STC3117IJT

STC3117 Gas gauge IC with battery charger control for handheld applications Datasheet - production data Description The STC3117 includes the STMicroelectronics OptimGauge™ algorithm. It provides accurate battery state-of-charge (SOC) monitoring, tracks battery parameter changes with operation conditions, temperature, and aging, and allows the application to get a battery state-of-health (SOH) indication. An alarm output signals low SOC or low voltage conditions and also indicates fault conditions like a missing or swapped battery. CSP (1.49 x 1.594 mm) Features  Patented OptimGauge™ algorithm for accurate  battery capacity calculation  Robust initial open-circuit-voltage (OCV) measurement at power up  Programmable low battery alarm  Missing/swapped battery detection  Average current internal calculation  End-of-charge detection  Internal temperature sensor  Battery swap detection with protection against false battery insertion  Low power: 40 µA in voltage-only mode, 2 µA max in standby mode  1.49 x 1.594 mm 9-bump CSP package Applications  Mobile phones, multimedia players, digital cameras  Portable medical equipment November 2017 This is information on a product in full production. DocID025792 Rev 3 1/35 www.st.com Contents STC3117 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 6 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1 6.2 7 8 2/35 Battery monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 6.1.1 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1.2 Battery voltage monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1.3 Internal temperature monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1.4 Current sensing in mixed mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1.5 SOC change rate in voltage mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 STC3117 gas gauge architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2.1 Coulomb counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2.2 Voltage gas gauge algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.2.3 Mixed mode gas gauge system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.3 Alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.4 Current monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.5 Power-up and battery swap detection . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 I2C interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.1 Read and write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.2 Register map and description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.2.1 Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.2.2 Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.2.3 REG_MODE and REG_CTRL register description . . . . . . . . . . . . . . . . 25 7.2.4 OCV table register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 DocID025792 Rev 3 STC3117 Contents 8.1 Flip Chip CSP 1.49 x 1.594 x 0.4 mm (N5) with coating ball  printing package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 DocID025792 Rev 3 3/35 35 Block diagram 1 STC3117 Block diagram Figure 1. STC3117 internal block diagram VCC BATD CD Battery detection and charge control 1.2 V reference 32768 Hz time base Temperature sensor control logic & ALM state machine Oscillator AD converter VIN MUX CS+ control registers CS- SCL SDA I2C interface RAM and ID registers GND 4/35 DocID025792 Rev 3 CS STC3117 2 Pin assignment Pin assignment Table 1. STC3117 pin description CSP bump pin no. Pin name Type(1) C3 ALM O/OD Alarm signal output, open drain,  external pull-up with resistor A2 SDA I/OD I2C serial data B2 SCL I_D I2C serial clock A3 GND Ground B3 CS I_A Current sensing input B1 BATD I/OA Battery detection input A1 CD O/OD Battery charge inhibit (active high output) C2 VCC Supply Power supply C1 VIN I_A Function Analog and digital ground Battery voltage sensing input 1. I = input, 0 = output, OD = open drain, A = analog, D = digital, NC = not connected Figure 2. STC3117 pin connections (top view) CD SDA GND BATD SCL CS VIN VCC ALM CSP (1.49 x 1.594 mm) Top view (balls are underneath) DocID025792 Rev 3 5/35 35 Absolute maximum ratings and operating conditions 3 STC3117 Absolute maximum ratings and operating conditions Table 2. Absolute maximum ratings Symbol VCCMAX VIO TSTG TJ Parameter Value Maximum voltage on VCC pin Unit 6 V Voltage on I/O