The "BQ27421YZFR-G1A" is a fuel gauge IC manufactured by Texas Instruments. It is designed to provide accurate state-of-charge (SOC) measurement for lithium-ion and lithium-polymer batteries.
Here is a detailed explanation of the pin function specifications and circuit principle instructions for this device, focusing on the package and the pinout details.
1. Package and Pinout Overview
The BQ27421YZFR-G1A comes in a QFN-20 (Quad Flat No-leads) package, which has 20 pins in total. This package is typically used for small-sized ICs and is designed for surface-mount applications. Below is the complete pinout description and functionality for each of the 20 pins.
2. Pinout and Function Table
Pin Number Pin Name Pin Type Pin Description 1 VSTOR Power Battery voltage input. Connect to the battery positive terminal. 2 GND Power Ground pin. Connect to the system ground. 3 SDA I2C Serial data input/output. Used for I2C communication. 4 SCL I2C Serial clock input. Used for I2C communication. 5 ALERT Output Active low signal that indicates an alert condition (such as low battery). 6 TS Analog Thermistor input for battery temperature sensing. 7 BAT Analog Battery voltage sense input. Connect to the battery positive terminal. 8 CHG Output Charging status output. Indicates the charging state of the battery. 9 C/10 Output Indicates when the battery current drops below 1/10th of the full-scale current. 10 SLEEP Input Sleep mode control. Low signal puts the IC into low power sleep mode. 11 OCV Output Open-circuit voltage. Outputs the battery's open-circuit voltage. 12 PGOOD Output Power good signal. Indicates that the system is powered up and operating correctly. 13 STAT Output Status indicator. Reflects various states such as charge, discharge, etc. 14 DNP Reserved Do not connect. Should be left floating or unconnected. 15 DNP Reserved Do not connect. Should be left floating or unconnected. 16 DNP Reserved Do not connect. Should be left floating or unconnected. 17 DNP Reserved Do not connect. Should be left floating or unconnected. 18 DNP Reserved Do not connect. Should be left floating or unconnected. 19 VSS Ground Ground pin. Connect to the system ground. 20 VDD Power Supply voltage input. Typically connected to 3.3V to 5V depending on the system.3. Circuit Principle
The BQ27421YZFR-G1A is a fuel gauge that uses impedance tracking technology to estimate the state of charge (SOC) and remaining capacity of the battery. The fuel gauge communicates with the host processor using the I2C interface (pins SDA and SCL), allowing the host to read battery parameters such as voltage, temperature, current, and remaining capacity.
The battery voltage is supplied through the VSTOR pin, while the BAT pin senses the battery voltage to measure the SOC. The thermistor is connected to the TS pin to monitor the temperature of the battery, ensuring that it operates within safe limits. The CHG, PGOOD, ALERT, and STAT pins provide status feedback to the system, indicating the charging status, power conditions, and error states.
4. FAQ: 20 Common Questions
Q: What is the function of the VSTOR pin on the BQ27421YZFR-G1A? A: The VSTOR pin is used to connect to the positive terminal of the battery, providing the input voltage for the fuel gauge.
Q: Can I connect the SDA and SCL pins of the BQ27421YZFR-G1A to a non-I2C bus? A: No, the SDA and SCL pins are specifically for I2C communication. You must connect them to an I2C bus.
Q: What happens if I leave the ALERT pin floating? A: The ALERT pin should not be left floating. It is an active low signal that indicates alert conditions. If unused, it can be pulled high.
Q: Can I use the BQ27421YZFR-G1A without connecting the thermistor to the TS pin? A: The thermistor connected to the TS pin is important for temperature monitoring of the battery. If it's not connected, the fuel gauge may not provide accurate temperature readings.
Q: What is the significance of the STAT pin on the BQ27421YZFR-G1A? A: The STAT pin provides status information such as charge or discharge state. It helps in monitoring the battery’s operation.
Q: How do I put the BQ27421YZFR-G1A into sleep mode? A: To enter sleep mode, pull the SLEEP pin low. This reduces power consumption.
Q: What voltage should I apply to the VDD pin of the BQ27421YZFR-G1A? A: The VDD pin should be connected to a supply voltage of 3.3V to 5V, depending on the system requirements.
Q: How can I check the battery’s open-circuit voltage using the BQ27421YZFR-G1A? A: The OCV pin outputs the open-circuit voltage of the battery. You can measure this using a voltmeter.
Q: Is it necessary to connect the VSS pin to ground? A: Yes, the VSS pin must be connected to the ground of the system to complete the circuit.
Q: What is the function of the C/10 pin on the BQ27421YZFR-G1A? A: The C/10 pin is used to indicate when the battery current drops below 1/10th of the full-scale current.
Q: Can I use the BQ27421YZFR-G1A with any type of battery? A: The BQ27421YZFR-G1A is designed for use with lithium-ion and lithium-polymer batteries.
Q: What is the purpose of the PGOOD pin? A: The PGOOD pin indicates whether the system is powered correctly. It signals power-up status.
Q: Is it possible to interface the BQ27421YZFR-G1A with a microcontroller? A: Yes, you can interface it with a microcontroller using the I2C communication (SDA and SCL pins).
Q: How do I interpret the charging status from the BQ27421YZFR-G1A? A: The CHG pin provides the charging status. When the battery is charging, this pin is active.
Q: What should I do if the BQ27421YZFR-G1A is not responding? A: Ensure that the VDD and VSTOR pins are properly connected and that the I2C lines are functioning. Check for any hardware faults.
Q: Can I use the BQ27421YZFR-G1A in a non-portable system? A: Yes, it can be used in both portable and non-portable applications, as long as a lithium-ion or lithium-polymer battery is used.
Q: What are the temperature monitoring capabilities of the BQ27421YZFR-G1A? A: The IC uses the thermistor connected to the TS pin to monitor the battery's temperature.
Q: How does the BQ27421YZFR-G1A measure state of charge (SOC)? A: The fuel gauge uses impedance tracking to estimate the battery’s state of charge by monitoring voltage, current, and temperature.
Q: What is the role of the DNP pins on the BQ27421YZFR-G1A? A: The DNP pins are "Do Not Connect" and should be left unconnected. They are not used in the operation of the device.
Q: Is there a way to customize the battery parameters on the BQ27421YZFR-G1A? A: Yes, the BQ27421YZFR-G1A can be configured using its I2C interface to customize parameters such as charging thresholds, current calibration, and other settings.
This explanation provides the detailed functionality for each pin of the BQ27421YZFR-G1A, as well as answers to common questions about its operation.