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19-1605; Rev 0; 1/00
Lithium-Ion Battery Pack Protector
General Description
The MAX1665 provides protection against overvoltage, undervoltage, overcharge current, and overdischarge current for 2-cell to 4-cell lithium-ion (Li+) battery packs. Very low operating current ensures that cells are not overdischarged during long storage periods. The MAX1665 controls two external N-channel MOSFETs to limit the charge and discharge voltages. Charging is allowed when the per-cell voltage is below +4.3V. When the voltage on any cell rises above +4.3V (overvoltage limit), the MAX1665 turns off the charge MOSFET. This safety feature prevents overcharge of any cell within the battery pack. Discharge is allowed when the per-cell voltage is above +2.5V (undervoltage limit). If the voltage across any cell falls below +2.5V, the MAX1665 turns off the discharge MOSFET. This safety feature prevents overdischarge of any cell within the battery pack. Charging and discharging are allowed if the voltage between PKN and BN is less than 250mV. This safety feature prevents excessive pack current.
PART MAX1665SESA MAX1665VESA MAX1665XESA
____________________________Features
o Complete Protection Against: Cell Overvoltage Cell Undervoltage o Pack Protection for Excessive Charge and Discharge o Very Low Supply Current: 16A typ o Low Standby Current: 1A max o Matched Cell Input Bias Current (<500pA) Preserves Cell Balance
MAX1665S/V/X
Ordering Information
TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 8 SO 8 SO 8 SO CELL COUNT 2 3 4
Applications
Lithium-Ion Battery Packs
Typical Operating Circuit
TOP VIEW
(+) I.C. (B4P) 1 DSG 2 B4P B3P CHG DSG B2P PKN 3 4
Pin Configuration
8 7
I.C. [B3P] B2P B1P BN
MAX1665S MAX1665V MAX1665X
6 5
MAX1665X
CHG B1P BN (-) PKN
SO
NOTES: I.C. = INTERNAL CONNECTION. MAKE NO CONNECTIONS TO THIS PIN. ( ) ARE FOR THE MAX1665X. [ ] ARE FOR THE MAX1665V AND MAX1665X.
________________________________________________________________ Maxim Integrated Products
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
ABSOLUTE MAXIMUM RATINGS
B4P to PKN (MAX1665X)........................................-0.3V to +24V B3P to PKN (MAX1665V)........................................-0.3V to +18V B2P to PKN (MAX1665S)........................................-0.3V to +12V B1P to PKN, B2P to B1P, B3P to B2P, B4P to B3P...-0.3V to +6V CHG to PKN, DSG to BN MAX1665S............................................-0.3V to (VB2P + 0.3V) MAX1665V............................................-0.3V to (VB3P + 0.3V) MAX1665X............................................-0.3V to (VB4P + 0.3V) B2P to BN (MAX1665S)..........................................-0.3V to +12V B3P to BN (MAX1665V)..........................................-0.3V to +18V B4P to BN (MAX1665X)..........................................-0.3V to +24V Continuous Power Dissipation (TA= +70C) 8-Pin SO (derate 5.88mW/C above +70C)...............471mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Temperature Range...........................................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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
(VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER B2P Voltage Range B3P Voltage Range B4P Voltage Range Overvoltage Threshold Overvoltage Hysteresis Undervoltage Threshold Undervoltage RESET Overcurrent Sense Threshold Overcurrent Hysteresis Overvoltage/Undervoltage Delay Overcurrent Detection Delay CHG, DSG Output Voltage High DSG Output Voltage High (Note 2) CHG Output Voltage Low DSG Output Voltage Low CHG, DSG Output Source Current CHG Output Sink Current DSG Output Sink Current Overcurrent Sampling - tON Overcurrent Sampling - tOFF VCHGL VDSGL IOH IOL IOL tON tOFF SYMBOL VB2P VB3P VB4P VOV VCE VUV VRE VCH VCH2 tUV tIO MAX1665S IOUT = 100A MAX1665V MAX1665X MAX1665X, IOUT = 100A, VB4P = 24V, VBN = 100mV ICHG = -100A IDSG = -1A CHG = PKN, DSG = BN VCHG = VPKN + 3.0V VDSG = VBN + 3.0V VPKN = 300mV VPKN = 300mV MAX1665SESA, VB1P = 4V Input Bias Current (Note 3) IBIAS MAX1665VESA, VB1P = 4V, VB2P = 8V MAX1665XESA, VB1P = 4V, VB2P = 8V, VB3P = 12V 10 0.5 0.5 25 2 2 8.2 135 3 3 3 10 10 10 nA VB2P - 1.8 VB3P - 1.8 VB4P - 1.8 17 (Note 1) VBN - VPKN 2.4 0 200 MAX1665S MAX1665V MAX1665X Cell voltage rising CONDITIONS MIN 4 4 4 4.26 4.3 0.10 2.5 18 250 5 200 10 VB2P - 0.54 VB3P - 0.54 VB4P - 0.54 20 VPKN + 0.1 VBN + 0.1 V V V mA mA A ms ms nA V 2.6 30 300 TYP MAX 10 15 20 4.34 UNITS V V V V V V mV mV mV ms ms
2
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Lithium-Ion Battery Pack Protector
ELECTRICAL CHARACTERISTICS (continued)
(VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Input Bias Current Matching Supply Current Standby Mode Current Undervoltage Lockout SYMBOL IBIAS ICC ILP VUVLO (Note 5) DSG = CHG = low (Notes 3, 4) CONDITIONS MIN TYP 500 16 0.7 4.0 25 1 4.7 MAX UNITS pA A A V
MAX1665S/V/X
ELECTRICAL CHARACTERISTICS
(VB2P = 8V (MAX1665S), VB3P = 12V (MAX1665V), VB4P = 16V (MAX1665X), TA = -40C to +85C, unless otherwise noted.) (Note 6) PARAMETER B2P Voltage Range B3P Voltage Range B4P Voltage Range Overvoltage Threshold Undervoltage Threshold Undervoltage RESET Overcurrent Sense Threshold CHG, DSG Output Voltage High DSG Output Voltage High (Note 2) CHG Output Voltage Low DSG Output Voltage Low CHG, DSG Output Source Current CHG Output Sink Current DSG Output Sink Current VCHGL VDSGL IOH IOL IOL SYMBOL VB2P VB3P VB4P VOV VUV VRE VCH MAX1665S IOUT = 100A MAX1665V MAX1665X MAX1665X, IOUT = 100A, VB4P = 24V, VBN = 100mV ICHG = -100A IDSG = -1A CHG = PKN, DSG = BN VCHG = VPKN + 0.3V VDSG = VBN + 0.3V MAX1665SESA, VB1P = 4V Input Bias Current (Note 3) IBIAS MAX1665VESA, VB1P = 4V, VB2P = 8V MAX1665XESA, VB1P = 4V, VB2P = 8V, VB3P = 12V (Note 5) DSG = CHG = low 10 0.2 0.2 10 10 10 30 2 4.7 A A V nA VBN- VPKN MAX1665S MAX1665V MAX1665X Cell voltage rising CONDITIONS MIN 4 4 4 4.20 2.4 0 180 VB2P - 2 VB3P - 2 VB4P - 2 TYP MAX 10 15 20 4.24 2.6 30 320 VB2P - 0.5 VB3P - 0.5 VB4P - 0.5 20 VPKN + 0.1 VBN + 0.1 V V V mA mA A V UNITS V V V V V mV mV
Supply Current Standby Mode Current Undervoltage Lockout Note 1: Note 2: Note 3: Note 4: Note 5: Note 6:
ICC ILP VUVLO
Applies to the differential voltage measured on any cell. DSG is internally clamped to a maximum of 20V to protect the external MOSFET (VGS). Guaranteed by design. The input bias matching between cells is measured with a 4V voltage between cells. At least one cell is _______________________________________________________________________________________
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
OVERVOLTAGE THRESHOLD vs. TEMPERATURE
MAX1665 toc01
UNDERVOLTAGE THRESHOLD vs. TEMPERATURE
MAX1665 toc02
OVERCURRENT THRESHOLD vs. TEMPERATURE
MAX1665 toc03
4.34
2.51 UNDERVOLTAGE THRESHOLD (V)
255 OVERCURRENT THRESHOLD (mV)
THRESHOLD VOLTAGE (V)
4.30
2.50
252
4.26 HYSTERESIS 4.22
2.49
249
2.48
246
4.18 VBN - VPKN 4.14 -40 -15 10 35 60 85 TEMPERATURE (C)