pins -0.3 to 6 Storage temperature -55 to 150 Maximum junction temperature Electrostatic discharge (HBM: human body model)(1) ESD Electrostatic discharge (MM: machine C 150 model)(2) 2 kV 150 V 1. Tested in compliance with MIL-883-H, AEC-Q100-002D and JEDEC JESD22-A114F 2. Tested in compliance with MIL-883-H, AEC-Q100-003E and JEDEC JESD22-A115A Table 3. Operating conditions Symbol Parameter VCC Operating supply voltage on VCC VMIN Minimum voltage on VCC for RAM content retention TOPER V 2.0 -40 to 85 -20 to 70 DocID025792 Rev 3 Unit 2.7 to 4.5 Operating free air temperature range TPERF 6/35 Value C STC3117 4 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20C to 70C) Symbol Parameter Conditions Min Typ Max Units Supply ICC Average value over 4 s in voltage mode 40 Average value over 4 s in mixed mode 80 Operating current consumption ISTBY Current consumption in standby Standby mode,  inputs = 0 V BATD_PU bit = 0 IPDN Current consumption in power-down VCC < UVLOTH,  inputs = 0 V UVLOTH Undervoltage threshold (VCC decreasing) UVLOHYST Undervoltage threshold hysteresis POR Power-on reset threshold µA 2.5 (VCC decreasing) 2.6 2 1 2.7 V 100 mV 2.0 V Current sensing Vin_gg Input voltage range IIN Input current ADC_res AD converter granularity ADC_offset AD converter offset ADC_time AD conversion time ADC_acc AD converter gain accuracy at full scale (using external sense resistor) FOSC Internal time base frequency Osc_acc Internal time base accuracy -40 mV 500 nA 5.88 CS = 0 V -3 µV 3 500 25 C LSB ms 0.5 % Over temperature range 1 32768 25 C, VCC = 3.6 V Cur_res +40 Hz 2 % Over temperature and voltage ranges 2.5 Current register LSB value 5.88 µV Battery voltage and temperature measurement Vin_adc Input voltage range LSB LSB value VCC = 4.5 V 0 Voltage measurement Temperature measurement ADC_time AD conversion time Volt_acc 2.7 V < Vin < 4.5 V,  Battery voltage measurement accuracy VCC = Vin, 25 C Over temperature range Temp_acc Internal temperature sensor accuracy DocID025792 Rev 3 4.5 V 2.20 mV 1 °C 250 ms -0.25 +0.25 -0.5 +0.5 -3 3 % °C 7/35 35 Electrical characteristics STC3117 Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20C to 70C) (continued) Symbol Parameter Conditions Min Typ Max Units 0.35 V Digital I/O pins (SCL, SDA, ALM) Vih Input logic high Vil Input logic low Vol Output logic low (SDA, ALM) 1.2 Iol = 4 mA 0.4 Analog I/O pins (BATD, CD) Vith BATD input threshold voltage 1.46 1.61 Vihyst BATD input voltage hysteresis 0.1 Ru BATD internal pull-up resistor 1 Vcdoh CD output logic high Ioh = 3 mA Vinmin_cd Minimum Vin voltage for CD operation 0°C to 50°C 1.76 V 8/35 DocID025792 Rev 3 M VCC - 0.4 3.6 3.75 3.9 V STC3117 Electrical characteristics Table 5. I2C timing - VIO = 2.8 V, Tamb = -20 °C to 70 C (unless otherwise specified) Symbol Parameter Min Fscl SCL clock frequency thd,sta Hold time (repeated) START condition 0.6 tlow LOW period of the SCL clock 1.3 thigh HIGH period of the SCL clock 0.6 tsu,sta Setup time for repeated START condition 0.6 thd,dat Data hold time 0 tsu,dat Data setup time 100 Typ 0 Max Unit 400 kHz µs 0.9 tr Rise time of both SDA and SCL signals 20+ 0.1Cb tf Fall time of both SDA and SCL signals 20+ 0.1Cb tsu,sto Setup time for STOP condition 0.6 tbuf Bus free time between a STOP and START condition 1.3 Cb Capacitive load for each bus line — 300 300 ns µs 400 pF Figure 3. I2C timing diagram 9LK 6'$ WI 9LO WKGVWD WU WVXGDW WKLJK 6&/ WORZ WKGGDW WVXVWD *$3060' DocID025792 Rev 3 9/35 35 Application information 5 STC3117 Application information Figure 4. Example of an application schematic Optional filter IO voltage VCC SCL SDA STC3117 C1 R1 VIN C2 Other detection circuit Battery pack BATD ALM R2 Rid CS CD GND Rs Table 6. External component list Name Value Rs 5 to 50 m C1 1 µF C2 220 nF Tolerance Comments 1 % to 5 % Current sense resistor (2% or better recommended) Supply decoupling capacitor Battery voltage input filter (optional) R1 1 k R2 10/35 Battery detection function DocID025792 Rev 3 STC3117 Functional description 6 Functional description 6.1 Battery monitoring functions 6.1.1 Operating modes The monitoring functions include the measurement of battery voltage, current, and temperature. A Coulomb counter is available to track the SOC when the battery is charging or discharging at a high rate. A sigma-delta A/D converter is used to measure the