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DESCRIPTION

The DS2715 is well suited for cost-sensitive charger

applications where the battery is either internal or in a

unique battery pack. It has been optimized for safe

reliable charging of 1 to10 NiMH cells in series. The

DS2715 has an internal gain block that can be

selected as either a comparator or transconductance

amplifier for charge current regulation. The DS2715 is

configurable as a switched DC charger, a linear

current regulator, or a switchmode current source.

The DS2715 pre-conditions severely depleted cells

are pre-conditioned before entering full charge mode.

The DS2715 terminates full charge using the dT/dt

technique. It requires an external thermistor for dT/dt

detection. Over-temperature, under-temperature, and

over-voltage detection prevents charging under

unsafe environmental conditions. A user selectable

charge timer allows charge rates from 0.15C to 2C.

Fast-charge, top-off and charge done modes are

included for highly reliable, safe charging of NiMH

cells. Discharge mode allows the DS2715 to enter a

low power sleep state while the cell pack is being

discharged.

FEATURES

§ Charges 1 to 10 NiMH Cells

§ Fast Charges up to a 2C Rate

§ Pre-Charge and Top-Off Charge Modes Help Cell

Conditioning

§ Load Detection Allows the DS2715 to Enter Low

Power Sleep Mode (Less than 10µA) while the

Cell Pack is Discharged

§ dT/dt Charge Termination Eliminates Cell Charge

Stress

§ Monitors Voltage, Temperature, and Time for

Safety and Secondary Termination

§ Regulates Current through Either Linear Control

or Switch-Mode Control

§ LED Outputs Display Charge State

§ Small 16-Pin SO Package

APPLICATIONS

Portable DVD Players

Portable Television Sets

Handheld Gaming

Test Equipment

Handheld POS Terminals

PIN CONFIGURATION

VP2

VP1

CC1

CC2

LED1

VSS

LED2

CSOUT

VN1

VN0

THM2

THM1

VDD

TMR

CTST

DMSEL

Table 1.

ORDERING INFORMATION

+ Denotes lead-free package.

OPERATIONAL DIAGRAM

Vch

Vbatt

THM

Vdd

Sense

DS2715

CHARGE

SOURCE/LOAD

GROUND

Divide by n

n Cells

PART MARKING PIN-PACKAGE

DS2715Z+

DS2715+

16 SO

DS2715Z+T&R DS2715+ 16 SO Tape-and-Reel

DS2715

NiMH Battery Pack Charge Controlle

www.maxim-ic.com

See Table 1 for Ordering Information.

16 SO

BIAS

LED1

LED2

CTG

BATT

THM

SNS-

SNS+

DIV

MODE

Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device

be simultaneousl

available throu

h various sales channels. For information about device errata

click here: www.maxim

ic.com/errata.

Summary of content (12 pages)

