Precision Resistor Dividers Extend HV Battery Life
Texas Instruments' RES60A-Q1 integrated, 1.4-kV, single-chip thin-film resistor divider helps extend the lifetime of hybrid, electric-vehicle, and battery energy storage system (BESS) batteries when incorporated into battery-management systems (BMS). Today’s BMS designs typically use long chains of discrete resistors whose drifting tolerance degrades voltage-sensing accuracy over time, causing state-of-charge and battery state-of-health estimation errors.
The RES60A-Q1 is a matched resistive divider (Fig. 1) implemented in thin-film SiCr with the company's modern, high-performance, analog wafer process. A high quality SiO2 insulative layer encapsulates the resistors and enables usage at extremely high voltages, up to 1,400 V DC for sustained operation or 4,000 V DC for HiPOT testing (60s). The device has a nominal input resistance of RHV = 12.5 MΩ, and is available in several nominal ratios to meet a wide array of system needs.
The RES60A-Q1 eliminates the need for lengthy discrete resistor chains with a single-chip, high-voltage resistor divider. It achieves 0.1% initial ratiometric precision with a maximum of 0.2% ratiometric drift over a 10-year lifetime, providing accurate and consistent monitoring of the battery pack.
Such precision is maintained over the specified temperature range and aging, with a cumulative drift of only ±0.2% (max). Therefore, the lifetime tolerance of an uncalibrated RES60A-Q1 remains within a ±0.3% (max) envelope. Ratios of 1,000:1, 145:1, 210:1, 310:1, 315:1, 410:1, 500:1, 510:1, and 610:1 are available.
The RES60A-Q1 is automotive qualified under AEC-Q200 temperature grade 1, with a specified temperature range from –40 to +125°C. It features a nominal input resistance of 12.5 MΩ, and withstands temperature and 4-kV DC HiPOT (60s) tests to maintain accuracy, helping engineers meet strict high-voltage design requirements.
Features
- AEC-Q200 qualified for automotive applications
- Temperature grade 1: –40°C to +125°C
- High voltage rating: Survives 3+ HiPOT tests at 4,000 V DC (60s), 1,700-V DC creepage and clearance support between HVIN and LVIN (IEC-61010 PD 2)
- High dc precision with low shift and drift
- Initial ratio matching precision: ±0.1% (max)
- Low drift: ±1 ppm/°C (typ)
- Accurate ±0.2% across aging and temperature
- Low thermal noise (1 kHz) thin-film resistors: 30 nV/√Hz (210:1 ratio), 2 5nV/√Hz (310:1 ratio), 22 nV/√Hz (410:1 ratio), 20 nV/√Hz (500:1 ratio), 18 nV/√Hz (610:1 ratio), 14 nV/√Hz (1,000:1 ratio)
Applications
- High-voltage bus and battery voltage monitoring
- HEV/EV battery management system (BMS)
- HEV/EV DC-DC converter
- HEV/EV onboard charger (OBC)
- HEV/EV inverter and motor control
Packaging and Design Considerations
The device is offered in an 8-pin SOIC package, with nominal body size (7.5 × 5.85 mm), and features creepage and clearance distances of at least 8.5 mm between the high- and low-voltage pins.
The RES60 evaluation module (EVM) is designed to help users easily evaluate and test the operation and functionality of the RES60 device in the typical configuration, (Fig. 2). The EVM is configured as a resistor divider followed by an operational-amplifier buffer. The EVM operates on a split-supply from ±0.9 to ±2.75 V. The default configuration of the EVM uses a resistor divider of 500:1.
For more details on the application of high-voltage resistor dividers, check out Texas Instruments' contributed article on them in our Automotive Electrification (BMS) eBook, downloadable here.
At the time of this writing, the RES11A40DDFR is in distributor stock and priced at around $1.08 for 1k pieces. The RES60A-Q1 Evaluation Board is available for about $99.
For Electronic Design readers' convenience, the RES60A-Q1 datasheet is provided below, though it would be wise to obtain the latest revision and other RES60-A1 design resources from TI before starting a design.
