19-1121; Rev 0; 9/96 KIT ATION EVALU E L B A AVAIL Cost-Saving Multichemistry Battery-Charger System The MAX846A is a cost-saving multichemistry batterycharger system that comes in a space-saving 16-pin QSOP. This integrated system allows different battery chemistries (Li-Ion, NiMH or NiCd cells) to be charged using one circuit. In its simplest application, the MAX846A is a standalone, current-limited float voltage source that charges Li-Ion cells. It can also be paired up with a low-cost microcontroller (µC) to build a universal charger capable of charging Li-Ion, NiMH, and NiCd cells. An internal 0.5%-accurate reference allows safe charging of Li-Ion cells that require tight voltage accuracy. The voltage- and current-regulation loops used to control a low-cost external PNP transistor (or P-channel MOSFET) are independent of each other, allowing more flexibility in the charging algorithms. The MAX846A has a built-in 1%, 3.3V, 20mA linear regulator capable of powering the µC and providing a reference for the µC’s analog-to-digital converters. An on-board reset notifies the controller upon any unexpected loss of power. The µC can be inexpensive, since its only functions are to monitor the voltage and current and to change the charging algorithms. ________________________Applications ____________________________Features ♦ ♦ ♦ ♦ Multichemistry Charger System (Li-Ion, NiMH, NiCd) Independent Voltage and Current Loops ±0.5% Internal Reference for Li-Ion Cells Lowers Cost: —Stands Alone or Uses Low-Cost µC —Built-In 1% Linear Regulator Powers µC —Linear Regulator Provides Reference to µC ADCs —Built-In µC Reset —Controls Low-Cost External PNP Transistor or P-Channel MOSFET ♦ Space-Saving 16-Pin QSOP ♦ Charging-Current-Monitor Output ♦ <1µA Battery Drain when Off ______________Ordering Information PART TEMP. RANGE MAX846AC/D 0°C to +70°C MAX846AEEE -40°C to +85°C PIN-PACKAGE Dice* 16 QSOP *Dice are tested at TA = +25°C only. Contact factory for details. Li-Ion Battery Packs Desktop Cradle Chargers Li-Ion/NiMH/NiCd Multichemistry Battery Chargers Cellular Phones __________Typical Operating Circuit 3.5V TO 20V Notebook Computers Hand-Held Instruments __________________Pin Configuration DRV TOP VIEW CS- DCIN 1 VL 2 CCI 3 GND 4 16 DRV CS+ 15 PGND DCIN 14 CS- MAX846A 13 CS+ CCV 5 12 BATT VSET 6 11 ON ISET 7 10 CELL2 OFFV 8 9 QSOP PWROK ISET BATT Li-ION BATTERY MAX846A VL CELL2 CCV GND CCI PGND PWROK ON ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX846A _______________General Description MAX846A Cost-Saving Multichemistry Battery-Charger System ABSOLUTE MAXIMUM RATINGS DCIN, DRV, CS+, CS-, BATT to GND........................-0.3V, +21V PGND to GND.....................................................................±0.3V VL to GND......................................................................-0.3V, 7V IPWROK ................................................................................10mA PWROK, ISET, CCI, CCV, OFFV, VSET, CELL2, ON to GND ............................................-0.3V, VL + 0.3V CS+ to CS-..........................................................................±0.3V VL Short to GND.........................................................Continuous IDRV ...................................................................................100mA Continuous Power Dissipation (TA = +70°C) QSOP (derate 8.3mW/°C above +70°C) ........................667mW Operating Temperature Range MAX846AEEE ....................................................