MAX712 MAX713

MAX712/MAX713 NiCd/NiMH Battery Fast-Charge Controllers

Overview

The MAX712 and MAX713 are advanced fast-charge controllers designed for Nickel Metal Hydride (NiMH) and Nickel Cadmium (NiCd) batteries. These components efficiently manage the charging process from a DC source, requiring a voltage at least 1.5V higher than the maximum battery voltage. They support charging for 1 to 16 series-connected cells at rates up to 4C. The devices incorporate a sophisticated voltage-slope detecting analog-to-digital converter, a timer, and a temperature window comparator to ensure safe and optimal charging.

Key functionalities include automatic switching from fast charge to trickle charge, linear mode power control, and the ability to supply the battery's load while charging. With a minimal 5µA (max) drain on the battery when not charging, these controllers are ideal for power-sensitive applications. Additionally, they feature a built-in 5V shunt regulator to power external logic circuits.

Features

• Fast-Charge NiMH or NiCd Batteries: Supports rapid charging for both NiMH and NiCd battery chemistries.
• Voltage Slope, Temperature, and Timer Fast-Charge Cutoff: Utilizes multiple safety mechanisms to terminate fast charging based on voltage slope, temperature thresholds, and timer expiration.
• Charge 1 to 16 Series Cells: Flexible configuration for charging single or multiple series-connected cells.
• Supply Battery’s Load While Charging (Linear Mode): Maintains power delivery to the load even during the charging process.
• Fast Charge from C/4 to 4C Rate: Wide range of fast-charge rates to accommodate different battery capacities.
• C/16 Trickle-Charge Rate: Automatically switches to trickle charging after fast charge completion to maintain battery health.
• Automatically Switch from Fast to Trickle Charge: Ensures seamless transition between charging modes without user intervention.
• Linear Mode Power Control: Provides efficient power management during charging.
• 5µA (max) Drain on Battery when Not Charging: Minimizes power loss when the charger is idle.
• 5V Shunt Regulator Powers External Logic: Includes a built-in regulator for powering additional circuitry.

Applications

The MAX712 and MAX713 are versatile components suitable for a wide range of applications, including:

• Portable Electronics: Ideal for handheld devices such as digital cameras, portable media players, and medical devices.
• Power Tools: Provides efficient charging for cordless drills, saws, and other battery-operated tools.
• Emergency Backup Systems: Ensures reliable charging for backup power solutions in critical applications.
• Consumer Electronics: Suitable for rechargeable battery packs in toys, remote controls, and other consumer gadgets.
• Industrial Equipment: Used in industrial-grade battery charging systems for machinery and instrumentation.

Electrical Characteristics

The following table summarizes the key electrical characteristics of the MAX712/MAX713:

• Input Voltage Range: DC source must be at least 1.5V higher than the maximum battery voltage.
• Fast-Charge Rate: Adjustable from C/4 to 4C, depending on battery specifications.
• Trickle-Charge Rate: Fixed at C/16 to maintain battery charge without overcharging.
• Quiescent Current: Maximum of 5µA when not actively charging.
• Shunt Regulator Output: 5V for powering external logic circuits.
• Operating Temperature Range: 0°C to +70°C for commercial-grade versions.

Package Information

The MAX712 and MAX713 are available in multiple package options to suit different application requirements:

• MAX712CPE: 16-pin Plastic DIP (Dual In-line Package) for through-hole mounting.
• MAX712CSE: 16-pin Narrow SO (Small Outline) package for surface-mount applications.
• MAX712C/D: Dice form for custom integration (contact factory for specifications).

For military-grade applications or additional package options, please contact the factory for availability and processing details.

Typical Operating Circuit

The typical operating circuit for the MAX712/MAX713 includes the following components:

• DC Input: Provided by a wall cube adapter or similar DC source.
• External Transistor (Q1): Such as a 2N6109, to handle the charging current.
• Diode (D1): 1N4001 for reverse polarity protection.
• Sense Resistor (RSENSE): To monitor charging current.
• Capacitors (C1-C4): For filtering and stability, including 10µF and 0.01µF values.
• Resistors (R1-R4): For setting thresholds and feedback, including 150Ω, 68kΩ, and 22kΩ values.

Pin Configuration

The 16-pin DIP/SO package pinout is as follows:

• Pin 1 (REF): Reference voltage output.
• Pin 2 (V+): Positive supply voltage input.
• Pin 3 (DRV): Drive output for external transistor.
• Pin 4 (GND): Ground connection.
• Pin 5 (BATT-): Negative battery terminal connection.
• Pin 6 (CC): Charge control input.
• Pins 7-8 (PGM3, PGM2): Programming inputs for charge rate and cell count.
• Pin 9 (VLIMIT): Voltage limit setting.
• Pin 10 (BATT+): Positive battery terminal connection.
• Pins 11-12 (PGM0, PGM1): Additional programming inputs.
• Pins 13-14 (THI, TLO): Temperature threshold inputs for high and low limits.
• Pin 15 (TEMP): Temperature sensor input.
• Pin 16 (FASTCHG): Fast-charge status output.

Conclusion

The MAX712 and MAX713 are robust and flexible fast-charge controllers for NiMH and NiCd batteries, offering a comprehensive suite of features to ensure safe and efficient charging. With support for up to 16 series cells, multiple charge termination methods, and minimal standby power consumption, these devices are well-suited for a variety of portable and industrial applications. The availability of different package options further enhances their versatility, making them a reliable choice for designers seeking high-performance battery management solutions.