voltage, current, and temperature. The STC3117 can operate in two different modes with different power consumption (see Table 7. Mode selection is made by the VMODE bit in register 0 (refer to Table 12 for register 0 definition). Table 7. STC3117 operating modes VMODE Description 0 Mixed mode, Coulomb counter is active, voltage gas gauge runs in parallel 1 Voltage gas gauge with power saving Coulomb counter is not used. No current sensing. In mixed mode, current is measured continuously (except for a conversion cycle every 4 s and every 16 s for measuring voltage and temperature respectively). This provides the highest accuracy from the gas gauge. In voltage mode with no current sensing, a voltage conversion is made every 4 s and a temperature conversion every 16 s. This mode provides the lowest power consumption. It is possible to switch between the two operating modes to get the best accuracy during active periods, and to save power during standby periods while still keeping track of the SOC information. 6.1.2 Battery voltage monitoring Battery voltage is measured by using one conversion cycle of the A/D converter every 4 s. The conversion cycle takes 213 = 8192 clock cycles. Using the 32768 Hz internal clock, the conversion cycle time is 250 ms. The voltage range is 0 to 4.5 V and resolution is 2.20 mV. Accuracy of the voltage measurement is ±0.5 % over the temperature range. This allows accurate SOC information from the battery open-circuit voltage. The result is stored in the REG_VOLTAGE register (see Table 11). DocID025792 Rev 3 11/35 35 Functional description 6.1.3 STC3117 Internal temperature monitoring The chip temperature (close to the battery temperature) is measured using one conversion cycle of the A/D converter every 16 s. The conversion cycle takes 213 = 8192 clock cycles. Using the 32768 Hz internal clock, the conversion cycle time is 250 ms. Resolution is 1° C and range is -40 to +125 °C. The result is stored in the REG_TEMPERATURE register (see Table 11). 6.1.4 Current sensing in mixed mode Current sensing is available only in mixed mode (VMODE=0). The voltage drop across the sense resistor is integrated during a conversion period and is input to the 14-bit sigma-delta A/D converter. Using the 32768 Hz internal clock, the conversion cycle time is 500 ms for a 14-bit resolution. The LSB value is 5.88 µV. The A/D converter output is in two’s complement format. When a conversion cycle is completed, the result is added to the Coulomb counter accumulator and the number of conversions is incremented in a 16-bit counter. The current register is updated after each conversion (that is: once per 500-ms measurement cycle). The result is stored in the REG_CURRENT register (see Table 11). Average current register In mixed mode, an average value of the current measurement is calculated after each current measurement with a time constant of 2 s. The register REG_AVG_CURRENT (2 bytes) holds the average current when VMODE=0. The LSB of REG_AVG_CURRENT is 1/4 the LSB of REG_CURRENT, that is 1.47 µV. 6.1.5 SOC change rate in voltage mode Current sensing is not available in voltage mode (VMODE=1). Instead, an estimation of the SOC change rate is provided in the REG_AVG_CURRENT register. The SOC change rate is updated after each SOC calculation (that is: once per 4-s measurement cycle) and is averaged with a time constant of 64 seconds. It is possible to write an initial estimation into the REG_AVG_CURRENT register to speed-up the SOC change rate settling time. The REG_AVG_CURRENT register (2 bytes) holds the SOC change rate when VMODE=1. The LSB of REG_AVG_CURRENT is 0.008789 C (by definition, 1 C means 100% SOC change in 1 h). 12/35 DocID025792 Rev 3 STC3117 Functional description 6.2 STC3117 gas gauge architecture 6.2.1 Coulomb counter The Coulomb counter is used to track the SOC of the battery when the battery is charging or discharging at a high rate. Each current conversion result is accumulated (Coulomb counting) for the calculation of the relative SOC value based on the configuration register. The system controller can control the Coulomb counter and set and read the SOC register through the I2C control registers. Figure 5. Coulomb counter block diagram 16-bit counter REG_COUNTER register REG_CURRENT register current filter REG_AVG_CURRENT register EOC Coulomb counter calculator CS