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bq2057/C/W/T
Advanced Li-Ion Linear Charge Management IC
Features
Ideal for single- and dual-cell Li-Ion packs with coke or graphite anodes 0.3V dropout voltage AutoCompTM dynamic compensation of battery pack's internal impedance Optional temperature-monitoring before and during charge Integrated voltage and current regulation with programmable c h a r g e - c u r r e n t a n d high- or low-side current sensing Integrated cell conditioning for reviving deeply discharged cells and minimizing heat dissipation during initial stage of charge Better than 1% voltage regulation accuracy Charge status output for LED or host processor interface Automatic battery-recharge feature Charge termination by minimum current Low-power sleep mode Packaging: 8-pin SOIC, 8-pin TSSOP
General Description
The BENCHMARQ bq2057 series advanced Li-Ion l i n e a r chargemanagement ICs are designed for cost-sensitive and compact portable electronics. They combine highaccuracy c u r r e n t a n d voltage regulation, battery conditioning, t e m p e r a t u r e monitoring, charge termination, charge-status indication, and AutoComp charge-rate compensation in a single 8-pin IC. The bq2057 continuously measures battery temperature using an external thermistor. For safety reasons, the bq2057 inhibits charge until the battery temperature is within user-defined thresholds. The bq2057 then charges the battery in three phases: conditioning, constant current, and constant voltage. If the battery voltage is below the low-voltage t h r e s h o l d VM I N , t h e bq2057 trickle-charges to condition the battery. The conditioning charge rate is set at approximately 10% of the regulation current. The conditioning current also minimizes heat dissipation in the external pass-element during the initial stage of charge. After conditioning, the bq2057 applies a constant current to the battery. An external sense-resistor sets the magnitude of the current. The sense-resistor can be on either the
low or the high side of the battery without additional components. The constant-current phase continues until the battery reaches the charge-regulation voltage. The bq2057 then begins the constant-voltage phase. The accuracy of the voltage regulation is better than 1% over the operating-temperature and supply-voltage ranges. For single and dual cells with either coke or graphite anodes, the bq2057 is offered in four fixed-voltage versions: 4.1V, 4.2V, 8.2V, and 8.4V. Charge stops when the current tapers to the charge termination threshold, VTERM. The bq2057 automatically restarts the charge if the battery voltage falls below the VRCH threshold. The designer also may u s e t h e AutoComp feature to reduce charging time. This proprietary technique allows safe and dynamic compensation for the internal impedance of the battery pack during charge. Available Options Charge Regulation Voltage 4.1V 4.2V 8.2V 8.4V
Part Number bq2057 bq2057C bq2057T bq2057W
Pin Connections
Pin Names
SNS BAT VCC TS Current-sense input Battery-voltage input Supply voltage Temperature sense input STAT VSS CC COMP Charge status output Ground input Charge control output Charge-rate compensation input
SLUS025B-JANUARY2000-REVISED JUNE 2000
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bq2057
Pin Descriptions
SNS Current-sense input Battery current is sensed via the voltage developed on this pin by an external sense resistor. BAT Battery voltage input Voltage sense-input tied directly to the positive side of the battery. VCC TS VCC supply input Temperature sense input Input for an external battery-temperature monitoring circuit. Connecting this input to Vcc/2 disables this feature. COMP VSS CC STAT Charge status output Tri-state indication of charge-in-progress, charge-complete, and temperature fault. Ground input Charge-control output Source-follower output that drives an external pass-transistor for current and voltage regulation. Charge-rate compensation input Sets the charge-rate compensation level. The voltage-regulation o u t p u t may be programmed to vary as a function of the charge current delivered to the battery.
VSS
VCC
BAT
POWER ON RESET
CC
COMP
KCOMP
VREG CONTROL BLOCK VCC
SNS VSNS LED STAT STAT
TS VTS1, VTS2
2057FBD.eps
Figure 1. Functional Block Diagram
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bq2057
Sleep Mode LED = Hi-Z
NO
VCC > VBAT
YES
YES
Temperature Check TS > VTS1 TS < VTS2
NO
Temperature Fault LED = Hi-Z
VBAT VMIN
YES
Conditioning Phase LED = High
NO
Current Regulation Phase LED = High
Voltage Regulation Phase LED = HIGH Charge Complete LED = LOW
NO
IBAT
IREG 10
YES
VBAT VRCH
YES
2057OFC.eps
NO
Figure 2. Operational Flow Chart
Functional Description
Figure 1 is a functional block diagram, Figure 2 an operational flow chart, and Figure 3 a typical charger schematic for the bq2057.
