Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - battery management Charge management NiMH TDFN 10 EP (3x4) Surface-mount

General Description

The DS2710 is ideal for in-system charging of single-cell

nickel metal hydride (NiMH) cells for low-current

portable applications. Inputs to the DS2710 include USB

voltage sources and 5V regulated adapters.

Temperature, voltage, and charge time are monitored to

provide proper fast-charging control algorithms for

single-cell NiMH or nickel cadmium (NiCd) batteries.

The DS2710 includes battery tests to detect defective or

inappropriate cells such as alkaline primary batteries.

Applications

Small Rechargeable Devices

Voice Recorders

Cordless Mouse

Battery-Powered Toys

Features

♦ Charges Single-Cell NiMH Cells

♦ Switch-Mode Topologies Supported by Hysteretic

Control Technique

♦ Precharges Deeply Depleted Cells

♦ Fast-Charges NiMH with -ΔV Termination

Sensitivity of 2mV (typ)

♦ Monitors Voltage, Temperature, and Time for

Safety and Secondary Termination

♦ Regulates Charge Current

♦ Designed for External pMOS

♦ Rail-to-Rail MOSFET Driver

♦ Tiny 10-Pin TDFN Package (3mm x 4mm)

DS2710

Single-Cell NiMH Charger

________________________________________________________________

Maxim Integrated Products

DS2710

110

VP1V

3 8 VN0V

2 9 VN1CS

4 7 TMRTHM

5 6 CTESTSTATUS

TDFN

(3mm

4mm)

TOP VIEW

*EP

*EXPOSED PAD.

Pin Configuration

Ordering Information

DS2710

VP1

THM

VN0 VN1

SENSE

CHARGE

SOURCE

NiMH

CELL

GROUND

Typical Operating Circuit

Rev 0; 4/08

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Denotes a lead(Pb)-free/RoHS-compliant package.

T&R = Tape and reel.

EP = Exposed pad.

PART PIN-PACKAGE

DS2710G+ 10 TDFN-EP*

DS2710G+T&R 10 TDFN-EP*

Summary of content (12 pages)

