Rainbow Electronics DS2770 User Manual

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DS2770

Battery Monitor and Charge Controlle

FEATURES

§ Integrated charge controller supporting both

rechargeable lithium and NiMH battery technologies

§ Available in two configurations:

– Internal 25mW current-sense resistor – External user-selectable sense resistor

§ Current measurement:

– 15-bit bidirectional measurement – Internal sense resistor configuration:

62.5mA LSB and ±2A dynamic range

– External sense resistor configuration:

1.56mV LSB and ±51.2mV dynamic range

§ Current accumulation

– Internal sense resistor: 0.25mAh LSB – External sense resistor: 6.25mVh LSB

§ Voltage measurement with 4.88mV resolution

§ Temperature measurement using integrated

sensor with 0.125°C resolution

§ 40 bytes of lockable EEPROM

§ 16 bytes of general-purpose SRAM

§ 42-day timer

§ Dallas 1-Wire

§ 1.8V logic levels

§ Low power consumption:

– Active current: 80mA typical – Sleep current: 0.5mA typical

interface with 64-bit ID

PIN ASSIGNMENT

UV VDD

VCH

SNS

IS2

DS2770

16-Pin TSSOP

VIN

VSS

IS1

PIN DESCRIPTION

UV – Battery Undervoltage Detect Output CC – Charge Control Output VCH – Charge Supply Input SNS – Sense Resistor Connection IS2 – Current-Sense Input IS1 – Current-Sense Input VSS – Device Ground DQ – Data Input/Output VIN – Voltage Sense Input VDD – Power Supply Input NC – No Connect

ORDERING INFORMATION

ORDERING NUMBER MARKING DESCRIPTION

DS2770AE D2770EA TSSOP, Ext. Sense Res., 4.1V Charge Voltage DS2770BE D2770EB TSSOP, Ext. Sense Res., 4.2V Charge Voltage DS2770AE/T&R D2770EA DS2770AE on Tape & Reel DS2770BE/T&R D2770EB DS2770BE on Tape & Reel DS2770AE-025 2770EAR TSSOP, 25mW Sense Res., 4.1V Charge Voltage DS2770BE-025 2770EBR TSSOP, 25mW Sense Res., 4.2V Charge Voltage DS2770AE-025/T&R 2770EAR DS2770AE-025 on Tape & Reel DS2770BE-025/T&R 2770EBR DS2770BE-025 on Tape & Reel

1-Wire is a registered trademark of Dallas Semiconductor.

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DS2770

DESCRIPTION

The DS2770 battery monitor and charge controller performs several functions needed for thorough battery maintenance. When used in conjunction with the host system’s processor, a battery-pack resident DS2770 may be utilized for applications that include charging, remaining capacity estimation, safety monitoring, and nonvolatile (NV) parametric storage.

The DS2770 provides a unique ID, a digital temperature sensor, an analog-to-digital converter (ADC) that measures battery voltage and current, an integrated current accumulator that keeps a running total of all current entering and leaving the battery, an elapsed time meter, NV memory for storage of important parameters, and an integrated charge controller supporting rechargeable lithium (including lithium-ion and lithium-ion polymer) and nickel metal hydride (NiMH) batteries. Current measurement can be accomplished through the use of an integrated 25mW sense resistor or through an external sense resistor. The resolution of the current, voltage, and temperature measurements is sufficient for process monitoring applications such as battery-charge control and safety. The charge-control technique is user-selectable to support either pulse charge for rechargeable lithium or dT/dt termination for NiMH. Additionally, programmable charge timers and low-battery recovery are provided for safety and convenience.

Information is sent to/from the DS2770 over a 1-Wire interface so that only one wire (and ground) needs to be connected from a processor to a DS2770. This means that DS2770-equipped battery packs need only four output connectors: battery power, charge source, ground, and the 1-Wire interface. Each device has a factory-programmed 64-bit net address that allows it to be individually addressed by the host system.

Two types of memory are provided on the DS2770 for battery information storage: lockable EEPROM and SRAM. EEPROM memory saves important battery data in true NV memory that is unaffected by severe battery depletion, accidental shorts, or ESD events and becomes ROM when locked to provide additional security for unchanging battery data. SRAM provides inexpensive storage for temporary data.