GND AD converter To SOC management REG_CC_CNF register The REG_CC_CNF value depends on battery capacity and the current sense resistor. It scales the charge integrated by the sigma delta converter into a percentage value of the battery capacity. The default value is 395 (corresponding to a 10-m sense resistor and 1957-mAh battery capacity). The Coulomb counter is inactive if the VMODE bit is set, this is the default state at poweron-reset (POR) or reset (VMODE bit = 1). Writing a value to the register REG_SOC (mixed mode SOC) forces the Coulomb counter gas gauge algorithm to restart from this new SOC value. REG_CC_CNF register is a 16-bit integer value CC_CNF that is calculated as shown in Equation 1: Equation 1 CC_CNF = Rsense  Cnom  49.556 Rsense is in mand Cnom is in mAh. Example: Rsense =10 m, Cnom = 1500 mAh, CC_CNF = 303 DocID025792 Rev 3 13/35 35 Functional description 6.2.2 STC3117 Voltage gas gauge algorithm No current sensing is needed for the voltage gas gauge. An internal algorithm precisely simulates the dynamic behavior of the battery and provides an estimation of the OCV. The battery SOC is related to the OCV by means of a high-precision reference OCV curve built into the STC3117. Any change in battery voltage causes the algorithm to track both the OCV and SOC values, taking into account the non-linear characteristics and time constants related to the chemical nature of the Li-Ion and Li-Po batteries. A single parameter fits the algorithm to a specific battery. The default value provides good results for most battery chemistries used in hand-held applications. Figure 6. Voltage gas gauge block diagram REG_VOLTAGE register REG_VM_CNF register REG_OCV VIN register AD converter Voltage mode (VM) algorithm To SOC management REG_OCVTAB Reference OCV curve register REG_SOCTAB register Voltage gas gauge algorithm registers The REG_VM_CNF configuration register is used to configure the parameter used by the algorithm based on battery characteristic. The default value is 321 (corresponding to  160 m internal battery impedance and 1957 mAh Cnom battery capacity). The REG_OCV register holds the estimated OCV value corresponding to the present battery state. The REG_OCVTAB and REG_SOCTAB registers define the OCV curve for a given battery type; the default power-up values can be updated at software initialization. The REG_VM_CNF register is a 12-bit integer value and is calculated from the averaged internal resistance and nominal capacity of the battery as shown in Equation 2: Equation 2 VM_CNF = Ri  Cnom  977.78 Ri is in mand Cnom is in mAh. Example: Ri = 250 m, Cnom =1500 mAh, VM_CNF= 384 14/35 DocID025792 Rev 3 STC3117 6.2.3 Functional description Mixed mode gas gauge system The STC3117 implements a mixed mode gas gauge (OptimGaugeTM 1) that uses both the Coulomb counter (CC) and the voltage mode (VM) algorithm to track the battery SOC in all application conditions and automatically provide the optimum SOC information. The VM algorithm cancels any long-term errors and prevents the SOC drift problem that is commonly found in CC-only solutions. The STC3117 automatically selects the best method based on the relaxation timer (see Section 6.4: Current monitoring) as follows: when a low-power application state is detected by the relaxation timer, the SOC reported by the STC3117 is the VM SOC, otherwise the CC SOC is reported. The STC3117 manages the transitions between the VM and CC modes without discontinuity by adjusting the VM and the CC SOC to ensure smooth SOC variations without jumps in any application conditions. The current mixed mode state is indicated by the GG_VM bit in the REG_CTRL register: GG_VM=1 means the reported SOC is the VM SOC, otherwise the SOC is the CC SOC. Note: When the application enters standby mode, the STC3117 can be put into power-saving mode by setting the VMODE bit to 1 in the REG_MODE register. Only the VM gas gauge stays active, the CC is stopped, and the power consumption is reduced. Figure 7. Mixed mode gas gauge block diagram Voltage mode (VM) gas gauge SOC management Coulomb counter (CC) REG_SOC register Alarm management REG_VM_ADJ register Parameter tracking REG_CC_ADJ register Adjustment registers The registers REG_CC_ADJ and REG_VM_ADJ are signed 16-bit registers. They accumulate the adjustment quantities made to the SOC values by the embedded