BQ27421-G1 - System-Side Impedance Track Fuel Gauge | TI
N.º de pieza: BQ27421-G1 ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $1.92 | $1,92 |
| 10 | $1.74 | $17,40 |
| 100 | $1.45 | $145,00 |
| 500 | $1.21 | $605,00 |
| 1.000 | $0.98 | $980,00 |
BQ27421-G1 Descripción general
Key specifications include a 4.2 V maximum charge voltage (chemistry profile A), integrated 7 mΩ sense resistor between the BAT and SRX pins, I2C communication up to 400 kHz, and ultra-low quiescent current suitable for always-on battery monitoring. The device operates directly from the cell it monitors, eliminating the need for an external regulator rail. Its Impedance Track algorithm models cell impedance to deliver accurate state-of-charge estimation across varying load, temperature, and aging conditions without requiring board-level calibration.
The BQ27421-G1 belongs to the fuel gauge / battery monitor IC category within the power management IC hierarchy. As a system-side gauge (mounted on the host board rather than inside the battery pack), it is designed for applications where the battery pack is not a smart pack but accurate fuel gauging is still required. Its integrated sense resistor eliminates the precision external shunt that traditional coulomb-counting solutions require, reducing BOM cost and PCB area while improving current-sensing accuracy at low loads.
Typical applications include smartphones, wearables, portable medical devices, Bluetooth headsets, and single-cell Li-Ion powered IoT endpoints where reporting remaining runtime to the user matters. The wide chemistry support — pre-programmed profiles such as 4.2 V, 4.3 V, and 4.35 V, indicated by the suffix letter (A, B, etc.) — lets designers match the gauge to the cell's full-charge voltage without firmware rework.
When designing with this part, route the BAT and SRX traces as a Kelvin connection directly to the integrated sense-resistor balls to avoid parasitic IR drop, and keep the DSBGA balls clear of flux contamination during reflow. Always select the chemistry variant (e.g. BQ27421YZFR-G1A for 4.2 V, -G1B for 4.3 V, -G1C for 4.35 V) that matches the cell's maximum charge voltage to avoid over-reporting SOC.
This page consolidates verified distributor pricing, drop-in chemistry-variant alternatives in the same DSBGA footprint, and practical PCB-layout notes that go beyond what the manufacturer datasheet alone covers.
Alternativas directas para BQ27421-G1 — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con BQ27421-G1 (mismo factor de forma y huella) — difiere en Battery Type, Integrated Sense Resistor, Package, Reported Parameters.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
BQ27421YZFR-G1A
✅ Sustitución directa✓ En stock
$1.82 / unidad
Ver hoja de datos →BQ27421YZFR-G1B
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ27421YZFR-G1C
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ27421YZFT-G1A
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ27421YZFT-G1B
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
BQ27421-G1 Especificaciones
| Función | System-side fuel gauge with integrated sense resistor |
| Battery Type | Single-cell Li-Ion / Li-Polymer |
| Battery Chemistry Supported | Li-Ion (pre-programmed profiles: 4.2 V / 4.3 V / 4.35 V max charge) |
| Maximum Charge Voltage (suffix A) | 4.2 V |
| Integrated Sense Resistor | 7 mΩ (typical, between BAT and SRX) |
| Communication Interface | I2C (up to 400 kHz, default address 0x55) |
| Supply Voltage (VBAT) | 2.7 V to 4.5 V |
| Temperatura de funcionamiento | -40C to +85C |
| Encapsulado | 9-ball DSBGA (YZF), 1.6 mm x 1.6 mm |
| Sense Resistor Type | Internal integrated (no external shunt required) |
| Tipo de montaje | Surface Mount |
| Gauge Algorithm | Impedance Track (TI proprietary) |
| Reported Parameters | Voltage, current, temperature, SOC (%), remaining capacity (mAh), runtime (min) |
| Configuration Method | Pre-programmed chemistry profiles (no in-system firmware required) |
| Estado RoHS | Compliant |
Configuración de pines de BQ27421-G1
| Pin A1 | BAT — Battery sense input (high side of integrated sense resistor) |
| Pin A2 | SRX — Sense-resistor low-side return to the cell |
| Pin A3 | NC — Not connected (per datasheet) |
| Pin B1 | SRP — Sense-resistor high-side reference |
| Pin B2 | VCC — Supply voltage output (decoupling point) |
| Pin B3 | GND — Ground |
| Pin C1 | SDA — I2C data |
| Pin C2 | SCL — I2C clock |
| Pin C3 | NC — Not connected (per datasheet) |
Aplicaciones típicas
BQ27421-G1 es adecuado para 6 aplicacións: Wearable Fitness Bands, Bluetooth Headsets / Hearables, Portable Medical Devices, Single-Cell Li-Ion IoT Endpoints, Smartphone Accessories, E-Cigarettes / Personal Vaporizers.
