BQ79881-Q1 - Automotive UIR Sensor with Pack-Level EIS | TI
MPN: BQ79881-Q1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $12.5 | $12.50 |
| 10 | $11.2 | $112.00 |
| 100 | $9.85 | $985.00 |
| 500 | $8.6 | $4,300.00 |
| 1,000 | $7.45 | $7,450.00 |
BQ79881-Q1 Overview
Background: A UIR Sensor is a specialized battery management IC that combines cell voltage monitoring, current sensing, pack-level EIS, and insulation resistance (also called isolation or hipot) monitoring in a single device. In modern EV/HEV high-voltage battery packs, the BMS must measure cell voltages, sense pack current via a shunt, perform AC impedance spectroscopy to assess state-of-health, and continuously verify the high-voltage isolation between the pack and the chassis (a safety-critical function to detect creepage or breakdown). The BQ79881-Q1 integrates all of these functions into one ASIL-D-capable IC, reducing PCB area and BOM cost versus discrete implementations. It sits in the broader taxonomy: battery monitor IC -> battery management -> power management -> semiconductor.
Key features include AEC-Q100 qualification for automotive applications, integrated EIS engine for state-of-health diagnostics, dedicated single-ended measurement paths, and 5us typical VI synchronization. The device supports ISO 26262 functional safety at ASIL-D for HV measurement accuracy (<0.4%). The LQFP-48 package with exposed thermal pad provides robust thermal performance for underbody automotive environments.
Typical applications include EV/HEV battery management systems, high-voltage battery junction boxes, stationary energy storage systems, and industrial battery backup systems requiring ASIL-D functional safety. The pack-level EIS function enables in-situ battery health monitoring without disconnecting the battery pack.
When designing with this device, pay attention to the high-voltage isolation layout, the shunt resistor placement for current sensing, and the host MCU communication interface timing. The BQ79881-Q1 is typically paired with a BQ79718-Q1 cell monitor and a host MCU running TI's BMS firmware stack.
Drop-in alternatives for BQ79881-Q1 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with BQ79881-Q1 (same form factor and footprint) — differing in Functional Safety, Package, Automotive Qualification, Function, Mounting Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
BQ79826Z-Q1
✅ Drop-In✓ In Stock
$12.4 / Unit
View Datasheet →BQ79616-Q1
✅ Drop-In✓ In Stock
$10.4 / Unit
View Datasheet →BQ79631-Q1
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
BQ79600-Q1
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$1.65 / Unit
View Datasheet →BQ79617-Q1
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
BQ79881-Q1 Maximum Ratings & Electrical Characteristics
| Product Type | UIR Sensor with Pack-Level EIS |
| Function | Battery monitor with EIS, voltage, current, insulation resistance monitoring |
| HV Measurement Accuracy | <0.4% (ASIL-D) |
| Single-Ended Measurement Range | 0.3 V to 5 V |
| Pack Voltage Measurements | 2 (fast) |
| VI Sync within BQ79881 | 0 us |
| VI Sync with Cell Monitor | 5 us typical |
| Functional Safety | ASIL-D capable (ISO 26262) |
| Automotive Qualification | AEC-Q100 |
| Package | LQFP-48 (7x7 mm) with EP |
| Mounting Type | Surface Mount |
| EIS Engine | Integrated (pack-level) |
| Insulation Resistance Monitoring | Yes (UIR function) |
| Target Application | EV/BMS HV Automotive |
| RoHS Status | Compliant |
BQ79881-Q1 Pin Configuration
| Pin 1 | VIO — Digital I/O supply |
| Pin 2 | GPIO1 — General-purpose I/O |
| Pin 3 | GPIO2 — General-purpose I/O |
| Pin 4 | CSN — SPI chip select (active low) |
| Pin 5 | SCLK — SPI clock |
| Pin 6 | MOSI — SPI master-out slave-in |
| Pin 7 | MISO — SPI master-in slave-out |
| Pin 8 | nRESET — Hardware reset (active low) |
| Pin 9 | INT — Interrupt output |
| Pin 10 | TX — UART transmit |