mixed mode algorithm:  REG_CC_ADJ = REG_SOC – (unadjusted CC SOC)  REG_VM_ADJ = REG_SOC – (unadjusted VM SOC) These registers can be used by the system application to implement more sophisticated algorithms for improved performance and accuracy. Writing to the REG_SOC or REG_OCV initializes the two VM and CC algorithms to the corresponding SOC value and clears REG_VM_ADJ and REG_CC_ADJ. It is possible to write to the REG_SOC, REG_OCV, REG_VM_CNF and REG_CC_CNF registers when the STC3117 is running without disturbing SOC management. Note: When writing to the REG_SOC or REG_OCV registers, the resulting SOC value is rounded to the nearest 1/64 % value (the least three bits of REG_SOC are zero). DocID025792 Rev 3 15/35 35 Functional description 6.3 STC3117 Alarm output The ALM pin provides an alarm signal in case of low battery or fault condition. The output is an open drain, and an external pull-up resistor is needed in the application. Writing the IO0DATA bit to 0 forces the ALM output low; writing the IO0DATA bit to 1 lets the ALM output reflect the battery condition. Reading the IO0DATA bit gives the state of the ALM pin. When the IO0DATA bit is 1, the ALM pin is driven low if any of the following conditions are met:  the battery SOC estimation from the mixed algorithm is less than the programmed threshold (if the alarm function is enabled by the ALM_ENA bit)  the battery voltage is less than the programmed low voltage level (if the ALM_ENA bit is set)  the BATFAIL bit is set (if the ALM_ENA bit is set) Low-voltage or low-SOC alarms When a low-voltage or low-SOC condition is triggered, the STC3117 drives the ALM pin low and sets the ALM_VOLT or ALM_SOC bit in REG_CTRL. The ALM pin remains low (even if the conditions disappear) until the software writes the ALM_VOLT and ALM_SOC bits to 0 to clear the interrupt. Clearing the ALM_VOLT or ALM_SOC while the corresponding low-voltage or low-SOC condition is still true does not generate another interrupt; this condition must disappear first and must be detected again before another interrupt (ALM pin driven low) is generated for this alarm. The other alarm condition, if not yet triggered, can still generate an interrupt. Usually, the low-SOC alarm occurs first to warn the application of a low battery condition, then if no action is taken and the battery discharges further, the low-voltage alarm signals a nearly-empty battery condition. At power-up, or when the STC3117 is reset, the SOC and voltage alarms are enabled (ALM_ENA bit = 1). The ALM pin is in high-impedance directly after a POR and is driven low if the SOC and/or the voltage is below the default thresholds (1% SOC, 3.00 V), after the first OCV measurement and SOC estimation. The REG_SOC_ALM register holds the relative SOC alarm level in 0.5 % units (0 to 100 %). Default value is 2 (i.e. 1 % SOC). The REG_ALARM_VOLTAGE holds the low voltage threshold and can be programmed over the full scale voltage range with 17.60 (2.20*8) mV steps. Default value is 170 (i.e. 3.00 V). BATFAIL alarm The BATFAIL bit in REG_CTRL reflects the battery swap event: BATFAIL bit is set when the BATD signal rises above the BATD threshold (1.61 V typ) for more than 0.5 s. and is reset by writing 0 to the BATFAIL bit if the BATD signal is below the BATD threshold (if BATD is still above 1.61 V, then BATFAIL bit can not be cleared). The STC3117 drives the ALM pin low when the BATFAIL bit is set and releases the ALM pin when the BATFAIL bit is cleared. 16/35 DocID025792 Rev 3 STC3117 6.4 Functional description Current monitoring The battery average current is monitored and is used in conjunction with a timer to implement a battery relaxation timer. Battery relaxation timer The battery relaxation timer is used to detect a light-load, low-power condition. The REG_CMONIT_COUNT register is an 8-bit, read-only counter that is incremented every 4 s when the average current is inside a window defined by positive and negative thresholds set by the REG_CURRENT_THRES register, and decremented every 500 ms when the current is outside the thresholds. When the counter reaches its maximum value set by the REG_CMONIT_MAX register, a low-power condition is reported to the mixed mode algorithm causing VM mode to be used. When the counter reaches its minimum value (0), a high-power condition is reported and CC mode is used. The