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Linear Technology LTC1760 Manual

Dual smart battery system manager
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FEATURES
SMBus Charger/Selector for Two Smart Batteries*
n
Voltage and Current Accuracy within 0.2% of Value
n
Reported by Battery
Simplifies Construction of "Smart Battery System
n
Manager"
Includes All SMBus Charger V1.1 Safety Features
n
Supports Autonomous Operation without a Host
n
Allows Both Batteries to Discharge Simultaneously
n
into Single Load with Low Loss (Ideal Diode)
SMBus Switching for Dual Batteries with Alarm
n
Monitoring for Charging Battery at All Times
Pin Programmable Limits for Maximum Charge
n
Current and Voltage Improve Safety
Fast Autonomous PowerPath
n
Low Loss Simultaneous Charging of Two Batteries
n
>95% Efficient Synchronous Buck Charger
n
AC Adapter Current Limiting* Maximizes Charge Rate
n
SMBus Accelerator Improves SMBus Timing**
n
Available in 48-Lead TSSOP Package
n
APPLICATIONS
Portable Computers and Instruments
n
Standalone Dual Smart Battery Chargers
n
Battery Backup Systems
n
TYPICAL APPLICATION
Dual Battery Charger/Selector System Architecture
DC
IN
SafetySignal 1
SMBus 1
SafetySignal 2
SMBus 2
Switching (<10µs)
™
SYSTEM
POWER
LTC1760
SMBus (HOST)
1760 TA01
For more information
Dual Smart Battery
System Manager
DESCRIPTION
The
LTC
1760
Smart Battery System Manager is a highly-
®
integrated SMBus Level 3 battery charger and selector
intended for products using dual smart batteries. Three
SMBus interfaces allow the LTC1760 to servo to the
internal voltage and currents measured by the batteries
while allowing an SMBus Host device to monitor either
battery's status. Charging accuracy is determined by the
battery's internal voltage and current measurements,
typically better than ±0.2%.
A proprietary PowerPath architecture supports simultane-
ous charging or discharging of both batteries. Typical battery
run times are extended by up to 10%, while charging times
are reduced by up to 50%. The LTC1760 automatically
switches between power sources in less than 10µs to prevent
power interruption upon battery or wall adapter removal.
The LTC1760 implements all elements of a version 1.1
"Smart Battery System Manager" except for the generation
of composite battery information. An internal multiplexer
cleanly switches the SMBus Host to either of the two
attached Smart Batteries without generating partial mes-
sages to batteries or SMBus Host. Thermistors on both
batteries are automatically monitored for temperature and
disconnection information (SafetySignal).
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath is a trademark of Analog Devices, Inc. All other trademarks are the property of their
respective owners. Protected by U.S. Patents including *5723970 **6650174.
Dual vs Sequential Charging
3500
3000
2500
2000
1500
1000
500
0
3500
BAT1
3000
CURRENT
2500
2000
1500
1000
500
0
0
50
BATTERY TYPE: 10.8V Li-Ion (MOLTECH NI2020)
REQUESTED CURRENT = 3A
REQUESTED VOLTAGE = 12.3V
MAX CHARGER CURRENT = 4.1A
www.linear.com/LTC1760
LTC1760
BAT2
BAT1
CURRENT
CURRENT
SEQUENTIAL
BAT2
DUAL
CURRENT
100
MINUTES
100
150
200
250
300
TIME (MINUTES)
1760 TA03
1760fc
1

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Summary of Contents for Linear Technology LTC1760

