Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - battery management Charge management NiMH SOIC 16 Surface-mount

AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

For pricing, delivery, and

ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

DESCRIPTION

The DS2715 is well suited for cost-sensitive charger

applications where the battery pack is either internal

or external to the application. It has been optimized for

safe and reliable charging of 1 to 10 NiMH cells in

series. The internal gain block can be selected as

either a comparator or transconductance amplifier for

charge current regulation. This makes the DS2715

configurable as a switched DC charger, a linear

current regulator, or a switchmode current source.

The DS2715 pre-conditions severely depleted cells

before entering full charge mode. It terminates full

charge using the dT/dt technique, which requires an

external sensing thermistor. Over-temperature, under-

temperature, and over-voltage detection prevents

charging under unsafe conditions. A user selectable

charge timer allows charge rates from 0.167C to 2C.

FAST-CHARGE, TOPOFF and 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-CHARGE at up to a 2C Rate

 PRECHARGE and TOPOFF 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 Output Displays Charge State

 Small 16-Pin SO Package

APPLICATIONS

Portable DVD Players

Portable Television Sets

Handheld Gaming

Test Equipment

Handheld POS Terminals

PIN CONFIGURATION

Table 1.

ORDERING INFORMATION

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

T&R = Tape and reel.

OPERATIONAL DIAGRAM

PART MARKING PIN-PACKAGE

DS2715Z+

D2715

16 SO

DS2715Z+T&R D2715 16 SO

DS2715BZ+ D2715B 16 SO

DS2715BZ+T&R D2715B 16 SO

DS2715

NiMH Battery Pack Charge Controlle

www.maxim-ic.com

See Table 1 for Ordering Information.

16 SO

BIAS

LED1

DNC

CTG

BATT

THM

SNS-

SNS+

DIV

MODE

19-4592; 4/09

Summary of content (17 pages)