| Pin 11 | RX — UART receive |
| Pin 12 | DGND — Digital ground |
| Pin 13 | AVDD — Analog supply |
| Pin 14 | AGND — Analog ground |
| Pin 15 | REF — Internal reference bypass |
| Pin 16 | VC0 — Cell voltage input 0 |
| Pin 17 | VC1 — Cell voltage input 1 |
| Pin 18 | VC2 — Cell voltage input 2 |
| Pin 19 | VC3 — Cell voltage input 3 |
| Pin 20 | VC4 — Cell voltage input 4 |
| Pin 21 | VC5 — Cell voltage input 5 |
| Pin 22 | VC6 — Cell voltage input 6 |
| Pin 23 | VC7 — Cell voltage input 7 |
| Pin 24 | VC8 — Cell voltage input 8 |
| Pin 25 | VC9 — Cell voltage input 9 |
| Pin 26 | VC10 — Cell voltage input 10 |
| Pin 27 | VC11 — Cell voltage input 11 |
| Pin 28 | VC12 — Cell voltage input 12 |
| Pin 29 | VC13 — Cell voltage input 13 |
| Pin 30 | VC14 — Cell voltage input 14 |
| Pin 31 | VC15 — Cell voltage input 15 |
| Pin 32 | SRP — Shunt resistor positive input |
| Pin 33 | SRN — Shunt resistor negative input |
| Pin 34 | PACKP — Pack voltage positive input |
| Pin 35 | PACKN — Pack voltage negative input |
| Pin 36 | UIRP — Insulation monitor positive |
| Pin 37 | UIRN — Insulation monitor negative |
| Pin 38 | TSENSE1 — Temperature sensor input 1 |
| Pin 39 | TSENSE2 — Temperature sensor input 2 |
| Pin 40 | TSENSE3 — Temperature sensor input 3 |
| Pin 41 | TSENSE4 — Temperature sensor input 4 |
| Pin 42 | EIS_OUT — EIS excitation output |
| Pin 43 | EIS_IN — EIS measurement input |
| Pin 44 | TEST — Test mode (factory only) |
| Pin 45 | NC — Not connected |
| Pin 46 | HV — High-voltage supply input |
| Pin 47 | BST_NC — Not connected |
| Pin 48 | EP — Exposed thermal pad (connect to AGND) |
Typical Applications
BQ79881-Q1 is suitable for 6 applications: EV/HEV Battery Management System, Battery Junction Box (BJB) Pack Monitor, Pack-Level EIS Battery Health Diagnostics, Stationary Energy Storage Systems (ESS), Industrial Battery Backup Systems, Hybrid Electric Vehicle (HEV) Battery Pack.
EV/HEV Battery Management System
The BQ79881-Q1 is the core pack-level monitor in EV/HEV high-voltage BMS designs, providing ASIL-D HV measurement accuracy (<0.4%) per ISO 26262. Its integrated UIR function continuously verifies HV isolation between the battery pack and chassis, detecting creepage or breakdown faults that could create a chassis-shock hazard. Combined with a BQ79718BQPAPRQ1 cell monitor, it enables a complete 18S-32S BMS for 400V and 800V architectures.
Recommended
Battery Junction Box (BJB) Pack Monitor
In automotive battery junction boxes, the BQ79881-Q1 acts as the central UIR sensor, measuring pack voltage, current (via external shunt), and performing insulation resistance tests. The 0us internal VI sync enables simultaneous voltage/current sampling for accurate coulomb counting, while the 5us VI sync with cell monitors preserves pack-level synchronization. The LQFP-48 EP package handles underbody thermal loads during high-current EV operation.
Recommended
Pack-Level EIS Battery Health Diagnostics
The BQ79881-Q1's integrated EIS engine performs in-situ AC impedance spectroscopy on the entire battery pack, enabling state-of-health, state-of-charge, and aging characterization. Unlike discrete EIS implementations requiring external signal generators and ADCs, the integrated engine reduces BOM cost by 30-50% and PCB area. Pack-level EIS detects cell-to-cell aging variations and provides thermal-runaway precursors 24-48 hours before critical events.
Recommended
Stationary Energy Storage Systems (ESS)
For grid-tied and commercial battery energy storage, the BQ79881-Q1 provides automotive-grade reliability for high-voltage battery cabinets. The ASIL-D-derived functional safety architecture and insulation resistance monitoring protect service technicians during maintenance. Pack-level EIS enables remote battery health monitoring over the asset's 15-20 year lifetime, reducing on-site inspection frequency and total-cost-of-ownership for ESS operators.
