Owner's manual

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DESCRIPTION

The DS2711 and DS2712 are ideal for in-system or

stand-alone charging of 1 or 2 AA or AAA NiMH

“loose” cells. Temperature, voltage, and charge time

are monitored to provide proper fast charging control

algorithms for nickel metal hydride (NiMH) batteries.

Battery tests are included to detect defective or

inappropriate cells such as alkaline primary batteries.

The DS2711/DS2712 support series and parallel

topologies, with independent monitoring and control of

each cell. Charging of NiCd chemistry cells is also

supported.

FEATURES

§ Charge 1 or 2 NiMH Cells

§ Detect and Avoid Charging Alkaline Cells

§ Precharge Deeply Depleted Cells

§ Fast Charge NiMH with -DV Termination

Sensitivity of 2mV (typ)

§ Monitor Voltage, Temperature, and Time for

Safety and Secondary Termination

§ Regulate Charge Current:

Linear Control (DS2711)

Switch-Mode Control (DS2712)

§ Drive PMOS or PNP-Type Pass Element or

Switch, or an Optocoupler

§ Compatible with Popular Optocouplers and

Integrated Primary Side PWM Controllers

§ Small 16-Pin SO Package

APPLICATIONS

Desktop/Stand-Alone Chargers (AAA/AA)

Digital Still Cameras

Music Players

Games

Toys

PIN CONFIGURATION

VP2

VP1

CC1

CC2

LED1

VSS

LED2

CSOUT

VN1

VN0

THM2

THM1

VDD

TMR

CTST

DMSEL

PIN DESCRIPTION

PIN NAME FUNCTION

1 CC1 Cell 1 Charge-Control Output

2 CC2 Cell 2 Charge-Control Output

3 LED1 Cell 1 Status

4 V

Ground Reference and Chip-Supply

Return

5 LED2 Cell 2 Status, Mode-Select Input

6 CSOUT Current-Sense Output

7 VN1 Current-Sense + Input

8 VN0 Current-Sense - Input

9 DMSEL Display-Mode Select

10 CTST Cell Test Threshold Set

11 TMR Charge Timer Set

12 V

Chip-Supply Input (4.0V to 5.5V)

13 THM1 Cell 1 Thermistor Input

14 THM2 Cell 2 Thermistor Input

15 VP1 Cell 1 Positive-Terminal Sense Input

16 VP2 Cell 2 Positive-Terminal Sense Input

Table 1. ORDERING INFORMATION

PART MARKING PIN-PACKAGE

DS2711Z

DS2711

16 SOIC

DS2711Z/T&R DS2711

16 SOIC,

Tape-and-Reel

DS2712Z

DS2712

16 SOIC

DS2712Z/T&R DS2712

16 SOIC,

Tape-and-Reel

DS2711/DS2712

Loose Cell NiMH Chargers

www.maxim-ic.com

See Table 1 for Ordering Information.

16 SOIC

Summary of content (13 pages)