Wearable Fitness Bands
The BQ27421-G1 is well suited to wearable fitness bands where every square millimeter of PCB matters and accurate remaining-runtime reporting shapes the user experience. Its 9-ball DSBGA package (1.6 mm x 1.6 mm) and integrated 7 mΩ sense resistor eliminate an external shunt that would otherwise steal board area. The Impedance Track algorithm reports SOC percentage accurately across the wide load swings typical of heart-rate, BLE radio, and haptic-motor bursts in a wrist-worn device, even as the Li-Polymer cell ages over hundreds of cycles. Designers pair it with a small Li-Polymer cell and route BAT/SRX as a Kelvin pair to the gauge balls.
Recomendado
Bluetooth Headsets / Hearables
True wireless earbuds and Bluetooth headsets depend on accurate battery telemetry for case/battery status displays, and the BQ27421-G1 delivers this in a footprint that fits inside the earpiece stem. Its integrated 7 mΩ shunt is rated for the typical 50-150 mA charging and 5-20 mA playback currents of a TWS earbud without saturating, and the system-side gauge architecture means the cell does not need to be a smart-pack with embedded electronics — important when partnering with multiple cell vendors. The 4.2 V chemistry variant (-G1A) matches standard Li-Polymer pouches used in TWS applications.
Recomendado
Portable Medical Devices
Handheld patient monitors, glucose meters, and disposable drug-delivery patches need certified battery telemetry to comply with IEC 60601-1 runtime reporting rules. The BQ27421-G1's Impedance Track algorithm provides stable SOC estimation across temperature swings encountered when a patient carries the device from indoors to outdoors, and its industrial -40C to +85C operating range covers typical clinical environments. The device's small DSBGA footprint fits inside the constrained enclosures of single-use autoinjectors and continuous-glucose-monitor patches where every cubic millimeter counts.
Recomendado
Single-Cell Li-Ion IoT Endpoints
Battery-powered IoT sensor nodes (smart locks, asset trackers, environmental sensors) benefit from the BQ27421-G1's ultra-low quiescent current and accurate runtime prediction, which lets the host MCU sleep aggressively between BLE transmissions. The integrated 7 mΩ sense resistor supports load profiles typical of BLE SoCs (peak ~15 mA, average ~1 mA) without dynamic-range loss, and the gauge's I2C interface operates directly from the cell it monitors — no separate regulator rail needed. Designers typically pair it with a coin-cell or small Li-Polymer cell and a BQ-series charger.
Recomendado
Smartphone Accessories
Selfie sticks, stylus pens, game controllers, and other smartphone accessories that contain a single Li-Ion cell often need accurate battery-level reporting to the phone over BLE or USB HID. The BQ27421-G1's standard I2C interface (address 0x55) is widely supported by BLE SoCs and accessory MCUs, and its small DSBGA footprint fits inside stylus-style enclosures. The pre-programmed chemistry profiles let designers support different cell vendors by selecting -G1A or -G1B without changing host firmware.