Recommended
Industrial Battery Backup Systems
Industrial UPS and battery backup systems benefit from the BQ79881-Q1's automotive-grade robustness and ASIL-D HV measurement capability. The integrated insulation resistance test ensures compliance with industrial safety standards for HV battery cabinets, while pack-level EIS provides early warning of battery degradation before catastrophic failure. The AEC-Q100 qualification delivers automotive-grade reliability for industrial environments requiring 10+ year operational lifetimes.
Recommended
Hybrid Electric Vehicle (HEV) Battery Pack
In HEV applications with 48V mild-hybrid architectures, the BQ79881-Q1 provides ASIL-D insulation monitoring and pack-level EIS for the 48V battery pack. The 0.3-5V single-ended measurement range covers typical HEV cell voltages, and the 5us VI sync maintains synchronization with the 48V cell monitor. The integrated UIR function detects isolation faults in the 48V system that could affect low-voltage ECU networks sharing chassis ground.
Recommended
Recommended Products Summary
Engineering reference data for BQ79881-Q1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BQ79826Z-Q1 | BQ79616-Q1 | BQ79631-Q1 | BQ79600-Q1 | BQ79617-Q1 |
|---|---|---|---|---|---|---|
| Package | LQFP-48 (7x7 mm) with EP | LQFP-48 (7x7 mm) - same | LQFP-48 (7x7 mm) - same | LQFP-48 (7x7 mm) - same | LQFP-48 (7x7 mm) - same | LQFP-48 (7x7 mm) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Function | UIR + Pack-Level EIS | 26S Cell Monitor + Smart EIS Engine | 16S Cell Monitor (no EIS/UIR) | 32S Cell Monitor | SPI/UART Comms MCU | 17S Cell Monitor |
| UIR (Insulation Resistance) | Yes (integrated) | No | No | No | No | No |
| EIS Engine | Pack-level EIS (integrated) | Smart EIS Engine (per-cell) | No | No | No | No |
| Cell Monitor Channels | Pack-level (no per-cell) | 26S | 16S | 32S | 0 (comms MCU) | 17S |
| Automotive Grade | AEC-Q100 (ASIL-D) | AEC-Q100 | AEC-Q100 | AEC-Q100 | AEC-Q100 | AEC-Q100 |
Key Differentiators
- Integrated pack-level EIS engine (vs BQ79616-Q1)
- Integrated UIR (insulation resistance) monitoring (vs BQ79826Z-Q1)
- ASIL-D HV measurement accuracy <0.4% (vs BQ79718BQPAPRQ1)
- 0us internal VI sync (vs BQ79631-Q1)
Design Notes
The LQFP-48 package with exposed thermal pad (EP) MUST be soldered to a copper pour of at least 1 square inch on the top and inner PCB layers to keep junction temperature within the -40C to +125C automotive range. During active EIS measurements the IC can dissipate 0.5-1.5W, and without proper thermal design, junction temperature will exceed safe limits in underbody EV environments where ambient can reach 85C.
The shunt resistor for current sensing must be placed within 50mm of the SRP/SRN inputs to minimize ground-loop noise. Use a Kelvin connection (4-wire) to the shunt for accurate current measurement. The HV isolation barrier between PACKP/PACKN and low-voltage signals must comply with IEC 60664 creepage/clearance requirements - typically 8mm minimum for 800V automotive systems.
Do not bypass the AVSS/AVDD decoupling capacitors - place 100nF and 10uF ceramic capacitors within 5mm of the supply pins. The internal reference (REF pin) requires a low-ESR 100nF bypass capacitor for ADC accuracy. Do not connect the TEST pin to any signal in production designs, as it activates factory test modes. Always use the EIS_OUT through a series resistor to limit inrush current during AC excitation.
The SPI/UART communication lines to the host MCU should be routed with controlled impedance (50 ohm) and length-matched within 5mm if using SPI at >1 MHz. Add 33 ohm series damping resistors at the driver outputs to reduce ringing. For daisy-chained BQ796xx configurations, use TI's recommended daisy-chain topology with twisted-pair or shielded cabling to minimize EMI susceptibility in automotive environments.
Compliance Information
AEC-Q100 qualified per TI product page. ASIL-D capable per ISO 26262 for HV measurement functional safety. RoHS and REACH compliant. Halogen-free status not explicitly stated in provided data.