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDCIN = 10V, ON = VL, IVL = IVSET = 0mA, VCS- = VCS+ = 10V, VBATT = 4.5V, VOFFV = VCELL2 = 0V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 5 mA 20.0 V VL REGULATOR DCIN Supply Current VDCIN = 20V, IDRV = IVL = 0mA Operating Range 3.7 Output Voltage 0mA < IVL < 20mA, 3.7V < VDCIN < 20V Short-Circuit Current Limit VL = GND PWROK Trip Level Rising VL edge, 2% hysteresis VL Undervoltage-Lockout Level 3.267 3.305 3.333 50 2.9 3.0 2.5 V mA 3.1 V 2.9 V REFERENCE Output Voltage Measured at VSET, IVSET = 0mA, VON = 0V Output Resistance -0.5% 1.650 +0.5% V -2% 20 +2% kΩ 0.95 1 1.05 mA/V 3 µA 20.0 V CURRENT-SENSE AMPLIFIER Transconductance VISET = 1.7V, VCS+ - VCS- = 165mV Output Offset Current VCS+ = 4V Input Common-Mode Range Measured at VCS-, VCS+ - VCS- = 165mV 2.1 Maximum Differential Input Voltage VCS- = VISET = 2.1V, CSA transconductance >0.9mA/V 225 CS- Lockout Voltage When VCS- is less than this voltage, DRV is disabled. 1.9 CS+, CS- Input Current VCS+ = 20V, VCS+ -VCS- = 165mV CS+, CS- Off Input Current DCIN = VL = ON = GND 2 mV 0.01 _______________________________________________________________________________________ 2.1 V 250 µA 10 µA Cost-Saving Multichemistry Battery-Charger System MAX846A ELECTRICAL CHARACTERISTICS (continued) (VDCIN = 10V, ON = VL, IVL = IVSET = 0mA, VCS- = VCS+ = 10V, VBATT = 4.5V, VOFFV = VCELL2 = 0V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS VOLTAGE LOOP Voltage-Loop Set Point VVSET = 1.650V, VCELL2 = 0V, IDRV = 1mA, VDRV = 10V -0.25% 4.2 +0.25% VVSET = 1.650V, VCELL2 = VL, IDRV = 1mA, MAX846A VDRV = 10V -0.25% 8.4 +0.25% VSET Common-Mode Input Range V 1.25 CCV Output Impedance 2.0 150 Voltage-Loop Load Regulation 1mA < IDRV < 5mA BATT Input Current VBATT = 10V, CELL2 = GND or VL BATT Off Input Current VBATT = 10V, ON = GND, CELL2 = GND or VL V kΩ % 0.05 225 µA 0.01 1 µA 1.650 1.666 V CURRENT LOOP Current-Loop Set Point IDRV = 5mA, VDRV = 10V 1.634 CA Voltage Gain 5 V/V CCI Output Impedance 50 kΩ Overcurrent Trip Level When VISET exceeds this voltage, DRV current is disabled. 1.90 2.1 V DRIVER DRV Sink Current VDRV = 3V DRV Off Current VDRV = 20V, VON = 0V 20 mA 0.1 100 µA VL V LOGIC INPUTS AND OUTPUTS Input High Level CELL2, ON, OFFV 2.4 Input Low Level CELL2, ON, OFFV 0 Input Current CELL2, ON, OFFV PWROK Output Low Level IPWROK = 1mA, VDCIN = VVL = 2.5V PWROK Output High Leakage VPWROK = 3.3V 0.01 0.01 0.8 V 1 µA 0.4 V 1 µA _______________________________________________________________________________________ 3 MAX846A Cost-Saving Multichemistry Battery-Charger System ELECTRICAL CHARACTERISTICS (Note 1) (VDCIN = 10V, ON = VL, IVL = IVSET = 0mA, VCS- = VCS+ = 10V, VBATT = 4.5V, VOFFV = VCELL2 = 0V, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS 5 mA 3.259 3.341 V 2.9 3.1 V 2.5 3.0 V VL REGULATOR DCIN Supply Current VDCIN = 20V, IDRV = IVL = 0mA Output Voltage 0mA < IVL < 20mA, 3.7V < VDCIN < 20V PWROK Trip Level Rising VL edge, 2% hysteresis VL Undervoltage-Lockout Level REFERENCE Output Voltage Measured at VSET, IVSET = 0mA, VON = 0V Output Resistance -0.7% 1.650 +0.7% V -2% 20 +2% kΩ CURRENT-SENSE AMPLIFIER Transconductance VISET = 1.7V, VCS+ - VCS- = 165mV 1.07 mA/V Output Offset Current VCS+ = 4V 0.93 5 µA CS+, CS- Off Input Current VON = 0V, VCS+ = VCS- = 10V 10 µA VOLTAGE LOOP Voltage-Loop Set Point BATT Off Input Current VVSET = 1.650V, VCELL2 = 0V, IDRV = 1mA, MAX846A VDRV = 10V -0.35% 4.2 +0.35% VVSET = 1.650V, VCELL2 = VL, IDRV = 1mA, VDRV = 10V -0.35% 8.4 +0.35% V VBATT = 10V, ON = GND, CELL2 = GND or VL 1 µA CURRENT LOOP Current-Loop Set Point IDRV = 5mA, VDRV = 10V 1.625 1.675 V Overcurrent Trip Level When VISET exceeds this voltage, DRV current is disabled. 