MAXIM DS2760 User Manual
www.maxim-ic.com
DS2760
High-Precision Li+ Battery Monitor
FEATURES
§ Li+ safety circuit
- Overvoltage protection
- Overcurrent/short circuit protection
- Undervoltage protection
§ Zero Volt Battery Recovery Charge
§ Available in two configurations:
- Internal 25mW sense resistor
- External user-selectable sense resistor
§ Current measurement
- 12-bit bidirectional measurement
- Internal sense resistor configuration:
0.625mA LSB and ±1.9A dynamic range
- External sense resistor configuration:
15.625mV LSB and ±64mV dynamic range
§ Current accumulation
- Internal sense resistor: 0.25mAhr LSB
- External sense resistor: 6.25mVhr LSB
§ Voltage measurement with 4.88mV resolution
§ Temperature measurement using integrated
sensor with 0.125°C resolution
§ System power management and control feature
support
§ 32 bytes of lockable EEPROM
§ 16 bytes of general purpose SRAM
§ Dallas 1-Wire® interface with unique 64-bit
device address
§ Low power consumption:
- Active current: 90mA max
- Sleep current: 2mA max
PIN ASSIGNMENT
CC VIN
1
SNS
SNS
SNS
1
2
PLS
2
3
2
DC
4
5
6
7
DQ
8
IS2
DS2760
16-Pin TSSOP Package
16
15
14
13
12
11
10
9
V
DD
PIO
VSS
VSS
VSS
PS
IS1
1 2 3 4
SNS
PLS DC DQ
SNS
CC IS2
Probe
VSS
VIN IS1
Probe
VDD PIO PS
VSS
DS2760
Flip-Chip Packaging
Top View
PIN DESCRIPTION
- Charge control output
CC
- Discharge control output
DC
DQ - Data input/output
PIO - Programmable I/O pin
PLS - Battery pack positive terminal input
- Power switch sense input
PS
VIN - Voltage sense input
VDD - Power supply input (2.5V to 5.5V)
VSS - Device ground
SNS - Sense resistor connection
IS1 - Current sense input
IS2 - Current sense input
SNS Probe - Do not connect
VSS Probe - Do not connect
A
B
C
D
E
F
1-Wire is a registered trademark of Dallas Semiconductor.
1 of 25 010906
DS2760
ORDERING INFORMATION
Part Marking Description
DS2760AE+ DS2760A TSSOP, External Sense Resistor, 4.275V Vov, Lead-Free
DS2760BE+ DS2760B TSSOP, External Sense Resistor, 4.35V Vov, Lead-Free
DS2760AE+T&R DS2760A DS2760AE+ on Tape & Reel, Lead-Free
DS2760 BE+T&R DS2760B DS2760BE+ on Tape & Reel, Lead-Free
DS2760AE+025 2760A25
DS2760BE+025 2760B25
DS2760AE+025/T&R 2760A25 DS2760AE+025 in Tape & Reel, Lead-Free
DS2760BE+025/T&R 2760B25 DS2760BE+025 in Tape & Reel, Lead-Free
DS2760AX DS2760A Flipchip, External Sense Resistor, Tape & Reel, 4.275V Vov
DS2760BX DS2760B Flipchip, External Sense Resistor, Tape & Reel, 4.35V Vov
DS2760AX-025 DS2760AR
DS2760BX-025 DS2760BR
DS2760AE DS2760A TSSOP, External Sense Resistor, 4.275V Vov
DS2760BE DS2760B TSSOP, External Sense Resistor, 4.35V Vov
DS2760AE/T&R DS2760A DS2760AE on Tape & Reel
DS2760 BE/T&R DS2760B DS2760BE on Tape & Reel
DS2760AE-025 2760A25
DS2760BE-025 2760B25
DS2760AE-025/T&R 2760A25 DS2760AE-025 in Tape & Reel
DS2760BE-025/T&R 2760B25 DS2760BE-025 in Tape & Reel
TSSOP, 25mW Sense Resistor, 4.275V Vov, Lead-Free
TSSOP, 25mW Sense Resistor, 4.35V Vov, Lead-Free
Flipchip, 25mW Sense Resistor, Tape & Reel, 4.275V Vov
Flipchip, 25mW Sense Resistor, Tape & Reel, 4.35V Vov
TSSOP, 25mW Sense Resistor, 4.275V Vov
TSSOP, 25mW Sense Resistor, 4.35V Vov
DESCRIPTION
The DS2760 High-Precision Li+ Battery Monitor is a data acquisition, information storage, and safety
protection device tailored for cost-sensitive battery pack applications. This low-power device integrates
precise temperature, voltage, and current measurement, nonvolatile data storage, and Li+ protection into
the small footprint of either a TSSOP package or flip chip. The DS2760 is a key component in
applications including remaining capacity estimation, safety monitoring, and battery-specific data storage.