Charge Qualification and Conditioning
When power is applied, the bq2057 starts a charge-cycle if a battery is already present or when a battery is in-
serted. Charge qualification is based on battery temperature and voltage. The bq2057 suspends charge if the battery temperature is outside the VTS1 to VTS2 range and suspends charge until the battery temperature is within the allowed range. The bq2057 also checks the battery voltage. If the battery voltage is below the low-voltage t h r e s h o l d VM I N , t h e bq2057 u s e s trickle-charge to condition the battery. The conditioning charge rate I COND is set at approximately 10% of the regulation current. The conditioning current also mini-
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bq2057
RSNS 0.2 DC+
Q1 FZT788B
D2 PACK+
R1 1k
C1 0.1F VCC PACKVCC NTC
7 1 3 6 DCC2 0.1F
CC
bq2057 COMP BAT TS STAT
8 2 4 5 D1 RT2 R2 2k RT1 TEMP Battery Pack
SNS VCC VSS
2057ldc.eps
Figure 3. Low-Dropout Single- or Dual-Cell Li-Ion Charger
mizes heat dissipation in the external pass-element during the initial stage of charge. See Figure 4 for a typical charge-algorithm. either coke or graphite anodes: 4.1V, 4.2V, 8.2V, and 8.4V. Other regulation voltages can be achieved by adding a voltage divider between the positive and negative terminals of the battery pack. The voltage divider presents a scaled battery pack voltage to BAT input. (See Figures 7 and 8.) The resistor values RB1 and RB2 for the voltage divider are calculated by the following equation: RB1 VCELL -1 = N RB2 VREG where N = Number of cells in series VCELL = Desired regulation voltage per cell
Current Regulation
The bq2057 regulates current while the battery-pack voltage is less than the regulation voltage, VREG. The bq2057 monitors charge current at the SNS input by the voltage drop across a sense-resistor, RSNS, in series with the battery pack. In high-side current sensing configuration (Figure 5), RSNS is placed between the Vcc and SNS pins, and in low-side sensing (Figure 6) the RSNS is placed between Vss (battery negative) and SNS (charger ground) pins. Charge-current feedback, applied through pin SNS, maintains regulation around a threshold of VSNS. The following formula calculates the value of the sense resistor: RSNS = VSNS IREG
Charge Termination and Re-Charge
The bq2057 monitors the charging current during the voltage-regulation phase. The bq2057 declares a "batterycomplete" condition and terminates charge when the current tapers off to the charge termination threshold, VTERM. A new charge cycle begins when the battery voltage falls below the VRCH threshold.
where I REG is the desired charging current.
Voltage Monitoring and Regulation
Voltage regulation feedback is through pin BAT. This input is tied directly to the positive side of the battery pack. The bq2057 monitors the battery-pack voltage between the BAT and VSS pins. The bq2057 is offered in four fixed-voltage versions for single- and dual-cells with
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bq2057
Low-Current Conditioning Phase
Current Regulation Phase
Voltage Regulation Phase (Shown with the optional AutoComp feature)
VPACK VREG IREG
VMIN
VBAT
IBAT ICOND = IREG 10
GR2057b.eps
IFULL = IREG 10
Figure 4. Typical Charge Algorithm
DC+
DC+ RSNS
BAT+
BAT+ bq2057
bq2057 1 2 3 4 DCSNS BAT VCC TS COMP CC VSS STAT 8 7 6 5
DC-
1 2 3 4
SNS BAT VCC TS
COMP CC VSS STAT
8 7 6 5 BAT-
RSNS BAT2057HSCS.eps
2057LSCS1.eps
Figure 5. High-Side Current Sensing
Figure 6. Low-Side Current Sensing
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bq2057
DC+
DC+ RSNS BAT+ RB1
bq2057 1 2 3 4 SNS BAT VCC TS COMP CC VSS STAT 8 7 6 5 RB2 RB1
BAT+
bq2057 DC1 2 3 4 SNS BAT VCC TS COMP CC VSS STAT 8 7 6 5 RB2 BAT-
DC-
BATRSNS
2057OVDHSC.eps
2057OVDLSC.eps
Figure 7. Optional Voltage Divider for Non-Standard Regulation Voltage, (High-Side Current Sensing) Temperature Monitoring
The bq2057 continuously monitors temperature by measuring the voltage between the TS and VSS pins. A negative- or a positive-temperature coefficient thermistor (NTC, PTC) and an external voltage-divider typically develop this voltage. (See Figure 9.) The bq2057 compares this voltage against its internal VTS1 and VTS2 thresholds to determine if charging is allowed. (See Figure 10.) The temperature sensing circuit is immune to any fluctuation in the VCC, since both the external voltage divider and the internal thresholds (VTS1 and VTS2) are referenced to VCC.