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BLOCK DIAGRAM Figure 1

1-WIRE

INTERFACE

AND

ADDRESS

DS2770

REGISTERS AND

USER MEMORY

VIN

IS1

IS2

VCH

SNS

THERMAL

SENSE

VOLTAGE

REFERENCE

MUX

Internal sense resistor configuration only

25m

ADC

LOCKABLE EEPROM

SRAM

TEMPERATURE

VOLTAGE

CURRENT

ACCUM CURRENT

TIMEBASE

TIMER

STATUS/CONTROL

CHARGE CONTROL

CHIP GROUND

VSS

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DETAILED PIN DESCRIPTION Table 1

PIN SYMBOL DESCRIPTION

DS2770

Battery Undervoltage Detect Output: This pin allows charge of the

battery at a reduced rate when the battery cell voltage is less than the low battery voltage threshold, V

Charge Control Output: Charge of the battery is controlled through this

pin when battery cell voltage is greater than or equal to V

3VCH

Charge Supply Input: The charge source is connected to this pin and is

measured by the DS2770 to determine if a charge source is present.

4, 5, 6 SNS Sense Resistor Connection: Connect to the negative terminal of the

battery pack. In the internal sense resistor configuration, the sense resistor is connected between VSS and SNS.

8IS2

Current-Sense Input: This pin is internally connected to SNS through a

W resistor. Connect a 0.1mF capacitor between IS2 and IS1 to

10k complete a lowpass filter.

9IS1Current-Sense Input: This pin is internally connected to VSS through a

W resistor. Connect a 0.1mF capacitor between IS1 and IS2 to

10k complete a lowpass filter.

11, 12, 13 VSS

Device Ground: Connect directly to the negative terminal of the battery

cell. For the external sense resistor configuration, connect the sense resistor between VSS and SNS.

14 DQ Data Input/Out: 1-Wire data line. Open-drain output driver. Connect this

pin to the DATA terminal of the battery pack. Pin has an internal pulldown for sensing disconnection.

15 VIN

Voltage Sense Input: The voltage on the battery cell is monitored via this

input pin.

16 VDD Power Supply Input: Input supply voltage for the DS2770 (2.7V to

5.5V)

7, 10 NC

Do not connect.

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APPLICATION EXAMPLE Figure 2

PACK+

DS2770

CHARGE SOURCE

4403

FMMT718

360W

4.7kW 1kW1kW100W150W

CC VCH

0.1mF0.1mF

SNS

NC IS2

VDD

VIN

VSS

IS1

0.1mF

5.1V

Lithium

Protection

Circuit

PACK-

DATA

1 — R 2 — R

(1)

SNS

150W

DS2770

SNS-INT

IS2 IS1

is present for external sense resistor configuration only.

SNS

is present for internal sense resistor configuration only.

SNS-INT

10KW

Voltage

Sense

(2)

VSSSNS

10KW

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DS2770

POWER MODES

The DS2770 has two possible power modes: Active Mode and Sleep Mode. While in Active Mode, the DS2770 continually measures current, voltage, temperature, and time. Also, current flow is accumulated, charge control is provided, and data is available to the host system. In Sleep Mode, the DS2770 ceases these activities. The DS2770 can enter Sleep Mode only when the PMOD bit in the Status Register is set to 1 and the following other conditions occur:

§ The CINI bit is set to 0 and the DQ line is held low for longer than two seconds. If a charge is in

progress, charging will immediately stop and the device will begin transition to Sleep Mode.

§ The CINI bit is set to 1 and the DQ line is held low for longer than two seconds. If a charge is in

progress, the DS2770 will not go into Sleep Mode until the charge operation is completed.

The DS2770 returns to Active Mode when any of the following occurs:

§ The DQ line is pulled high.

§ The voltage on VCH becomes greater than VDD (charger connection) with the CINI bit set to 1.