  • Page 1 (SafetySignal). Standalone Dual Smart Battery Chargers L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Battery Backup Systems PowerPath is a trademark of Analog Devices, Inc. All other trademarks are the property of their respective owners.
  • Page 2 LTC1760 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW DCIN, SCP, SCN, CLP, SCH2 , SW to GND ........–0.3V to 32V PLUS PLUS BAT2 GCH2 SCH1, SCH2 to GND ........–0.3V to 28V GCH1 BAT1 SCH1 BOOST to GND ........... –0.3V to 37V TGATE CSP, CSN, BAT1, BAT2 to GND ....
  • Page 3 LTC1760 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T = 25°C (Note 6). V = 20V, V = 12V, V = 12V, V = 3.3V, DCIN BAT1 BAT2 VDDS = 5.2V unless otherwise noted.
  • Page 4 LTC1760 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T = 25°C (Note 6). V = 20V, V = 12V, V = 12V, V = 3.3V, DCIN BAT1 BAT2 VDDS = 5.2V unless otherwise noted.
  • Page 5 LTC1760 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T = 25°C (Note 6). V = 20V, V = 12V, V = 12V, V = 3.3V, DCIN BAT1 BAT2 VDDS = 5.2V unless otherwise noted.
  • Page 6 PULLUP LTC1760 Driving the Pin SCL1/SDA1/SCL2/SDA2 Pullup Internal to LTC1760 PULLUP Output Low Voltage (V LTC1760 Driving the Pin with Battery SMBus not Connected to Host SMBus SCL1/SDA1/SCL2/SDA2 = 350µA on Host Side PULLUP Output Low Voltage (V LTC1760 Driving the Pin with Battery...
  • Page 7 SENSE compensation components. due to charger offsets. The charging current for requested currents below Note 6: The LTC1760 is tested under pulsed load conditions such that T 4mV/R will be between 4mV/R and (Requested Current – 8mA).
  • Page 8 LTC1760 TYPICAL PERFORMANCE CHARACTERISTICS Dual Battery Charge Time vs Charging Voltage Accuracy Charging Current Accuracy Sequential Battery Charging 3500 BAT2 BAT1 3000 CURRENT CURRENT 2500 –5 2000 SEQUENTIAL 1500 1000 –10 –5 3500 BAT1 –15 3000 CURRENT –10 2500 BAT2...
  • Page 9 GDCO (Pin 6): DCIN Output Switch Gate Drive. Together three PowerPath switch pairs, for detecting short-circuit with GDCI, this pin drives the gate of the P-channel switch current events. Also powers the LTC1760 internal circuitry in series with the DCIN input switch. when all other sources are absent.
  • Page 10 BAT1 (Pin 3), BAT2 (Pin 2): These two pins are the inputs CSN (Pin 34): Current Amplifier CA1 Input. Connect this from the two batteries for power to the LTC1760. to the common output of the charger MUX switches. 1760fc For more information www.linear.com/LTC1760...
  • Page 11 SCL1 (Pin 19): SMBus Clock Signal to Smart Battery 1. Do system power has failed and power is autonomously not connect to an external pull-up. The LTC1760 connects switched to a higher voltage source, if available. this pin to an internal pull-up (I ) when required.
  • Page 12 LTC1760 BLOCK DIAGRAM GB1I GB1O GB2I GB2O GDCI GDCO 100mV SHORT CIRCUIT SWB1 SWB2 SWDC DRIVER DRIVER DRIVER LIMIT LIMIT DECODER LIMIT CHARGE DCIN PUMP 10µA GCH1 SMBALERT SCH1 SEQUENCER MODE GCH2 SCH2 AC_PRESENT BAT1 SMBus BAT2 INTERFACE SCL1 CHARGE...

  • Page 13: Table Of Contents

    2.3.10 AlarmWarning() (0×16) ................................21 2.3.11 AlertResponse() ..................................22 2.4 SMBus Dual Port Operation ................................22 2.5 LTC1760 SMBus Controller Operation ............................... 23 2.6 LTC1760 SMBALERT Operation ................................ 26 3 Charging Algorithm Overview ................................... 26 3.1 Wake-Up Charging Initiation ................................26 3.2 Wake-Up Charging Termination ................................

  • Page 14: Overview

    SMBus Host to be connected to the SMBus of either the two batteries and to prevent current from flowing in battery. The LTC1760 is able to operate as an SMBus a reverse direction in the switch. The amount of current Master or Slave device.
  • Page 15 LTC1760 OPERATION 2.2 Data Bit Definition of Supported SMBus Functions. LTC1760 Data Bit or Nibble Definition/Allowed Values SMBus SMBus Command Data (See section 2.3 for Details) Function Mode Access Address Code Type D15 D14 D13 D12 D11 D10 D09 D08 D07 D06 D05 D04 D03 D02 D01 D00...
  • Page 16 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 AlertResponse() Slave Read 7-bit: Register see (1) Byte 0001_100b 8-bit: 0×18 (1) Read-byte format. 0×14 is returned as the interrupt address of the LTC1760. 1760fc For more information www.linear.com/LTC1760...

  • Page 17: Description Of Supported Smbus Functions

    Function Name() (command code) Used by the SMBus Host to determine the present state Description: of the LTC1760 and the attached batteries. It also may be A brief description of the function. used to determine the state of the battery system after...

  • Page 18: Batterysystemstatecont() (0×02)

    8-bit address, 0×012, is blocked. The read only CALIBRATE_REQUEST_SUPPORT bit is Purpose: always set high to indicate that the LTC1760 has a mecha- nism to determine when any of the attached batteries are Used by the SMBus Host to retrieve additional state in need of a calibration cycle.

