the POR period. The interrupt status registers in 03h and 04h will report the correct status of the POR and the nIRQ function is normal after the initial POR period. Workaround: The nIRQ line should not be monitored for POR after SDN or initial power up. The POR signal is available by default on GPIO0 and GPIO1 and should be monitored as an alternative to nIRQ for POR. A second potential workaround is also available by running a timer on the microcontroller after SDN for 26 ms and then reading the interrupt status registers in 03h and 04h to check for POR and chip ready (XTAL start-up/ready). After the initial interrupt is cleared the operation of the nIRQ pin will be normal. Resolution: Will be fixed in the next revision. 3. Description: This issue ONLY affects SLEEP mode when the low battery detection (LBD) function is ENABLED (enlbd = 1 in Register 07h). Note that the LBD function is DISABLED by default. If LBD is ENABLED, approximately 5% of devices will enter into a state that draws more current than expected in SLEEP mode. Such devices will draw an average current of approximately 350 µA in SLEEP mode versus the expected 1 µA. These devices will also report an inaccurate battery voltage level in SLEEP mode. The cause of the issue has been verified to be the improper reset of the LBD circuitry when in SLEEP mode. We strongly recommend all customers affected by this issue to implement one of the software workarounds described below. Impact: Affected devices will draw more current than expected in SLEEP mode which will reduce the battery life of battery-backed products. Workaround: If the low battery detection (LBD) function is not required during SLEEP mode, this issue can be resolved by ensuring that LBD is DISABLED (enlbd = 0 in Register 07h). 400 West Cesar Chavez, Austin, TX 78701 (512) 416-8500 FAX (512) 416-9669 www.silabs.com Alternatively, we have verified two software workarounds that allow the battery level to be checked during SLEEP mode with low current consumption. Complete details and reference code are provided in the attached Appendix. A summary of each workaround is included below. Workaround A: This workaround utilizes the Low Duty Cycle Mode function of the device to periodically check the battery level. The wake-up timer (WUT) period must be set in conjunction with the LDC mode on time to 0.5 s for this workaround to function properly. It does not require any intervention by an external MCU. The average current when using this workaround is 2.5 µA. Workaround B: This workaround requires an external MCU to wake up the device and check battery levels periodically. The average current when using this workaround is dependent on the duty cycle of the wake up interval. If the interval is set to 500 s, the average current in this mode will be 1 µA. Resolution: Implementation of the workarounds described in this document will enable the battery level to be checked with low current consumption. The low battery detection (LBD) function is no longer recommended for use in SLEEP mode and will be removed from the next revision of the Si4x3x data sheet. 400 West Cesar Chavez, Austin, TX 78701 (512) 416-8500 FAX (512) 416-9669 www.silabs.com Appendix Workaround A: This Low Battery Detection using Low Duty Cycle Mode (automatic LBD workaround). Initialize Chip, Clear Interrupts Setup wake-up timer, low duty cycle mode to 0.5 sec Enable Low Battery Detect interrupt Enable Low Duty Cycle Mode Low Battery Detect Interrupt? N Y Indicate Low Battery Clear Interrupts 400 West Cesar Chavez, Austin, TX 78701 (512) 416-8500 FAX (512) 416-9669 www.silabs.com Workaround B: Low Battery Detection Using Wake-Up Timer. Initialize Chip Clear Interrupts Setup wake-up timer to 1 sec. (or desired time) Enable wake-up timer interrupts Go to Sleep Mode Wake Up Timer Interrupt ? N Y Wait for some time Read Battery Voltage Battery Voltage < Low Battery Detect Threshold? Y Indicate Low Battery N Clear Interrupts 400 West Cesar Chavez, Austin, TX 78701 (512) 416-8500 FAX (512) 416-9669 www.silabs.com Sample Code Workaround A: Low Battery Detection using Low Duty Cycle Mode //Function PROTOTYPES //MCU initialization void MCU_Init(void); //SPI functions void SpiWriteRegister (U8, U8); U8 SpiReadRegister (U8); // GLOBAL VARIABLE xdata U16 wWaitCnt; void main(void) { U8 ItStatus1,ItStatus2,Battery_Voltage_Level,LBDT; U16 delay; U8 temp8; //Initialize the MCU: // - set IO ports for the Software Development board // - set MCU clock source // - initialize the SPI port // - turn off LEDs MCU_Init(); //Initialize the Si4x3x ISM chip //read interrupt status registers to clear the interrupt flags and release NIRQ pin ItStatus1 = SpiReadRegister(0x03); //read the Interrupt Status1 register ItStatus2 = SpiReadRegister(0x04); //read the Interrupt Status2 register for (temp8=0;temp8