PAGE 1
LE AVAILAB DS2715 NiMH Battery Pack Charge Controller www.maxim-ic.com DESCRIPTION The DS2715 is well suited for cost-sensitive charger applications where the battery pack is either internal or external to the application. It has been optimized for safe and reliable charging of 1 to 10 NiMH cells in series. The internal gain block can be selected as either a comparator or transconductance amplifier for charge current regulation.
PAGE 2
DS2715: NiMH Battery Pack Charge Controller ABSOLUTE MAXIMUM RATINGS* Voltage on VDD and VCH Pins with Respect to VSS Voltage on LED1 Pin Voltage on SNSVoltage on CBIAS Voltage on all Other Pins Continuous Sink Current VCH and LED1 Operating Temperature Range Storage Temperature Range Soldering Temperature Human Body Model (HBM) ESD Limit of VCH Pin HBM ESD Limit of all Other Pins -0.3V to +18V -0.3V to +18V -0.3V to +0.3V -0.3V to 6V -0.
PAGE 3
DS2715: NiMH Battery Pack Charge Controller PARAMETER Current Sense Comparator Gain SYMBOL GCOMP CONDITIONS (Note 7) MIN TYP MAX UNITS Ω-1 10 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 Battery Pack Charge Controller PARAMETER SYMBOL dT/dt Blanking Time tBLANK PRECHARGE Timeout tPC-TO FAST-CHARGE Timer Range tFC TOPOFF to FASTCHARGE Duration Ratio Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: CONDITIONS MIN TYP MAX UNITS 3.85 4.3 4.75 Min 30 0.5 Min 6 DS2715 1:2 DS2715B 1:4 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.
PAGE 5
DS2715: NiMH Battery Pack Charge Controller Figure 1.
PAGE 6
DS2715: NiMH Battery Pack Charge Controller Di sc h ar g eL atc h Di sc ha se t rg e la tc h se t Figure 2.
PAGE 7
DS2715: NiMH Battery 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 while the cell pack is already inserted, or with the detection of cell insertion after power-up.
PAGE 8
DS2715: NiMH Battery Pack Charge Controller PRESENCE The DS2715 enters the PRESENCE state whenever VDD > VUVLO and VBATT > VOPEN indicating that the charge source is present, but no cell is available to charge. The DS2715 will remain in the PRESENCE state until a cell is inserted into the circuit causing the voltage on VBATT to fall below 1.
PAGE 9
DS2715: NiMH Battery Pack Charge Controller Suspension of charge activity is possible by floating the RT pin. The state machine and all timers are reset to their presence test conditions when suspending from a charge mode. The DISCHARGE mode is not affected by the SUSPEND function. The Vch output is high-impedance for charging modes, and operates as normal for DISCHARGE mode during SUSPEND.
PAGE 10
DS2715: NiMH Battery Pack Charge Controller as a discharge path to the load. Hysteresis on the comparator input provides the difference between the ON and OFF state thresholds. In a closed-loop regulation circuit, the comparator regulates voltage across the sense resistor as referenced to the SNS pins to a DC average of: VSNS = VFC + 0.5 x VHYS-FC = -0.107V during FAST-CHARGE VSNS = VTO + 0.5 x VHYS-TO = -0.
PAGE 11
DS2715: NiMH Battery Pack Charge Controller Figure 3. Ideal Comparator Input and Charge Control Output Waveforms Not drawn to scale VPullup VCH VOL |VFC| |Vsns| |Vsns(DC)| |VFC + VHYS-FC| Time Charge Rate Selection The charge rate is determined by an external sense resistor connected between the SNS+ and SNS- pins. The DS2715 will regulate the charge current to maintain a voltage drop of VFC (or VFC + 0.5 x VHYS-FC in comparator mode) across the sense resistor during FAST-CHARGE.
PAGE 12
DS2715: NiMH Battery 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 10k NTC thermistor between THM and VSS, and a 10k 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 13
DS2715: NiMH Battery Pack Charge Controller Application Circuits Switchmode Figure 5 shows a typical DS2715 switchmode application circuit for charging a 3-cell battery stack. Connecting the MODE pin to CBIAS enables the comparator mode of current regulation. The DS2715 regulates the current through the current sense resistor R7 by switching Q1 on and off as the sense resistor voltage ramps up and down toward the preset sense voltage thresholds. The .
PAGE 14
DS2715: NiMH Battery Pack Charge Controller The RT resistor (R5) is set to 47kΩ for a timeout of 70 minutes. This would be appropriate for cells with a capacity of about 1Ah when charged with the 1.07A charge current. The resistor divider with R12 and R13 is configured to present the voltage equivalent to a single cell on the Vbatt pin. The value of L1 in the example represents a moderate switching speed of 100-150khz for fast-charge mode.
PAGE 15
DS2715: NiMH Battery Pack Charge Controller Cell Stack Size Adjustment R12 and R13 of the application circuits form a voltage divider such that the voltage of a single cell is present on the Vbatt pin. This is required for proper operation of the DS2715. Given a 100kΩ resistor for R13, adjust R12 as follows for the number of cells in the battery pack: R12 = (Number of Cells -1) * R13 To charge 3-cell stacks, a value of 200kΩ is used for R12 for a 100kΩ R13.
PAGE 16
DS2715: NiMH Battery Pack Charge Controller Figure 7. Switching Circuit with Example Layout Control R1 D2 + - Charge Source Side Q1 Loop1 C1 L1 D1 C2 Loop2 C3 +Battery Side - Loop Areas Minimized Charge Source Side + C 1 D1 C2 R 1 C3 - Battery + Side L1 Q1 D2 Backside Ground Plane Control Another important layout detail is the connection of the sense resistor.
PAGE 17
DS2715: NiMH Battery Pack Charge Controller REVISION HISTORY REVISION DATE 011408 DESCRIPTION Various comprehensive changes. 031609 Added device version DS2715B 042809 Updated Ordering Information table. PAGES CHANGED 1, 3, 4, 6–15 1,4,7,8,10 1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.