  • Page 19: Batterysysteminfo() (0×04)

    The read only CALIBRATE_REQUEST bit is set whenever The read/write CALIBRATE_BAT[4:1]nibble is used by the the LTC1760 has determined that one or both of the con- SMBus Host to select the battery to be calibrated or to nected batteries need a calibration cycle.

  • Page 20: Ltc() (0×3C)

    2.3.5 BatteryMode() (0×03) The read only BATTERY_SYSTEM_REVISION nibble re- Description: ports the version of the Smart Battery System Manager This function is used by the LTC1760 to read the battery’s specification supported. Mode register. LTC1760 always returns 1000b for this nibble, indicating Purpose: Version 1.0 without optional PEC support.

  • Page 21: Current() (0×0A)

    Description: Allows the LTC1760 to determine the maximum charging voltage. This function is used by the LTC1760 to read the actual current being supplied through the battery terminals. SMBus Protocol: Read Word. LTC1760 reads Battery 1 or Battery 2 as an SMBus Master.

  • Page 22: Alertresponse()

    2.3.11 AlertResponse() The read only TERMINATE_CHARGE_RESERVED bit is Description: used by the LTC1760 to determine if charging may continue. The SMBus Host uses the Alert Response Address (ARA) to Allowed values are: simultaneously address all devices on the SMBus and de- termine which devices are currently asserting SMBALERT.

  • Page 23: Ltc1760 Smbus Controller Operation

    *SMB INCLUDES SCL AND SDA, SMB1 INCLUDES SCL1 AND SDA1, AND SMB2 INCLUDES SCL2 AND SDA2. Figure 1. Switch Configurations Used by the LTC1760 for Managing Dual Port Battery Communication The dual port operation allows the SMBus Host to be an invalid command code is transmitted to the LTC1760.
  • Page 24 LTC1760 OPERATION 1760fc For more information www.linear.com/LTC1760...
  • Page 25 LTC1760 OPERATION 1760fc For more information www.linear.com/LTC1760...

  • Page 26: Ltc1760 Smbalert Operation

    The LTC1760 will attempt to reinitiate wake-up charging on a battery if the battery is not being charged, the therm- The SMBALERT pin allows the LTC1760 to signal to the istor is reporting IDEAL-RANGE, and the battery fails to SMBus Host that there has been a change of status.

  • Page 27: Wake-Up Charging Current And Voltage Limits

    Refer to “Section 6.2”. 6. The SMBus Host asserts BatterySystemStateCont(CHARGING_INHIBIT) high. 5. The battery responds to an LTC1760 Master read of Alarm() with all charge alarms deasserted. 7. Hardware controlled charging inhibit is asserted (MODE low with V high). Refer to “Section 6.2”.

  • Page 28: Controlled Charging Current Programming

    3.6.2 Current Limits When Charging Two Batteries 3.6 Controlled Charging Current Programming (TURBO Mode Disabled) The LTC1760 uses a single charger stage to simultaneously The following additional limits are applied to the charging charge up to two batteries. The batteries are connected to current algorithm described in 3.6 when charging two...

  • Page 29: Current Limits When Charging Two Batteries (Turbo Mode Enabled)

    + 4.1 Turning Off System Power /32. TURBO mode removes this restriction, allowing LIMIT The LTC1760 allows the user to turn off system power using the charger to output as much as I into the combined LIMIT the LTC(POWER_OFF) bit.

  • Page 30: Power-By Algorithm When A Battery Is Being Calibrated

    1. A battery issues a TERMINATE_DISCHARGE alarm and Power Reporting with AC_PRESENT Low and both Batteries Present, as a Function of Power Alarms. AC_PRESENT is high. The LTC1760 will select the other battery and DCIN to power the system. BATTERY 2...

  • Page 31: Initiating Calibration Of Selected Battery

    6 MODE Pin Operation calibration by reading BatteryMode(CONDITION_FLAG). This flag is cached in the LTC1760. The LTC1760 sets The MODE pin is a multifunction pin that allows the LTC1760 BatterySystemStateCont(CALIBRATE_REQUEST) high. to: 1) display charging status in stand alone operation; 2) The LTC1760 will always select the battery that is requesting activate hardware charge inhibit;...

  • Page 32: Hardware Charge Inhibit

    , SDA VDDS IL_VDDS Error amp CA2 compares this current against the desired and SCL are not used and will not interfere with LTC1760 current programmed by the I at the I pin and adjusts battery communication. This feature allows the LTC1760 to...