Via its 1-Wire interface, the DS2760 gives the host system read/write access to status and control
registers, instrumentation registers, and general purpose data storage. Each device has a unique factoryprogrammed 64-bit net address which allows it to be individually addressed by the host system,
supporting multi-battery operation.
The DS2760 is capable of performing temperature, voltage and current measurement to a resolution
sufficient to support process monitoring applications such as battery charge control, remaining capacity
estimation, and safety monitoring. Temperature is measured using an on-chip sensor, eliminating the need
for a separate thermistor. Bidirectional current measurement and accumulation are accomplished using
either an internal 25mW sense resistor or an external device. The DS2760 also features a programmable
I/O pin that allows the host system to sense and control other electronics in the pack, including switches,
vibration motors, speakers and LEDs.
Three types of memory are provided on the DS2760 for battery information storage: EEPROM, lockable
EEPROM and SRAM. EEPROM memory saves important battery data in true nonvolatile memory that
is unaffected by severe battery depletion, accidental shorts or ESD events. Lockable EEPROM becomes
ROM when locked to provide additional security for unchanging battery data. SRAM provides
inexpensive storage for temporary data.
2
BLOCK DIAGRAM Figure 1
DQ
THERMAL
SENSE
VIN
IS1
+
IS2
PLS
PS
SNS
1-WIRE
INTERFACE
AND
ADDRESS
MUX
-
internal sense resistor configuration only
IS2 IS1
REFERENCE
25mW
VOLTAGE
ADC
REGISTERS AND
USER MEMORY
LOCKABLE EEPROM
SRAM
TEMPERATURE
VOLTAGE
CURRENT
ACCUM. CURRENT
STATUS / CONTROL
LI+ PROTECTION
chip ground
DS2760
TIMEBASE
PIO
CC
DC
VSS
3
DETAILED PIN DESCRIPTION Table 1
SYMBOL TSSOP* FLIP
CHIP*
DS2760
DESCRIPTION
CC
1 C1 Charge Protection Control Output. Controls an external p-channel
high-side charge protection FET.
DC
3 B2 Discharge Protection Control Output. Controls an external p-channel
high-side discharge protection FET.
DQ 7 B4 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
1mA pull-down for sensing disconnection.
PIO
14 E2 Programmable I/O Pin. Used to control and monitor user-defined
external circuitry. Open drain to VSS.
PLS 2 B1 Battery Pack Positive Terminal Input. The device monitors the state of
the battery pack’s positive terminal through this pin in order to detect
events such as the attachment of a charger or the removal of a short
circuit. Additionally, a charge path to recover a deeply depleted cell is
provided from PLS to VDD.
PS
10 E4 Power Switch Sense Input. The device wakes up from Sleep Mode
when it senses the closure of a switch to VSS on this pin. Pin has an
internal 1mA pull-up to VDD.
VIN 16 D1 Voltage Sense Input. The voltage of the Li+ cell is monitored via this
input pin. This pin has a weak pullup to VDD.
VDD 15 E1 Power Supply Input. Connect to the positive terminal of the Li+ cell
through a decoupling network.
VSS
11,12,13 F3 Device Ground. Connect directly to the negative terminal of the Li+ cell.
For the external sense resistor configuration, connect the sense resistor
between VSS and SNS.
SNS 4,5,6 A3 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.
IS1 9 D4 Current Sense Input. This pin is internally connected to VSS through a
4.7kW resistor. Connect a 0.1mF capacitor between IS1 and IS2 to
complete a low-pass input filter.
IS2 8 C4 Current Sense Input. This pin is internally connected to SNS through a
4.7kW resistor.
SNS
N/A C2
Do Not Connect.
Probe
VSS
N/A D2
Do Not Connect.