REG_CMONIT_MAX register sets the maximum value of the counter. With the default value (120 dec), the counter provides an 8-minute delay when switching from CC to VM mode and a 1-minute delay when switching from VM to CC mode. The REG_CURRENT_THRES register is an 8-bit R/W register set by the gas gauge firmware from the I2C. It holds the threshold amplitude in bits 0 to 6 (unsigned value applicable for both positive and negative thresholds). Bit 7 of REG_CURRENT_THRES is reserved and must be set to zero for operation of the current monitoring counter as a relaxation timer. The LSB value of the REG_CURRENT_THRES is 47.04 µV and provides a range of 0 to 6 mV. It is possible to set the counter to zero or the maximum value using the FORCE_CC and FORCE_VM bits in the REG_MODE register. These bits are self-clearing. DocID025792 Rev 3 17/35 35 Functional description 6.5 STC3117 Power-up and battery swap detection When the STC3117 is powered up at first battery insertion (power-on reset) or after a soft reset condition (PORDET bit set by host), an automatic battery voltage, current and temperature measurement cycle is made immediately after startup and debounce delay. This feature enables the system controller to get the SOC of a newly inserted battery based on the OCV. The CD pin controls the battery charger to inhibit the charge during the initial OCV measurement. The CD output is validated during the power-up/restart sequence but is actually driven high only if the battery is present (BATD < 1.61V) and the battery voltage is higher than a threshold (Vin > Vinmin_cd) at the beginning of the restart sequence. The CD pin can be driven high under software control by using the bit FORCE_CD in the REG_MODE register. The BATD pin senses the presence of the battery independently of the battery voltage. Figure 8. BATD and CD internal architecture overview VCC CD_drive & CD BATD 1.61 V + - Vin Vinmin_cd level + - The BATD pin is an analog I/O. The input detection threshold is typically 1.61 V. The CD pin is an output connected to the VCC level when active. Otherwise, it is high impedance. The BATD pin can be connected to the NTC sensor or to the identification resistor of the battery pack. By default, the STC3117 provides an internal pull-up resistor for the detection of battery removal. The internal resistor can be disabled by clearing the bit BATD_PU in the REG_MODE register. When disabled, an external pull-up resistor or another device has to pull the BATD pin high. 18/35 DocID025792 Rev 3 STC3117 Functional description Figure 9. Timing diagram details of the power-up and restart sequence OCV meas. Ibat meas. delay VCC Application can start, charge is enabled “Good” battery Vinmin_cd UVLO (arbitrary Vcc waveforms only to illustrate the function) “Dead” battery Internal 1mA sink current “Good” battery “Dead” battery CD pin (low means HiZ) 375 ms Voltage measurement Current measurement Temperature measurement Conversion counter X 100 ms 0 125 ms 125 ms 1 2 125 ms 250 ms 3 GAMS1601141520CB Battery swap detection A battery swap can be detected in two ways:  the battery voltage drops below the undervoltage lockout (UVLO) for more than tdel  the BATD signal rises above the BATD threshold (1.61 V typ) for more than tdel The tdel delay is 0.5 s. Using the 0.5 s filter provides robust battery swap detection and prevents false battery swap detection if short contact bouncing occurs at the battery terminals due to mechanical vibrations or shocks. This also prevents false detections in case of short battery voltage drops and protects the application against high surge currents at low temperatures. Following a battery swap detection and after the battery voltage goes back above UVLO and the BATD level returns to low level, the STC3117 is on hold with new voltage and current measurements in the corresponding registers. The system has to restart the STC3117 by doing a device soft reset i.e. by setting the PORDET bit to 1 in the REG_CTRL register and restoring the parameters (if needed). To recover the event, either use the measured voltage and current to define a new OCV voltage, or restore a previous SOC state. The occurrence of the battery swap event is indicated by the BATFAIL and UVLOD bits in the REG_CTRL register. DocID025792 Rev 3 19/35 35 Functional description STC3117 Figure 10. Restart in case of battery swap