DC+ RSNS BAT+
Figure 8. Optional Voltage Divider for Non-Standard Regulation Voltage, (Low-Side Current Sensing)
The resistor values of RT1 and RT2 are calculated by the following equations: For NTC thermistors
(5 RTH RTC) RT1 = ( 3 (RTC - RTH ) ) (5 RTH RTC) RT2 = (( 2 RTC) - (7 RTH ) )
DC+ BAT+ bq2057 RT1 bq2057 1 2 3 4 SNS BAT VCC TS COMP CC VSS STAT 8 7 6 5 DCRT2 BATBATRSNS 1 2 3 4
SNS BAT COMP 8 CC 7
SS STAT 5
DC-
VCC
TS
V
6 RT1 Thermistor
RT2
Thermistor
High-Side Current Sensing
2057TSC.eps
Low-Side Current Sensing
Figure 9. Temperature Sensing Circuits
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bq2057
V CC
Condition Battery conditioning and charging Charge complete Temperature fault or sleep mode
STAT Pin High Low High-Z
Temp Fault V TS2 Normal Temp Range V TS1
Automatic Charge-Rate Compensation
To reduce charging time, the bq2057 uses the proprietary AutoComp technique to compensate safely for internal impedance of the battery pack. Figure 11 outlines the major components of a single-cell Li-Ion battery pack. The Li-Ion battery pack consists of a cell, protection circuit, fuse, connector, current sense-resistors, and some wiring. Each of these components contains some resistance. Total impedance of the battery pack is the sum of the minimum resistances of all battery-pack components. Using the minimum resistance values reduces the odds for overcompensating. Overcompensating may activate the safety circuit of the battery pack. Compensation is through input pin COMP (Figure 12). A portion of the current-sense voltage, presented through this pin, is scaled by a factor of KCOMP and summed with the regulation threshold, VREG. This process increases the output voltage to compensate for the battery pack's internal impedance and for undesired voltage drops in the circuit.
Temp Fault
V SS
2057TSIT.eps
Figure 10. bq2057 TS Input Thresholds
For PTC thermistors 5 RTH RTC RT1 = ( 3 (RTH -RTC) )
(5 RTH RTC) RT2 = (( 2 RTH ) - (7 RTC) )
where RTC is the cold-temperature resistance and RTH is the hot-temperature resistance of the thermistor, as specified by the thermistor manufacturer. RT1 or RT2 can be omitted if only one temperature setting (Hot or Cold) is required. Applying a voltage between the VTS1 and VTS2 thresholds to pin TS disables the temperature-sensing feature.
Terminal BAT+
R2 FUSE
Wire
Cell Protection Controller
Low-Power Mode
The bq2057 enters the sleep mode if the VCC falls below the voltage at the BAT input. This feature prevents draining the battery pack during the absence of VCC.
Terminal BATDischarge Wire
Wire Charge
Wire
Charge Status Display
The bq2057 reports the status of the charger on the tri-state STAT pin. The three states include "charge in progress, charge complete, and temperature fault.
2057SCLIP.eps
Figure 11. Typical Components of a Single-Cell Li-Ion Pack
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bq2057
DC+ DC+ BAT+ RCOMP2 RCOMP1 DCRSNS bq2057 1 SNS COMP 2 BAT CC 3V VSS CC 4 STAT TS DC8 7 6 5 1 2 3 4 bq2057 SNS COMP BAT CC VSS VCC STAT TS RCOMP1 RSNS RCOMP2 8 7 6 5 BAT+
BATHigh-Side Current Sensing Low-Side Current Sensing
2057AC.eps
Figure 12. AutoComp Circuits
AutoComp setup requires the following information: Total impedance of battery pack (ZPACK) Maximum charging current (IREG) The voltage drop VZ across the internal impedance of the battery pack can then be calculated by VZ = ZPACK I REG The required compensation is then calculated using the following equations: VCOMP = VZ KCOMP where VCOMP is the voltage on COMP pin. This voltage is referenced to Vcc in high-side current-sensing configuration and to Vss for low-side sensing. VPACK is the voltage across the battery pack. The values of RCOMP1 and RCOMP2 can be calculated using the following equation: VCOMP RCOMP2 = VSNS RCOMP1 + RCOMP2
VPACK = VREG + (KCOMP VCOMP)
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bq2057
Absolute Maximum Ratings
Symbol VCC VT TOPR TSTG PD Parameter VCC relative to VSS VCC relative to VSS Operating ambient temperature Storage temperature Power dissipation Min. -0.3 -0.3 -20 -40 Max. +18 VCC + 0.3 70 125 300 Units V V C C mW DC voltage applied on any pin (excluding VCC) Notes