1.86 2.14 V DRIVER DRV Sink Current VDRV = 3V DRV Off Current VDRV = 20V, ON = GND 20 Note 1: Specifications to -40°C are guaranteed by design and not production tested. 4 _______________________________________________________________________________________ mA 100 µA Cost-Saving Multichemistry Battery-Charger System BATTERY INPUT CURRENT vs. BATTERY VOLTAGE CURRENT-SENSE AMPLIFIER TRANSCONDUCTANCE vs. ISET VOLTAGE 80 CELL2 = VL 70 ∆V = 100mV 1.015 ∆V = 165mV 1.010 1.005 1.000 ∆V = 200mV 0.995 CELL2 = GND 60 82kΩ 50 128kΩ ON 40 30 20 OFF 10 ∆V = 250mV 0 0.990 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 1 2 3 GAIN 150 30 120 20 90 10 40 60 30 30 20 0 10 -30 PHASE 8 9 10 -40 -50 -20 -120 1M -60 1k 10k 100k FREQUENCY (Hz) 60 GAIN 30 0 = - Charging at 100mA = -Charging at 200mA 2 Li-Ion Cells CCCV = 10nF COUT = 4.7µF TIP2955 PNP PASS TRANSISTOR -30 -90 120 90 -20 -60 180 150 PHASE 0 -10 100 7 MAX846-04 -10 0 10 100 1k 10k 100k FREQUENCY (Hz) -30 -60 -90 --120 1M Li-ION CHARGING PROFILE MAX846-04 900 9.0 8.8 700 BATTERY VOLTAGE 8.6 8.4 600 8.2 500 8.0 400 7.8 300 7.6 200 7.4 CHARGING CURRENT 100 BATTERY VOLTAGE (V) 800 CHARGING CURRENT (mA) 10 6 PHASE (DEGREES) 60 40 GAIN (dB) CCCI = 10nF 180 PHASE (DEGREES) MAX846-03 50 5 VOLTAGE-LOOP GAIN CURRENT-LOOP GAIN 80 70 4 BATT VOLTAGE (V) ISET VOLTAGE (V) GAIN (dB) CSA GM (mA/V) 1.025 1.020 MAX846-02 ∆V = VCS+ - VCS- BATT INPUT CURRENT (µA) 1.030 MAX846-01 1.035 7.2 0 7.0 0 60 120 180 240 TIME (MINUTES) _______________________________________________________________________________________ 5 MAX846A __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX846A Cost-Saving Multichemistry Battery-Charger System ______________________________________________________________Pin Description PIN NAME FUNCTION 1 DCIN 2 VL 3.3V, 20mA, 1% Linear-Regulator Output. VL powers the system µC and other components. Bypass to GND with a 4.7µF tantalum or ceramic capacitor. 3 CCI Current-Regulation-Loop Compensation Pin. Connect a compensation capacitor (typically 10nF) from CCI to VL. 4 GND Ground 5 CCV Voltage-Regulation-Loop Compensation Pin. Connect a compensation capacitor (typically 10nF) from CCV to VL. 6 VSET Float-Voltage Reference-Adjust Input. Leave VSET open for a 4.2V default. See the Applications Information section for adjustment information. 7 ISET Current-Set Input/Current-Monitor Output. ISET sets the current-regulation point. Connect a resistor from ISET to GND to monitor the charging current. ISET voltage is regulated at 1.65V by the currentregulation loop. To adjust the current-regulation point, either modify the resistance from ISET to ground or connect a fixed resistor and adjust the voltage on the other side of the resistor (Figure 5). The transconductance of the current-sense amplifier is 1mA/V. 8 OFFV Logic Input that disables the voltage-regulation loop. Set OFFV high for NiCd or NiMH batteries. 9 PWROK Open-Drain, Power-Good Output to µC. PWROK is low when VL is less than 3V. The reset timeout period can be set externally using an RC circuit (Figure 3). 10 CELL2 Digital Input. CELL2 programs the number of Li-Ion cells to be charged. A high level equals two cells; a low level equals one cell. 11 ON 12 BATT Battery Input. Connect BATT to positive battery terminal. 