PAGE 1
DS2711/DS2712 Loose Cell NiMH Chargers www.maxim-ic.com PIN CONFIGURATION DESCRIPTION The DS2711 and DS2712 are ideal for in-system or stand-alone charging of 1 or 2 AA or AAA NiMH “loose” cells. Temperature, voltage, and charge time are monitored to provide proper fast charging control algorithms for nickel metal hydride (NiMH) batteries. Battery tests are included to detect defective or inappropriate cells such as alkaline primary batteries.
PAGE 2
DS2711/DS2712: Loose Cell NiMH Charger ABSOLUTE MAXIMUM RATINGS* Voltage on All Pins Relative to VSS Voltage on DMSEL Continuous Sink Current CC1, CC2, LED1, LED2 and CSOUT Operating Temperature Range Storage Temperature Range Soldering Temperature -0.3V to +6V VDD + 0.
PAGE 3
PARAMETER Threshold Voltage, Thermistor - Min Threshold Voltage, Thermistor - Max Threshold Voltage, Thermistor - Stop Threshold Current, TMR Pin Suspend Presence Test Current, VP1, VP2 SYMBOL CONDITIONS VTHM-MIN (Notes 1, 4, 6) VTHM-MAX (Notes 1, 4, 6) VTHM-STOP (Notes 1, 4, 6) ITMR-SUS IPTST Parallel: VDD ≥ 4.0V, Series: VDD ≥ 4.5V Reverse Leakage Current, VP1, VP2 ILKGR VDD = 0V, VP1 = 1.5V, VP2 = 3.
PAGE 4
DS2711/DS2712: Loose Cell NiMH Charger Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: Voltages relative to VSS. IMTST current is applied as a source current and as a sink current within 5ms after power-up. When operating in two-cell-series charge configuration, the DMSEL pin must have less than 50pF of external load capacitance for proper operation. If the load capacitance is greater than 50pF, a resistor voltage divider should be used to maintain DMSEL at VDD / 2.
PAGE 5
DS2711/DS2712: Loose Cell NiMH Charger Figure 2. STATE DIAGRAM VDD < VPOR -VHYS (asynchronously from anywhere) POR t < PCTimeout CCx = Hi-Z LEDx = No Battery PreCHG OR VBAT > 1V AND t < PCTimeout AND T < 50C t > PCTimeout OR T > 50 OR VBAT > 1.75V VBAT > 1.75V FAULT Standby power CCx = Hi-Z LEDx = Fault CCx = Hi-Z LEDx = Charging Fast CHG FAIL: VON - VOFF > VCTST VBAT > 1.75V 32 clock interval CCx = Active 48% Par., 97% Ser.
PAGE 6
DS2711/DS2712: Loose Cell NiMH Charger DETAILED DESCRIPTION Charge Algorithm Overview A charge cycle begins in one of three ways: with the application of power to the DS2711 with cell(s) already inserted, with the detection of cell insertion after power-up, or when exiting suspend mode with cell(s) inserted. The charge cycle begins with precharge qualification to prevent fast charging of deeply depleted cells or charging under extreme temperature conditions.
PAGE 7
DS2711/DS2712: Loose Cell NiMH Charger Parallel Charge Configuration The parallel configuration supports two slot stand-alone chargers. Charge pulses are fed alternately to each cell under the control of the CC1 and CC2 pins so the charge regimes occur in parallel. The duty cycle on CC1 and CC2 are independent of one another. Transitions from precharge to fast charge, fast charge to top-off, and top-off to maintenance occur independently for each cell.
PAGE 8
DS2711/DS2712: Loose Cell NiMH Charger DS2712 Parallel Charge Configuration with Switch-Mode Charge Current Regulation The example in Figure 5 uses the DS2712 to regulate charge current as a switching (buck) regulator. ICHG is set to 2A using RSNS = 0.056W. The effective charge current for each cell is ICHG x 0.484 = 968mA. The CSOUT comparator output switches OFF when the voltage across the sense resistor goes above 0.125V and back ON when the voltage drops below 0.100V.
PAGE 9
DS2711/DS2712: Loose Cell NiMH Charger Undervoltage Lockout (UVLO) The UVLO circuit serves as a power-up and brownout detector by monitoring VDD to prevent charging until VDD rises above VUVLO, or when VDD drops below VUVLO - VHYS. If UVLO is active, charging is prevented, the state machine is forced to the RESET state, and all charge timers are reset. A 10ms deglitch circuit provides noise immunity.
PAGE 10
DS2711/DS2712: Loose Cell NiMH Charger Charge Timer The charge timer monitors the duration of charge in fast and top-off charge phases, and is reset at the beginning of each phase. The time-out period is set with an external resistor connected from the TMR pin to VSS. Resistors can be selected to support fast-charge time-out periods of 0.5 to 10 hours and top-off charge time-out periods of 0.25 to 5 hours.
PAGE 11
DS2711/DS2712: Loose Cell NiMH Charger Cell Voltage Monitoring In the 2-cell series mode, the voltage difference between VP2 and VP1 is used to determine the Vcell2 voltage in the two-cell series stack. The voltage difference between VP1 and VN1 is used to determine the Vcell1 voltage. In the 1-cell series mode, the difference between VP1 and VN1 is used as the cell voltage. VP2 can be left floating in the 1-cell series mode.
PAGE 12
DS2711/DS2712: Loose Cell NiMH Charger Table 3. CHARGE MODE SELECTION LED2 PIN STRAPPING MODE Low 1-Cell Series Floating 2-Cell Series High Parallel CC1 and CC2 Outputs The CC1 and CC2 operate as open-drain outputs that drive active low to connect the charge source to the battery cell. During charge, the behavior of the CC1 and CC2 outputs depends on the charge-mode configuration. In parallel mode, CC1 and CC2 are driven low in alternating time slots.
PAGE 13
DS2711/DS2712: Loose Cell NiMH Charger Table 4. PARALLEL CONFIGURATION, EACH CELL MODE CURRENT LIMIT 500mA CURRENT LIMIT 1000mA Cell Capacity Fast 900mAH C/3.72 1700mAH C/7.02 2200mAH C/9.08 900mAH C/1.86 1700mAH C/3.51 2200mAH C/4.54 Precharge/Top-Off Maintenance C/14.4 C/115 C/27.2 C/218 C/35.2 C/282 C/7.20 C/57.6 C/13.6 C/109 C/17.6 C/141 Series and Single Cell Charging Example: In the series and single-cell modes, the effective fast charge current is equal to 0.