Once the DS2770 identifies the 2 second DQ low condition, a transition to Sleep Mode begins. This process will take up to an additional 11 seconds before the supply current drops to I The DS2770 defaults to Active Mode when power is first applied to VDD.

SLEEP

levels.

CHARGER FUNCTION

The DS2770 operates as a standalone charge controller supporting rechargeable lithium and NiMH battery technologies. The battery type to be charged is selectable through the CTYPE bit of the Status Register (0 for rechargeable lithium and 1 for NiMH). Charge control of both battery types is performed by on/off gating of an external constant current or current-limited charge source. If the battery voltage is

less than V

battery at a reduced rate before fast charging can begin. In Figure 2’s application circuit, trickle-charge current limited by a 360

characteristics of the charge source.

including pack temperature and the status of the CINI bit. reaches V respectively, in the CSTAT1 and CSTAT0 bits of the Status Register assuming any previous charge sequence completed status has been cleared.

Fast charging can be initiated by one of two methods:

1) Issuing a Start Charge command [B5h].

2) Introducing a charge supply on the VCH pin when the CINI bit in the Status Register is a 1.

Note that if VDD is below approximately 1.8V prior to using either initiation method, fast charge will not start after the battery is trickle charged to V

and a charge source is present, pin UV is driven low, signifying the need to recover the

UV gates a

W series resistor. Selection of this resistor depends on the

UV is driven low independent of any other state of the pack,

UV is driven high when the battery voltage

. While trickle charging, a “charge in progress” status is indicated with (0, 1) values,

After initiation, the start of fast charge may be postponed if any of the following conditions exist:

§ The temperature is outside the valid charge window specified by T

(0°C) and TCH (40°C).

§ Charge source is not present (VCH < VDD).

§ Conversion data is not valid (data becomes valid 110ms after waking from Sleep Mode).

§ Battery voltage is less than the low-battery-voltage threshold, V

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, (3.0V).

DS2770

After initiation and clearing of the above conditions, fast charging begins with the CC pin driven low.

During fast charging,

which

CC is driven high for approximately 27ms every 55ms. As long as the charge source remains

CC remains low, except for periodic testing of premature charge source removal in

connected and the temperature remains in the valid range, charging will proceed per the method selected

by the CTYPE bit. If the charge source is removed or the Stop Charge command [BEh] is issued,

CC is driven high and charging must be reinitiated by one of the two charge initiation methods described previously. Charging will also be stopped if the DQ line is low for >2s and the CINI bit is set to 0. Assuming any previous charge status has been cleared, a “charge in progress” status is indicated during fast charging with (0, 1) values, respectively, in the CSTAT1 and CSTAT0 bits of the Status Register.

Upon charge completion according to the method selected with the CTYPE bit, or completion due to

either of the secondary methods, pin

CC will return to the high state, and a charge done condition will be flagged with (1, 1) values in the CSTAT1 and CSTAT0 bits of the Status Register. Note that the charge done status is latched and must be cleared by a write of any value to the Status Register. Once charging has been completed or aborted, the DS2770 may either enter the Sleep Mode or remain active, depending on the state of the PMOD bit described previously in the Power Modes section.

RECHARGEABLE LITHIUM CHARGER OPERATION

Fast charging of lithium cell types is performed in two distinct regions. The bulk charge region delivers most of the charge to the cell by gating current from the charge source while the battery voltage is below

the charge voltage threshold, V switch. When the battery voltage reaches V

is employed that allows

CC to remain low for a delay period of t

high. When the battery voltage decays below V

pulse region of charge continues with the

. The CC pin remains low, driving a PNP or P-channel MOSFET

, the pulse region begins in which a pulse-charge technique

(875ms) after which CC is driven

VCV

, CC is again driven low and the cycle is repeated. The

CC duty cycle slowly changing. Eventually, the battery voltage

decay time, and thus the

charge decay time limit, t

CC high time, becomes longer than 13.125s, and charge is terminated. The

, includes one 875ms period of CC low and 15 periods high for a total time of

14s. The average charge rate at termination is 1/16 of the rate set by the charge source. See Figure 3 for an illustration of the t

decay method. See the Secondary Charge Termination section for the secondary

termination means based on time or temperature included for increased safety.