13 CS+ Current-Sense Amplifier High-Side Input. Connect CS+ to the sense resistor’s power-source side. The sense resistor may be placed on either side of the pass transistor. 14 CS- Current-Sense Amplifier Low-Side Input. Connect CS- to the sense resistor’s battery side. 15 PGND 16 DRV Supply Input from External DC Source. 3.7V ≤ VDCIN ≤ 20V. Charger ON/OFF Input. When low, the driver section is turned off and IBATT <1µA. The VL regulator is always active. Power Ground External Pass Transistor (P-channel MOSFET or PNP) Base/Gate Drive Output. DRV sinks current only. _______________Detailed Description The MAX846A battery-charging controller combines three functional blocks: a 3.3V precision, low-dropout linear regulator (LDO), a precision voltage reference, and a voltage/current regulator (Figure 1). Linear Regulator The LDO regulator output voltage (VL) is two times the internal reference voltage; therefore, the reference and LDO track. VL delivers up to 20mA to an external load and is short-circuit protected. The power-good output (PWROK) provides microcontroller (µC) reset and charge-current inhibition. 6 Voltage Reference The precision internal reference provides a voltage to accurately set the float voltage for lithium-ion (Li-Ion) battery charging. The reference output connects in series with an internal, 2%-accurate, 20kΩ resistor. This allows the float voltage to be adjusted using one external 1% resistor (R VSET ) to form a voltage divider (Figure 4). The float-voltage accuracy is important for battery life and to ensure full capacity in Li-Ion batteries. Table 1 shows the accuracies attainable using the MAX846A. _______________________________________________________________________________________ Cost-Saving Multichemistry Battery-Charger System Stability The Typical Operating Characteristics show the loop gains for the current loop and voltage loop. The dominant pole for each loop is set by the compensation capacitor connected to each capacitive compensation pin (CCI, CCV). The DC loop gains are about 50dB for the current loop and about 33dB for the voltage loop, for a battery impedance of 250mΩ. The CCI output impedance (50kΩ) and the CCI capacitor determine the current-loop dominant pole. In Figure 2, the recommended CCCV is 10nF, which places a dominant pole at 300Hz. There is a high-frequency pole, due to the external PNP, at approximately fT/ß. This pole frequency (on the order of a few hundred kilohertz) will vary with the type of PNP used. Connect a 10nF capacitor between the base and emitter of the PNP to prevent self-oscillation (due to the high-impedance base drive). Similarly, the CCV output impedance (150kΩ) and the CCV capacitor set the voltage-loop dominant pole. In Figure 2, the compensation capacitance is 10nF, which places a dominant pole at 200Hz. The battery impedance directly affects the voltage-loop DC and high-frequency gain. At DC, the loop gain is proportional to the battery resistance. At higher frequencies, the AC impedance of the battery and its connections introduces an additional high-frequency zero. A 4.7µF output capacitor in parallel with the battery, mounted close to BATT, minimizes the impact of this impedance. The effect of the battery impedance on DC gain is noticeable in the Voltage-Loop-Gain graph (see Typical Operating Characteristics). The solid line represents voltage-loop gain versus frequency for a fully charged battery, when the battery energy level is high and the ESR is low. The charging current is 100mA. The dashed line shows the loop gain with a 200mA charging current, a lower