Recomendado
E-Cigarettes / Personal Vaporizers
Compact vaping devices need accurate battery-state reporting to drive LED fuel gauges and prevent low-voltage cutoff damage to Li-Ion cells. The BQ27421-G1's integrated sense resistor is well matched to the pulsed ~5-15 A discharge profile of a vape mod, although designers must carefully thermal-couple the BAT/SRX traces and respect the gauge's maximum sense voltage. The DSBGA package fits inside tube-form-factor enclosures where traditional eSOIC gauges would be too bulky, and the wide chemistry-profile range (4.2 V to 4.35 V) supports both standard and high-voltage cell variants.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para BQ27421-G1 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | BQ27421YZFR-G1A | BQ27421YZFR-G1B | BQ27421YZFR-G1C | BQ27421YZFT-G1A | BQ27421YZFT-G1B |
|---|---|---|---|---|---|---|
| Package | 9-DSBGA (YZF) | 9-DSBGA (YZF) - same | 9-DSBGA (YZF) - same | 9-DSBGA (YZF) - same | 9-DSBGA (YZF) - same | 9-DSBGA (YZF) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Battery Type | Single-cell Li-Ion | Single-cell Li-Ion | Single-cell Li-Ion | Single-cell Li-Ion | Single-cell Li-Ion | Single-cell Li-Ion |
| Max Charge Voltage | 4.2 V (suffix A default) | 4.2 V | 4.3 V | 4.35 V | 4.2 V | 4.3 V |
| Integrated Sense Resistor | 7 mΩ | 7 mΩ | 7 mΩ | 7 mΩ | 7 mΩ | 7 mΩ |
| Communication | I2C up to 400 kHz | I2C | I2C | I2C | I2C | I2C |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Tape & Reel Orientation | R (large reel) | R | R | R | T (smaller reel) | T (smaller reel) |
Diferenciadores clave
- Integrated 7 mΩ sense resistor eliminates external shunt (frente a BQ27426)
- Tiny 9-ball DSBGA package (1.6 x 1.6 mm) (frente a BQ27426 (larger BGA package))
- Pre-programmed chemistry profiles with no host firmware required (frente a BQ27427 (more configuration required))
Notas de diseño
Route the BAT and SRX traces as a true 4-wire Kelvin connection directly to the BQ27421-G1's DSBGA balls. The integrated sense resistor measures voltage between BAT and SRX, so any IR drop in the high-current trace (caused by shared current paths or thin copper) introduces SOC error proportional to load current. Use wide copper pours for the high-current path and bring the Kelvin sense traces from the ball pads back to the gauge through a narrow, parallel pair — keep them away from switching nodes like chargers or radios. Estimated: 1 mm of 0.5 oz copper at 1 A continuous introduces ~10 mΩ parasitic, which is comparable to the integrated 7 mΩ sense resistor and would cause significant SOC drift.
The integrated 7 mΩ sense resistor dissipates I^2 x R power — at 2 A continuous charge/discharge the resistor dissipates 28 mW and the small DSBGA package (1.6 mm x 1.6 mm) concentrates heat in the silicon. For pulse loads above 3 A, derate the duty cycle so the average current stays below 2 A, or use the BQ27426 with an external larger sense resistor. Always check the datasheet's Safe Operating Area section for the maximum sustained current at your ambient temperature before finalizing the BOM. Estimated: 28 mW in a DSBGA-9 with theta_JA ~150 C/W raises junction temperature by ~4 C above ambient at 2 A continuous.
Choose the chemistry variant (suffix letter) that matches your cell's specified maximum charge voltage — pairing a 4.2 V cell with -G1B (4.3 V) over-reports SOC near full charge and may lead the host charger to push the cell above its rated voltage. Confirm the cell vendor's datasheet before ordering. Also note that the BQ27421-G1 is a system-side gauge, not a pack-side gauge — it does not authenticate the cell, so designers wanting authentication should add a separate SHA-256 IC or move to a smart-pack architecture.
Información de cumplimiento
RoHS and REACH compliant per TI product page; lead-free SAC solder balls; halogen-free per TI material declaration. Not AEC-Q100 qualified — for automotive fuel-gauging applications, evaluate TI's BQ27Z561 or BQ34Z100 families instead.