Probe
* Mechanical drawing for the 16-pin TSSOP and DS2760 flip-chip package can be found at:
http://pdfserv.maxim-ic.com/arpdf/Packages/16tssop.pdf
http://pdfserv.maxim-ic.com/arpdf/Packages/chips/2760x.pdf
4
APPLICATION EXAMPLE Figure 2
(2)
A
0
(1)
102
PACK+
1k
W
1k
150W
1
150W
2
DAT
PACK-
1 – R
2 – R
is present for external sense resistor configurations only
SENS
SENSINT
is present for internal sense resistor configurations only
W
DS2760
CC
PLS
DC
SNS
SNS
SNS
DQ
IS2
VIN
V
DD
PIO
VSS
VSS
VSS
PS
IS1
104
R
W
KS
150
104
4.7kW
4.7kW
DS2760
R
SENSINT
voltage
sense
W
1k
SENS
SNS
R
IS2 IS1
DS2760
BAT+
PS
BAT-
VSS
R
KS
4.7kW
5
DS2760
POWER MODES
The DS2760 has two power modes: Active and Sleep. While in Active Mode, the DS2760 continually
measures current, voltage and temperature to provide data to the host system and to support current
accumulation and Li+ safety monitoring. In Sleep Mode, the DS2760 ceases these activities. The
DS2760 enters Sleep Mode when any of the following conditions occurs:
§ the PMOD bit in the Status Register has been set to 1 and the DQ line is low for longer than
2 seconds (pack disconnection)
§ the voltage on VIN drops below undervoltage threshold VUV for t
(cell depletion)
UVD
§ the pack is disabled through the issuance of a SWAP command (SWEN bit =1)
The DS2760 returns to Active Mode when any of the following occurs:
§ the PMOD bit has been set to 1 and the SWEN bit is set to 0 and the DQ line is pulled high
(pack connection)
§ the PS pin is pulled low (power switch)
§ the voltage on PLS becomes greater than the voltage on VIN (charger connection) with the SWEN bit
set to 0
§ the pack is enabled through the issuance of a SWAP command (SWEN bit =1)
The DS2760 defaults to Sleep Mode when power is first applied.
LI+ PROTECTION CIRCUITRY
During Active Mode, the DS2760 constantly monitors cell voltage and current to protect the battery from
overcharge (overvoltage), overdischarge (undervoltage) and excessive charge and discharge currents
(overcurrent, short circuit). Conditions and DS2760 responses are described in the sections below and
summarized in Table 2 and Figure 3.
LI+ PROTECTION CONDITIONS AND DS2760 RESPONSES Table 2
Activation Condition
Name
Overvoltage VIN > V
Undervoltage VIN < V
Threshold Delay Response
OV
UV
t
OVD CC
t
UVD CC
high
, DC high,
Sleep Mode
Overcurrent, Charge V
Overcurrent, Discharge V
Short Circuit V
VIS = V
IS1
– V
. Logic high = V
IS2
IS
IS
SNS
< -V
PLS
(2)
> V
> V
OC
OC
(2)
SC
t
OCD CC
t
OCD DC
t
SCD DC
for CC and VDD for
, DC high
high
high
All voltages are with respect to VSS. I
DC
.
references current delivered from pin SNS.
(1) If V
charges the battery and allows V
<2.2V, release is delayed until the recovery charge current (IRC) passed from PLS to VDD
DD
to exceed 2.2V.
DD
(2) for the internal sense resistor configuration, the overcurrent thresholds are expressed in terms of
current: I
(3) with test current I
(4) with test current I
> IOC for charge direction and I
SNS
current flowing from PLS to VSS (pull-down on PLS)
TST
current flowing from VDD to PLS (pull-up on PLS)
TST
< -IOC for discharge direction
SNS
Overvoltage. If the voltage of the cell exceeds overvoltage threshold V
overvoltage delay t
, the DS2760 shuts off the external charge FET and sets the OV flag in the
OVD
Protection Register. When the cell voltage falls below charge enable threshold V
for a period longer than
OV
CE
Release
Threshold
VIN < V
V
PLS
> V
DD
CE
(1)
(charger connected)
V
PLS
V
> VDD – V
PLS
> VDD – V
V
PLS
< VDD – V
TP
TP
TP
(3)
(4)
(4)
SNS
, the DS2760 turns the
6
DS2760
charge FET back on (unless another protection condition prevents it). Discharging remains enabled
during overvoltage.
Undervoltage. If the voltage of the cell drops below undervoltage threshold VUV for a period longer than
undervoltage delay t
Protection Register, and enters Sleep Mode. The DS2760 provides a current-limited (I
, the DS2760 shuts off the charge and discharge FETs, sets the UV flag in the
UVD
) recovery
RC
charge path from PLS to VDD to gently charge severely depleted cells. The recovery path is enabled
when 0 £ VDD < 3V(typ). Once VDD reaches 3V(typ), the DS2760 will return to normal operation,
awaiting connection of a charger to turn on the charge FET and pull out of Sleep Mode.