amount of stored energy in the battery, and a higher battery ESR. __________Applications Information Stand-Alone Li-Ion Charger Figure 2 shows the stand-alone configuration of the MAX846A. Select the external components and pin configurations as follows: • Program the number of cells: Connect CELL2 to GND for one-cell operation, or to VL for two-cell operation. • Program the float voltage: Connect a 1% resistor from VSET to GND to adjust the float voltage down, or to VL to adjust it up. If VSET is unconnected, the float voltage will be 4.2V per cell. Let the desired float voltage per cell be VF, and calculate the resistor value as follows: Table 1. Float-Voltage Accuracy ERROR SOURCE ERROR Internal-reference accuracy ±0.5% VSET error due to external divider. Calculated from a 2% internal 20kΩ resistor tolerance and a 1% external RVSET resistor tolerance. The total error is 3% x (adjustment). Assume max adjustment range of 5%. ±0.15% VSET amplifier and divider accuracy ±0.25% TOTAL ±0.9% _______________________________________________________________________________________ 7 MAX846A Voltage/Current Regulator The voltage/current regulator consists of a precision attenuator, voltage loop, current-sense amplifier, and current loop. The attenuator can be pin programmed to set the regulation voltage for one or two Li-Ion cells (4.2V and 8.4V, respectively). The current-sense amplifier is configured to sense the battery current on the high side. It is, in essence, a transconductance amplifier converting the voltage across an external sense resistor (RCS) to a current, and applying this current to an external load resistor (RISET). Set the charge current by selecting RCS and RISET. The charge current can also be adjusted by varying the voltage at the low side of RISET or by summing/subtracting current from the ISET node (Figure 5). The voltage and current loops are individually compensated using external capacitors at CCV and CCI, respectively. The outputs of these two loops are OR’ed together and drive an open-drain, internal N-channel MOSFET transistor sinking current to ground. An external P-channel MOSFET or PNP transistor pass element completes the loop. MAX846A Cost-Saving Multichemistry Battery-Charger System DC INPUT (OR P-CHANNEL) 3.5V TO 20V 0.01µF RDRV 660Ω DCIN 3.3V TO µC VL 3.3V, 1% LDO 4.7µF DRV CS+ PGND GND OR DAC RCS 165mΩ IBATT 1k BST N CSA CS- ISET 10k VL TO ADC 2V CL VL 5nF CCI 1.65V CA VL 5nF CCV BATT Li OR Ni VA VA 4.7µF 2 Li 1 Li OFF CELL2 N OFFV ON OPEN OR DAC RVSET VSET 400k, 1% (±5% ADJ) 20k, 2% 1.65V, 0.5% REF N VL REFOK GND CS- > 2V DRV ENABLE PWROK MAX846A VL > 3V ON ON OFF Figure 1. Functional Diagram 8 _______________________________________________________________________________________ TO µC Cost-Saving Multichemistry Battery-Charger System BATT DCIN 3.7V TO 20V RCS MAX846A (0.165V ) I EXTERNAL PASS TRANSISTOR CAN BE EITHER PNP OR PMOS FET. 10nF 4.7µF RDRV 660Ω CS+ CS- DRV VL BATT RVSET ADJUST (UP) VSET DCIN (DOWN) VL MAX846A 100k 10k PWROK ISET RISET ON 0.01µF CCI VL CCV (2 CELLS) 0.01µF CELL2 OFFV (1 CELL) 4.7µF GND PGND Figure 2. Stand-Alone Li-Ion Charger RVSET = 20kΩ 4.2 VX − VF 1.65 VF − 4.2 where VX is either GND or VL, and VF is the per-cell float voltage. In the circuit of Figure 1, R VSET is 400kΩ. RVSET and the internal 20kΩ resistor form a divider, resulting in an adjustment range of approximately ±5%. The current-regulation loop attempts to maintain the voltage on ISET at 1.65V. Selecting resistor RISET determines the reflected voltage