DC Thresholds (TA=TOPR and VCC = 4.5-15V unless otherwise specified)
Symbol Parameter Rating 4.10 VREG 4.20 Voltage regulation reference 8.20 8.40 105 110 VSNS Current regulation reference 125 130 3.0 VMIN Conditioning voltage reference 3.1 6.1 6.3 KCOMP VTS1 VTS2 VRCH VRCH VTERM Notes: AutoComp gain Lower temperature threshold Upper temperature threshold Recharge threshold Recharge threshold Charge termination reference 2.2 0.3 VCC 0.6 VCC VREG - 0.1 VREG - 0.2 -14 10% 10% 2% 2% 2% 2% 15% 3% of VCC 3% of VCC 2% 2% 10mV mV mV V V V V V/V V V V V mV For bq2057T and bq2057W only; see Note 2 For bq2057T and bq2057W only, see Note 4 For bq2057 only For bq2057C only For bq2057T only For bq2057W only See Notes 1, 5 Voltage at pin TS, relative to VSS Voltage at pin TS, relative to VSS Voltage on BAT pin, bq2057 and bq2057C only Voltage on BAT pin, bq2057T and bq2057W only See Note 6 Tolerance 1% 1% 1% 1% 10% 10% Unit V V V V mV mV Notes For bq2057 only; see Notes 1, 2, 3 For bq2057C only; see Notes 1, 2, 3 For bq2057T only; see Notes 1, 2, 3 For bq2057W only; see Notes 1, 2, 3 For bq2057 and bq2057C only; see Note 2 For bq2057 and bq2057C only; see Note 4
1. VCC = VBAT + 0.3V to 15V 2. For high-side current-sensing configuration 3. For low-side current sensing configuration, the tolerance is 1% for TA = 25 and 1.2% for TA = TOPR. 4. For low-side current-sensing configuration 5. 2.4 and 15% for bq2057T and bq2057W in low-side current sensing configuration 6. Voltage at pin SNS, relative to VCC for high-side sensing, and to VSS for low-side sensing, 0C TA 50C
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bq2057
DC Electrical Characteristics (TA= TOPR, and VCC = 4.5 - 15V unless otherwise specified))
Symbol VCC I CC I CCS VOL VOH Parameter Supply voltage Operating current Sleep current Output-low voltage Output-high voltage VCC - 0.5 I IH Input leakage current I SNK VOLCC Sink current CC pin output-low voltage 5 5 40 1.5 0.4 10 0.6 1 Min 4.5 Typical 2 3 Max 15 4 6 Units V mA A A V V A A mA V Excluding external loads For bq2057 and bq2057C, see note For bq2057T and bq2057W, see note I OL = 10mA; STAT pin I OH = 5mA; STAT pin BAT input, VBAT = VREG SNS, COMP, and TS inputs, VSNS = VCOMP = VTS = 5V CC pin, not to exceed P D specification At I SNK (minimum) Notes
Note: VBAT VMIN, VBAT - VCC 0.8V, -20C TA 70C.
Ordering Information
bq2057
Package Option: SN = 8-pin narrow SOIC TS = 8-pin TSSOP Device: bq2057 Advanced Li-Ion Linear Charger for One Cell (4.1V) bq2057C Advanced Li-Ion Linear Charger for One Cell (4.2V) bq2057T Advanced Li-Ion Linear Charger for Two Cells (8.2V) bq2057W Advanced Li-Ion Linear Charger for Two Cells (8.4V)
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bq2057
8-Pin SOIC Narrow (SN)
8-Pin SN (0.150" SOIC)
Inches Dimension A A1 B C D E e H L Min. 0.060 0.004 0.013 0.007 0.185 0.150 0.045 0.225 0.015 Max. 0.070 0.010 0.020 0.010 0.200 0.160 0.055 0.245 0.035 Millimeters Min. 1.52 0.10 0.33 0.18 4.70 3.81 1.14 5.72 0.38 Max. 1.78 0.25 0.51 0.25 5.08 4.06 1.40 6.22 0.89
TS: 8-Pin TSSOP
Dimension A A1 B C D E e H 0.002 0.007 0.004 0.114 0.169 0.246 Inches Min. Max. 0.043 0.006 0.012 0.007 0.122 0.176 0.256 Millimeters Min. 0.05 0.18 0.09 2.90 4.30 6.25 Max. 1.10 0.15 0.30 0.18 3.10 4.48 6.50
0.0256BSC
0.65BSC
Notes: 1. Controlling dimension: millimeters. Inches shown for reference only. 2 'D' and 'E' do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15mm per side 3 Each lead centerline shall be located within 0.10mm of its exact true position. 4. Leads shall be coplanar within 0.08mm at the seating plane. 5 Dimension 'B' does not include dambar protrusion. The dambar protrusion(s) shall not cause the lead width to exceed 'B' maximum by more than 0.08mm. 6 Dimension applies to the flat section of the lead between 0.10mm and 0.25mm from the lead tip. 7 'A1' is defined as the distance from the seating plane to the lowest point of the package body (base plane).
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Copyright (c)
2000, Texas Instruments Incorporated

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