PAGE 1
DS2715 NiMH Battery Pack Charge Controller www.maxim-ic.com DESCRIPTION PIN CONFIGURATION The DS2715 is well suited for cost-sensitive charger applications where the battery is either internal or in a unique battery pack. It has been optimized for safe reliable charging of 1 to10 NiMH cells in series. The DS2715 has an internal gain block that can be selected as either a comparator or transconductance amplifier for charge current regulation.
PAGE 2
DS2715: NiMH Cell Pack Charge Controller ABSOLUTE MAXIMUM RATINGS* Voltage on VDD and VCH Pins with Respect to VSS Voltage on LED1 and LED2 Pins Voltage on SNSVoltage on CBIAS Voltage on all Other Pins Continuous Sink Current VCH, LED1, and LED2 Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +18V -0.3V to +18V -0.3V to +0.3V -0.3V to 6V -0.
PAGE 3
DS2715: NiMH Cell Pack Charge Controller AC ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL UVLO Debounce Time tUVLO Current Sense Comparator Propagation Delay tCOMP (4.5V £ VDD £ 16.5V, TA = 0°C to +70°C, unless otherwise noted.
PAGE 4
DS2715: NiMH Cell Pack Charge Controller Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Voltages relative to VSS. Does not include current through VCH, RT, and DIV pins. Below this voltage no I/O pins are active. Does not include tolerance of RT resistor. VBIAS and resistor tolerances must be added to determine actual threshold. Specified temperature thresholds are only valid if recommended thermistor types are used. Specification is guaranteed by design.
PAGE 5
DS2715: NiMH Cell Pack Charge Controller Figure 1. BLOCK DIAGRAM DS2715 Cbias VDD Pwr HV VUVLO Disable during discharge Div R E F Regulator Ref LED2 A D C Fast Charge Exit on Full Or Timeout HV THM State Machine Pre-Charge Low Cells HV Th UVLO Oscillator LED1 Vbatt M U X Disch. Detect @-0.
PAGE 6
DS2715: NiMH Cell Pack Charge Controller Figure 2. STATE DIAGRAM DS2715 State Diagram Discharge Latch Set VDD < V UVLO-VUVLO-HYS (asynchronously from anywhere) Reset Vch = Hi-Z LED Hi-Z= No Battery Vbatt>1.65 Vref = 0.033V LED1 = Charging 30 min PCtimeout Vbatt < 1V Vbatt < 1.55V AND 0C < T < 45C Vbatt > 1.
PAGE 7
DS2715: NiMH Cell Pack Charge Controller DETAILED DESCRIPTION Charge Cycle Overview The DS2715 regulates the charge of up to 10 NiMH cells in a series configuration. With the mode select pin the DS2715 can be configured to regulate either as an error amplifier in linear mode or as a comparator in switched mode. A charge cycle begins in one of two ways: with the application of power to the DS2715 with cell pack already inserted or with the detection of cell insertion after power-up.
PAGE 8
DS2715: NiMH Cell Pack Charge Controller DONE state. If at any time during fast charge the voltage on VBATT exceeds 1.65V (VOPEN), the DS2715 determines that the cell pack has been removed and returns to the PRESENCE state. Top-Off In top-off mode, the DS2715 regulates the voltage across the sense resistor to -33mV (VTO) in linear mode or 29mV (VTO - 0.5 x VHYS-TO) in comparator mode. LED1 indicates the cell pack is being charged.
PAGE 9
DS2715: NiMH Cell Pack Charge Controller Figure 3. TYPICAL APPLICATION CIRCUIT FOR A 3-CELL STACK LOAD CR2 R1 LED2 LED1 CR1 +9VDC C1 10 uF R2 470 R3 1K R12 1K C3 10 uF R9 47 100 Q1 IRF9Z24 LED1 Vch LED2 Vbatt C4 0.1 uF Div Mode SNS+ Cbias 5.6V R4 100 U1 DS2715 Vdd Rt R6 68K VR1 R7 10K R5 200K R8 100K VSS THM VSS CTG SNSR11 47 R10 0.
PAGE 10
DS2715: NiMH Cell Pack Charge Controller CURRENT REGULATION Three basic modes of charging operation are supported by the DS2715: Offline switching through an optocoupler, linear regulation, and DC input switched mode. The DC Switched method requires a currrent-limited power source. Mode of operation is selected through the Mode pin. Connecting the Mode pin to VSS configures the analog block as a transconductance amplifier for linear mode of operation.
PAGE 11
DS2715: NiMH Cell Pack Charge Controller TEMPERATURE SENSE Accurate temperature sensing is needed to determine end of charge by dT/dt and to detect over temperature fault conditions. Connecting an external 10kW NTC thermistor between THM and VSS, and a 10kW bias resistor between Div and THM allows the DS2715 to sense temperature. To sense the temperature of the cell pack, locate the thermistor close to the body of a cell, preferably in the middle of the cell pack.
PAGE 12
DS2715: NiMH Cell Pack Charge Controller LED1 and LED2 Outputs Open-drain outputs LED1 and LED2 pull low to indicate charge status. When inactive, the outputs are high impedance. LED1 displays the state of charge and LED2 displays the charge results. The LED1 pin drives low in a 1Hz, 50% duty cycle “blink” pattern to indicate cells are charging. LED2 drives low with 100% duty cycle to signal a successful charge completion or blinks at 4Hz, 50% duty cycle to signal a charging fault has occurred.