required at the currentsense amplifier input. • Calculate RCS and RISET as follows: RCS = VCS / IBATT RISET (in kΩ) = 1.65V / VCS where the recommended value for VCS is 165mV. • Connect ON to PWROK to prevent the charge current from turning on until the voltages have settled. Minimize power dissipation in the external pass transistor. Power dissipation can be controlled by setting the DCIN input supply as low as possible, or by making VDCIN track the battery voltage. Microprocessor-Controlled Multichemistry Operation The MAX846A is highly adjustable, allowing for simple interfacing with a low-cost µC to charge Ni-based and Li-Ion batteries using one application circuit (Figure 3). _______________________________________________________________________________________ 9 MAX846A Cost-Saving Multichemistry Battery-Charger System P DCIN 3.7V TO 20V Li OR Ni CS+ CS- DRV BATT DCIN ADC (MEASURE V(BATT)) CCI CCV MAX846A ON CELL2 I/O (LOW = TURN OFF CHARGE) I/O (HIGH = 2 Li CELLS) OFFV I/O (HIGH = DISABLE FLOAT V) VSET PWM/DAC (CONTROL FLOAT V) ISET PWM/DAC (CONTROL CHARGE I) ADC (MEASURE IBATT) GND VL VDD MICROCONTROLLER PGND PWROK RST Figure 3. Desktop Multichemistry Charger Concept Component selection is similar to that of stand-alone operation. By using DACs or µC PWM outputs, the float voltage and charging current can be adjusted by the µC. When a Ni-based battery is being charged, disable the float-voltage regulation using the OFFV input. The µC can also monitor the charge current through the battery by reading the ISET output’s voltage using its ADC. Similarly, the battery voltage can be measured using a voltage divider from the battery. Note that the µC only needs to configure the system for correct voltage and current levels for the battery being charged, and for Ni-based batteries to detect end-ofcharge and adjust the current level to trickle. The controller is not burdened with the regulation task. 10 Float-voltage accuracy is important for battery life and for reaching full capacity for Li-Ion batteries. Table 1 shows the accuracy attainable using the MAX846A. For best float-voltage accuracy, set the DRV current to 1mA (RDRV = 660Ω for a PNP pass transistor). High-Power Multichemistry Offline Charger The circuit in Figure 6 minimizes power dissipation in the pass transistor by providing optical feedback to the input power source. The offline AC/DC converter maintains 1.2V across the PNP. This allows much higher charging currents than can be used with conventional power sources. ______________________________________________________________________________________ Cost-Saving Multichemistry Battery-Charger System MAX846A 20k 400k VSET 1.65V 0 TO VL 20k VSET 1.65V DAC 2% 0 2% 1% MAX846A MAX846A 100% µC PWM OUTPUT 400k 1% n WITH VOLTAGE OUTPUT DAC WITH PWM FROM MICROCONTROLLER Figure 4. VSET Adjustment Methods MAX846A MAX846A 20k ISET 0 ISET DAC 20k 10k 10k 100% µC PWM OUTPUT 20k n WITH VOLTAGE OUTPUT DAC WITH PWM FROM MICROCONTROLLER Figure 5. ISET Adjustment Methods OPTO-COUPLER FEEDBACK AC/DC CONVERTER MAX846 MICRO CONTROLLER Figure 6. Low-Cost Desktop Multichemistry Charger Concept ______________________________________________________________________________________ 11 MAX846A Cost-Saving Multichemistry Battery-Charger System ___________________Chip Topography VL DCIN DRV PGND CS- CCI CS+ GND 0.105" (2.67mm) BATT CCV VSET ON ISET OFFV PWROK CELL2 0.085" (2.165mm) SUBSTRATE CONNECTED TO GND TRANSISTOR COUNT: 349 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.