PAGE 1
Rev 0; 4/08 Single-Cell NiMH Charger The DS2710 is ideal for in-system charging of single-cell nickel metal hydride (NiMH) cells for low-current portable applications. Inputs to the DS2710 include USB voltage sources and 5V regulated adapters. Temperature, voltage, and charge time are monitored to provide proper fast-charging control algorithms for single-cell NiMH or nickel cadmium (NiCd) batteries.
PAGE 2
DS2710 Single-Cell NiMH Charger ABSOLUTE MAXIMUM RATINGS Voltage Range on All Pins Relative to VSS ............-0.3V to +6.0V Continuous Source/Sink Current CS ...................................20mA Continuous Source Current STATUS ..................................10mA Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-55°C to +125°C Soldering Temperature...........................Refer to the IPC/JEDEC J-STD-020 Specification.
PAGE 3
Single-Cell NiMH Charger (4.0V ≤ VDD ≤ 5.5V, TA = -20°C to +70°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS Cold Temperature Detect Threshold VTHM-MIN (Notes 1, 5, 8) Hot Temperature No-Start Threshold VTHM-MAX (Notes 1, 5, 8) Hot Temperature Safety Shutdown Threshold VTHM-STOP (Notes 1, 5, 8) SUSPEND Current Threshold I SUSPEND Reverse-Leakage Current, VP1 Impedance-Voltage Test Range TYP MAX 0.73 0.30 0.33 (Note 9) 1.0 0.36 VDD VDD 0.1 0.
PAGE 4
Single-Cell NiMH Charger DS2710 Pin Description PIN NAME 1 VSS Device Ground. Connects directly to the negative terminal of the charge source. FUNCTION 2 CS Charge Source. Feedback control for switching circuitry. 3 VDD Power-Supply Input. Connects to the positive terminal of the charge source through a decoupling network. 4 THM Thermistor Input. Connects to a thermistor located near the cell and a resistor-divider from the VDD pin. 5 STATUS 6 CTEST 7 TMR Status Output.
PAGE 5
Single-Cell NiMH Charger Charge Algorithm Overview The DS2710 controls switch-mode topology charging of a single NiMH cell from a voltage-regulated charge source. The IC is reset in one of two ways: with the application of power to the DS2710 or after exiting SUSPEND state. Once one of these conditions occurs, the DS2710 enters the PRESENCE state and waits for a cell to be inserted before starting a charge cycle.
PAGE 6
DS2710 Single-Cell NiMH Charger RTMR > RSUSPEND (ASYNCHRONOUSLY FROM ANYWHERE) SUSPEND RTMR < RSUSPEND CS = INACTIVE STATUS = LOW VDD < VUVLO - VUHYS (ASYNCHRONOUSLY FROM ANYWHERE) PRESENCE VDD > VUVLO (3.5V) POR CS = INACTIVE STATUS = LOW CS = INACTIVE PRECHARGE t < tPCHG AND VCELL < 1.0V VCELL < VMAX-OPEN CS = ACTIVE 25% DF STATUS = 1Hz TOGGLE t > tPCHG OR T > +50°C OR VCELL > VMAX* VCELL > 1.0V AND t < tPCHG AND T < +50°C VCELL > 1.75V OR T < 0°C OR T > +45°C VCELL > 1.
PAGE 7
Single-Cell NiMH Charger the cell voltage is greater than VMAX-CHARGE during the 25% of time when charge current is applied or VMAX-OPEN during the remaining time, TOP-OFF is exited early and the DS2710 goes to FAULT. CELL TEST MAINTENANCE CELL TEST is performed once every 31s during FASTCHARGE to determine if charging is complete. During CELL TEST, the CS output is held high to prevent charging. The cell’s voltage is measured and compared against prior readings.
PAGE 8
Charge-Current Regulation The DS2710 regulates charge current by maintaining a constant average voltage across an external sense resistor connected between the VN1 and VN0 pins. VN1 and VN0 drive an internal comparator in the DS2710 to switch the CS output ON and OFF to drive a regulating pnp bipolar or a pMOS transistor. Hysteresis on the comparator input provides noise rejection.
PAGE 9
Single-Cell NiMH Charger Used with a 10kΩ resistor, the Semitec 103AT-2 provides approximately 0.9% full scale-per-degree sensitivity. Figure 4 shows this linearity curve. The left axis is the ratio of the sensed voltage to the divider’s input voltage (VDD). Charge-Status Output The DS2710 indicates the state of charge and the charge results on the STATUS output pin. When no cell is present, the output is driven to a logic-low. Any LED attached to the STATUS pin is off.
PAGE 10
DS2710 Single-Cell NiMH Charger Timeout Selection Application Circuit FAST-CHARGE state normally operates until -ΔV termination. In the event that termination does not occur correctly, a safety timeout is required. This timeout is set by an external resistor on the TMR pin to VSS and provides secondary protection against significant overcharging.
PAGE 11
Single-Cell NiMH Charger DS2710 R3 270kΩ Q1 ZXM62P02E6 +5V (USB+) R1 150Ω L1 15μH SISCDRH74M-150R C2 10μF CERAMIC C3 10μF CERAMIC D2 1W B340A-13 SCHOTTKY R6 1kΩ CS VP1 VDD 1S NiMH CELL R4 10kΩ THM C1 1μF VN1 DS2710 R9 0.1Ω 1W STATUS RT1 103AT-2 GROUND (USB-) VN0 TMR R2 1kΩ D1 GREEN SMA CTEST R7 100kΩ VSS R8 47kΩ Figure 5.
PAGE 12
DS2710 Single-Cell NiMH Charger CONTROL RGATE LSWITCH QSWITCH CHARGE SOURCE SIDE LOOP1 CIN DSWITCH LOOP2 COUT BATTERY SIDE LOOP AREAS MINIMIZED CHARGE SOURCE SIDE CI RG DS QS BATTERY SIDE CO LS BACKSIDE GROUND PLANE CONTROL Figure 6. Switching Circuit with Example Layout SENSE+ SENSE- SENSE+ SENSE- SENSE TRACES RUN CLOSE TOGETHER TO MINIMIZE LOOP INDUCTANCE PROPER KELVIN CONNECTION AT SENSE RESISTOR RSNS CHARGE SOURCE- BATTERY- CHARGE SOURCE- RSNS BATTERY- Figure 7.