Overcurrent, Charge Direction. The voltage difference between the IS1 pin and the IS2 pin (V
– V
) is the filtered voltage drop across the current sense resistor. If VIS exceeds overcurrent threshold
IS2
for a period longer than overcurrent delay t
V
OC
, the DS2760 shuts off both external FETs and sets the
OCD
IS
= V
IS1
COC flag in the Protection Register. The charge current path is not re-established until the voltage on the
PLS pin drops below V
– VTP. The DS2760 provides a test current of value I
DD
from PLS to VSS to
TST
pull PLS down in order to detect the removal of the offending charge current source.
Overcurrent, Discharge Direction. If VIS is less than –VOC for a period longer than t
, the DS2760
OCD
shuts off the external discharge FET and sets the DOC flag in the Protection Register. The discharge
current path is not re-established until the voltage on PLS rises above VDD – VTP. The DS2760 provides a
test current of value I
from VDD to PLS to pull PLS up in order to detect the removal of the offending
TST
low-impedance load.
Short Circuit. If the voltage on the SNS pin with respect to VSS exceeds short circuit threshold VSC for
a period longer than short circuit delay t
, the DS2760 shuts off the external discharge FET and sets the
SCD
DOC flag in the Protection Register. The discharge current path is not re-established until the voltage on
PLS rises above VDD – VTP. The DS2760 provides a test current of value I
from VDD to PLS to pull
TST
PLS up in order to detect the removal of the short circuit.
LITHIUM-ION PROTECTION CIRCUITRY EXAMPLE WAVEFORMS Figure 3
V
7
CELL
charge
V
IS
discharge
(1)
CC
DC
t
OVD
t
OVD
t
t
t
OCD
t
Sleep
Mode
(1) To allow the device to react quickly to short circuits, detection is actually done on the SNS pin rather
than on the filtered IS1 and IS2 pins. The actual short circuit detect condition is V
> VSC.
SNS
V
OV
V
CE
V
UV
V
OC
0
-V
OC
-V
SC
V
PLS
VSS
VDD
VSS
active
inactive
DS2760
Summary. All of the protection conditions described above are OR’ed together to affect the CC and DC
outputs.
= (Undervoltage) or (Overcurrent, EITHER Direction) or (Short Circuit) or
DC
(Protection Register bit DE = 0) or (Sleep Mode)
= (Overvoltage) or (Undervoltage) or (Overcurrent, Charge Direction) or (Protection Register
CC
bit CE = 0) or (Sleep Mode)
CURRENT MEASUREMENT
In the Active Mode of operation, the DS2760 continually measures the current flow into and out of the
battery by measuring the voltage drop across a current sense resistor. The DS2760 is available in two
configurations: (1) internal 25mW current sense resistor, and (2) external user-selectable sense resistor. In
either configuration, the DS2760 considers the voltage difference between pins IS1 and IS2 (VIS = V
V
) to be the filtered voltage drop across the sense resistor. A positive VIS value indicates current is
IS2
IS1
–
flowing into the battery (charging), while a negative VIS value indicates current is flowing out of the
battery (discharging).
VIS is measured with a signed resolution of 12-bits. The current register is updated in two’s complement
format every 88ms (128/fsample) with an average of 128 readings. Currents outside the range of the
register are reported at the limit of the range. The format of the Current Register is shown in Figure 4.
For the internal sense resistor configuration, the DS2760 maintains the Current Register in units of Amps,
with a resolution of 0.625mA and full scale range of no less than ±1.9A (see Note 7 on IFS spec for more
details). The DS2760 automatically compensates for internal sense resistor process variations and
temperature effects when reporting current.
For the external sense resistor configuration, the DS2760 writes the measured VIS voltage to the Current
Register, with a resolution of 15.625mV and a full scale range of ±64mV.
CURRENT REGISTER FORMAT Figure 4
MSB—Address 0E LSb—Address 0F
11
S 2
210 29 28 27 26 25 24 23 22 21 20 X X X
MSb LSb MSb LSb
Units: 0.625 mA for internal sense resistor
15.625 mV for external sense resistor
CURRENT ACCUMULATOR
The Current Accumulator facilitates remaining capacity estimation by tracking the net current flow into
and out of the battery. Current flow into the battery increments the Current Accumulator while current
flow out of the battery decrements it. Data is maintained in the Current Accumulator in two’scomplement format. The format of the Current Accumulator is shown in Figure 5.
When the internal sense resistor is used, the DS2760 maintains the Current Accumulator in units of Amphours, with a resolution of 0.25mAhrs and full scale range of ±8.2Ahrs. When using an external sense
8
Loading...