  • Page 33: Charge Mux Switches

    LTC1760 OPERATION battery voltage, the converter will attempt to turn on the 7.2 Dual Charging top MOSFET continuously (“dropout’’). A dropout timer Note that the charge MUX switch drivers will operate detects this condition and forces the top MOSFET to turn together to allow both batteries to be charged simultane- off, and the bottom MOSFET on, for about 200ns at 40µs...

  • Page 34: Autonomous Powerpath Switching

    , including tolerances) should keep (POWER_OFF) is low and the LOPWR comparator trips, PLUS the LTC1760 operating above the UVLO trip voltage long then all of the switches are turned on (3-Diode mode) enough to perform the short-circuit function when the by the Autonomous PowerPath Controller to ensure that input voltages are greater than 8V.

  • Page 35: The Voltage Dac Block

    LTC1760 OPERATION 9 The Voltage DAC Block modulator and switch convert the I value to a variable resistance equal to 1.25R /1023). In regu- DAC(VALUE) The voltage DAC (V ) is a delta-sigma modulator lation, I is servo driven to the 0.8V reference voltage,...
  • Page 36 Adapter Limiting determines how the charger current is shared. This auto- An important feature of the LTC1760 is the ability to auto- matic steering of current is what allows both batteries to matically adjust charging current to a level which avoids reach their full capacity points at the same time.
  • Page 37 This voltage sets the limit that will be applied *Values shown above are rounded to nearest standard value. Table 1 RCL values take into account LTC1760 C-grade 5% tolerance for to the battery as reported by battery. Since the battery VCL1.
  • Page 38 Selection If the LTC1760 charger is to operate in low dropout mode Two external power MOSFETs must be selected for use with or with a high duty cycle greater than 85%, then the top-...
  • Page 39 LTC1760 APPLICATIONS INFORMATION For thermistors that are COLD-RANGE: DCIN_CHG VCC2_AC1 SAFETY1 SAFETY2 = 4/64 • V /(RXB + R SAFETYX VCC2 VLIM ILIM SMB_BAT1 SMB_BAT2 SMBALERT For thermistors that are IDEAL-RANGE: = 1.3mA + 700µA + 218µA + 218µA +81µA + 81µA = 4/64 •...
  • Page 40 C are used to filter the V delta- sigma modulation frequency components to a level which The power dissipation of the LTC1760 is dependent is essentially DC. C is the primary filter capacitor and upon the gate charge of Q and Q .(Refer to Typical...
  • Page 41 DS(ON) raised to 4Ω with a bead or inductor, only 5% of the cur- available at this time. The need for the LTC1760 voltage rent ripple will flow in the battery. drop regulation only comes into play for parallel battery...
  • Page 42 DRIVE controller. See Figure 10. is the fixed drive current into the gate from the DRIVE LTC1760 and “t” is the time it takes to move that charge to a new state and change the MOSFET conduction mode. PowerPath LOAD Hence time is directly related to Q .
  • Page 43 A) Single Battery Configuration. 5) Remove all components connected to COMP1, V and V pins. LIMIT LIMIT To limit the LTC1760 to a single battery, modify the battery slot to be eliminated as follows: 6) Short I and V to GND. LIMIT...
  • Page 44 The LTC1760 is not itself to make the connection. a safety device. Consult your battery pack manufacturer 8.
  • Page 45 LTC1760 TYPICAL APPLICATIONS PowerPath MUX 0.03 1µF 0.1µF 0.1µF 4.99k LTC1760 PLUS GDCI 100pF BAT1 GDCO 12.7k GB1I BAT2 GB1O GB2I 0.02 GB2O 1.21k DCDIV LOAD LOPWR COMP1 GCH2 280k 49.9k SCH2 20µF 1800pF GCH1 SCH1 49.9k 0.012µF 3.3k BOOST 100pF 0.1µF...
  • Page 46 LTC1760 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTC1760#packaging for the most recent package drawings. FW Package FW Package 48-Lead Plastic TSSOP (6.1mm) 48-Lead Plastic TSSOP (6.1mm) (Reference LTC DWG # 05-08-1651 Rev A) (Reference LTC DWG # 05-08-1651 Rev A) 12.40 – 12.60* (.488 –...
  • Page 47 Revised Circuit Diagram C5 & C7, BAT1, BAT2 added 1760fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- For more information www.linear.com/LTC1760...
  • Page 48 Current Battery Charger Resistor Voltage/Current Programming, AC Adapter Current Limit and SafetySignal Sensor LTC4100 Smart Battery Charger Controller SMBus Rev 1.1 Compliant 1760fc LT 0817 REV C • PRINTED IN USA www.linear.com/LTC1760  LINEAR TECHNOLOGY CORPORATION 2010 For more information www.linear.com/LTC1760...

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