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RECHARGEABLE LITHIUM PULSE CHARGING Figure 3

VIN

DS2770

VCV

Trickle

Charge

Bulk

Region

Pulse

Region

Pulse Charge

Charge

Complete

NiMH CHARGER OPERATION

During NiMH charging, charge current from a constant current or current-limited supply is gated to the

battery under control of when the battery reaches 3.0V, a three-cell NiMH battery will begin fast charge at 1.0V per cell. A voltage divider can be used to adjust the transition point to a higher per cell voltage, though values in the Voltage Measurement Register would be affected by the divider ratio.

At the start of fast charge, the DS2770 uses the most recent temperature measurement to determine the appropriate dT/dt termination rate for the ambient conditions from Table 2 below. During the first 5 minutes, temperature rate termination is blanked to avoid false dT/dt detection due to I the blanking period, dT/dt detection begins using one of the initial rates from Table 2 and requires that the rate of temperature rise continue at or above the selected rate for 2.8 minutes. Internally, values from the Temperature Measurement Register are averaged in determining the sustained rate of temperature rise. The effective rate shown in Table 2 is based on NiMH charge data and represents the predicted instantaneous dT/dt rate at termination.

UV and CC pins. Since the transition from trickle charge to fast charge occurs

R heating. After

NiMH CHARGE TERMINATION THRESHOLDS Table 2

dT/dt THRESHOLDAMBIENT

TEMPERATURE (°C)

0 to +5 0.30 1.0

+5 to +15 0.45 1.0

+15 to +40 0.60 1.0

INITIAL

(°C/MIN)

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EFFECTIVE

(°C/MIN)

DS2770

SECONDARY CHARGE TERMINATION

Two secondary charge terminations are included. Independent of battery technology selection, charge terminates if the maximum charge temperature is exceeded or the charge timer expires. The CSTAT1 and CSTAT0 bits in the Status Register will both be set to 1 to indicate a “charge sequence completed” status.

The maximum temperature threshold, T

during charge, the charge is terminated.

MCT

, is fixed at +50°C. If the temperature measurement exceeds

MCT

The maximum charge time is set in the Charge Time Register, CTR. CTR is initialized from lockable

EEPROM location address 34h at the start of fast charge ( decrements by one count every 56 seconds (t

) during fast charge. If CTR reaches zero, charging is

CTR

CC driven low after initiation). CTR

terminated. Since CTR is writable, the value in CTR may be overwritten at any time during a charge to modify the maximum charge time. Figure 4 shows the format of CTR.

CHARGE TIME REGISTER Figure 4

Address 06

272625242322212

MSb LSb

Units: 0.015625h

CURRENT MEASUREMENT

In the Active Mode of operation, the DS2770 continually measures the current flow into and out of the battery by measuring the voltage drop across a current-sense resistor. The DS2770 is available in two configurations: 1) internal 25m either configuration, the DS2770 considers the voltage difference between pins IS1 and IS2 (V

) to be the filtered voltage drop across the sense resistor. A positive VIS value indicates current is

IS2

flowing into the battery (charging), while a negative V battery (discharging). Note that when an external sense resistor is used, one end of the resistor must be wired directly to VSS (the negative terminal of the cell) for proper operation of the current measurement circuitry.

W current-sense resistor; 2) external user-selectable sense resistor. In

= V

IS1

value indicates current is flowing out of the

is measured with a signed resolution of 15 bits. Measurements are updated in the Current Register in

two’s complement format every 3.52 seconds. The Current Register value represents the average current over 3.52 seconds. Currents outside the register’s range are reported at the limit of the range. Figure 5 shows the format of the Current Register.

For the internal sense resistor configuration, the DS2770 maintains the Current Register in units of amps, with a resolution of 62.5

mA and a full-scale range of ±2.048A. The DS2770 automatically compensates

for internal sense resistor process variations and temperature effects when reporting current.

For the external sense resistor configuration, the DS2770 writes the measured V Register, with a resolution of 1.56

mV and a full-scale range of ±51.2mV.

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voltage to the Current

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