Analog Devices Inc./Maxim Integrated DS2703U+T&R

Overview

DS2703U+T&R from Maxim Integrated is a 1-Wire SHA-1 battery pack authentication IC designed for secure challenge-response verification in removable Li-ion battery systems. It features a 64-bit ROM ID, on-chip 64-bit secret key storage, 160-bit MAC generation, thermistor multiplexing via THM pin, and operates from 2.7V to 5.5V VPULLUP. Used in mobile handsets and portable computing to prevent counterfeit battery use.

For engineers reviewing the DS2703U+T&R datasheet, DS2703U+T&R pinout, DS2703U+T&R application, or DS2703U+T&R equivalent, key selection criteria include 1-Wire overdrive timing support (143kbps), thermistor mux activation latency (≤15μs), SHA-1 computation time (15ms), standby current (≤2.5μA), and μMAX-8 package compatibility with space-constrained battery pack PCB layouts.

Technical Context

The DS2703U+T&R implements FIPS-180-1/180-2 and ISO/IEC 10118-3 compliant SHA-1 hashing for cryptographic authentication, processing a 512-bit message block containing 64-bit secret, 64-bit challenge, and fixed constants (or ROM ID). Its 1-Wire interface supports both standard (16μs slot) and overdrive (6μs slot) timing modes, with internal HV detection enabling EEPROM programming at 14.5–15.0V on DQ.

Four distinct operating modes-communication, computation, programming, and thermistor access-are managed via command-driven state transitions. Thermistor mode disconnects internal DQ loading and drives THM to VSS, enabling direct thermistor impedance measurement on the DQ line without additional pack contacts.

Key Specifications

Pinout & Package

DS2703U+T&R is housed in an 8-pin μMAX® package (3mm × 3mm, 0.8mm height), lead-free, with exposed paddle for thermal dissipation. Pin 1 is THM; Pin 3 is DQ (open-drain 1-Wire I/O); Pin 4 is VB (hold-up bypass requiring 0.22μF capacitor to VSS); Pins 5–8 are no-connect.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery authentication applications.

Compared with DS2703U+T&R, DS2705G+T&R offers smaller footprint but removes thermistor integration, increasing BOM and assembly cost; BQ26200PW mandates interface and firmware redesign, making it unsuitable for drop-in replacement in 1-Wire-based legacy platforms.

Availability

DS2703U+T&R is available at Aetrix Electronics and suitable for 2.5G/3G wireless handsets, PDAs, and handheld computers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for DS2703U+T&R includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and digital ICs for industrial, communications, computing, and consumer applications.

The DS2703U+T&R belongs to Maxim's battery fuel gauge and authentication product line, engineered specifically to provide cryptographic assurance and thermistor integration for Li-ion battery packs in portable electronics.

FAQ

What is the primary function of the DS2703U+T&R in a battery pack?

The DS2703U+T&R serves as a cryptographic authenticator that verifies battery legitimacy using SHA-1 challenge-response authentication. It stores a unique 64-bit ROM ID and 64-bit secret key, computes a 160-bit MAC upon host request, and supports thermistor multiplexing on the DQ line. The DS2703U+T&R enables host systems to reject counterfeit or degraded batteries before enabling charge or power delivery.

Does the DS2703U+T&R require an external power supply?

No, the DS2703U+T&R operates in parasitic power mode directly from the 1-Wire DQ line using a pullup resistor, with VPULLUP ranging from 2.7V to 5.5V. An external 0.22μF capacitor on the VB pin provides hold-up energy during DQ low periods and thermistor measurements. No separate VDD connection is needed-the DS2703U+T&R draws current only during active communication or computation.

How does the thermistor multiplexing feature work on the DS2703U+T&R?

The DS2703U+T&R activates thermistor mode via the 0xA9 (Activate Thermistor) command, internally driving the THM pin to VSS and disconnecting DQ from internal circuitry. This allows the external thermistor (connected between DQ and THM) to form a voltage divider with the host's weak pullup, enabling temperature measurement using the host's ADC. The DS2703U+T&R remains in this mode until the VB capacitor discharges-typically 200–1000ms depending on VPULLUP.

Can the secret key in the DS2703U+T&R be updated after initial programming?

Yes, the DS2703U+T&R supports dynamic secret key updates using LOAD SECRET (0x5A) or COMPUTE NEXT SECRET (0x30/0x33) commands, followed by a 14.5–15.0V programming pulse on DQ. Once LOCK SECRET (0x6A) is executed and programmed, the secret becomes read-only. The DS2703U+T&R retains the locked secret across power cycles and supports EEPROM write endurance of at least 1000 cycles.

What 1-Wire timing modes does the DS2703U+T&R support, and how are they selected?

The DS2703U+T&R supports both standard (16kbps, 60–120μs time slots) and overdrive (143kbps, 6–16μs time slots) 1-Wire modes. Mode selection is controlled by the SET OVERDRIVE (0x8B) or CLEAR OVERDRIVE (0x8D) command, with the setting stored in EEPROM for retention across power cycles. The DS2703U+T&R automatically uses the configured mode after reset-no host reinitialization is required.