2.47 VBN - VPKN 2.46 -40 -15 10 35 60 85 TEMPERATURE (C)
243 VBN - VPKN 240 -40 -15 10 35 60 85 TEMPERATURE (C)
OVERDISCHARGE THRESHOLD vs. TEMPERATURE
MAX1665 toc04
SUPPLY CURRENT vs. TEMPERATURE
MAX1665 toc05
OVERDISCHARGE THRESHOLD (mV)
-242 -244 -246 -248 -250 -252 -254 -256 -258 -260 -40 -15 10 35 60 VBN - VPKN
STANDBY CURRENT (A)
SUPPLY CURRENT (A)
17.5
0.9
0.8
17.0
0.7
16.5
0.6 16.0 85 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C)
0.5 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
QUIESCENT CURRENT vs. SUPPLY VOLTAGE
MAX1665 toc07
CONTINUOUS OVERCHARGE CONDITION
MAX1665 toc08
CONTINUOUS OVERDISCHARGE CONDITION
MAX1665 toc09
18.0
QUIESCENT CURRENT (A)
17.6
17.2
16.8 CHG 2V/div NORMALIZED TO ONE CELL 16.0 2.5 3.0 3.5 4.0 4.5 5.0 50ms/div 50ms/div SUPPLY VOLTAGE PER CELL (V) DSG 2V/div
16.4
4
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MAX1665 toc06
-240
STANDBY MODE CURRENT vs. TEMPERATURE
1.0
18.0
Lithium-Ion Battery Pack Protector
Pin Description
PIN NAME MAX1665S 1, 8 -- 2 3 4 5 6 7 -- MAX1665V 1 -- 2 3 4 5 6 7 8 MAX1665X -- 1 2 3 4 5 6 7 8 I.C. B4P DSG CHG PKN BN B1P B2P B3P Internally Connected. Make no connection to this pin. Cell 4 Positive Input. Connect to the positive terminal of the fourth series Li+ cell. Discharge Control Output. Drives the gate of an external N-channel MOSFET to control the discharge path. Charge Control Output. Drives the gate of an external N-channel MOSFET to control the charge path. Pack Negative Input Connect to the negative terminal of the first series Li+ cell. Cell 1 Positive Input. Connect to the positive terminal of the first series Li+ cell. Cell 2 Positive Input. Connect to the positive terminal of the second series Li+ cell. Cell 3 Positive Input. Connect to the positive terminal of the third series Li+ cell. FUNCTION
MAX1665S/V/X
Table 1. Functionality Truth Table for VBN < VPKN + 0.018V (Discharge Mode)
CHARGE OVERCURRENT 0 0 0 0 0 0 0 0 DISCHARGE OVERCURRENT 0 0 0 0 1 1 1 1 OVERVOLTAGE 0 0 1 1 0 0 1 1 UNDERVOLTAGE 0 1 0 1 0 1 0 1 CHG High Low Low Low Gated Low Low Low DSG High Low High Low Gated Low Gated Low GATE CLOCKED No No No No Yes No Yes No MAX SUPPLY CURRENT* (A) 25 1 25 1 25 1 25 1
*Assuming no load on CHG or DSG.
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
Table 2. Functionality Truth Table for VBN > VPKN + 0.018V (Charge Mode)
CHARGE OVERCURRENT 0 0 0 0 1 1 1 1 DISCHARGE OVERCURRENT 0 0 0 0 0 0 0 0 OVERVOLTAGE 0 0 1 1 0 0 1 1 UNDERVOLTAGE 0 1 0 1 0 1 0 1 CHG High High Low Low Gated Gated Low Low DSG High High High High Gated Gated High High GATE CLOCKED No No No No Yes Yes No No MAX SUPPLY CURRENT* (A) 25 25 25 25 25 25 25 25
*Assuming no load on CHG or DSG.
SUPPLIES RDY = 1 ON DSG = 0 CHG = 0 START START-UP T = COUNTER T = ZCHK DSG = 0 2.4ms DSG = 0 160s CHG = 0 CHG = 0 START-UP MEASURE DSG = 0 CHG = 0 WAIT FOR BLANK = 0 DSG = 0 CHG = 0
POWER ON
POWER ON
SLEEP CHARGE = 1 DSG = 0 CHG = 0
T = 640s
T = 2.4ms
CHARGE = 0
SHORT = 1
UV = 0 OV = 0
NORMAL DSG = 1 CHG = 1
T = 2.4ms
NORMAL PULSE OFF T = DSG = * 96ms CHG = *
NORMAL PULSE ON T = DSG = 1 6.4ms CHG = 1
NORMAL ZCHK DSG = 1 CHG = 1
T = 160s
NORMAL MEASURE DSG = 1 CHG = 1
T = 640s
SHORT = 1
UV = 0 OV = 1
OV DSG = 1 CHG = 0
T = 2.4ms
OV PULSE OFF T = 96ms DSG = 1 CHG = 0
OV PULSE ON T = DSG = 1 6.4ms CHG = 0
OV ZCHK DSG = 1 CHG = 0
T = 160s
OV MEASURE DSG = 1 CHG = 0
T = 640s
SHORT = 1
UV = 1 OV = 0
UV DSG = 1 CHG = 1
T = 2.4ms
UV PULSE OFF T = DSG = * 96ms CHG = *
CHARGE = 0
UV PULSE ON T = DSG = 1 6.4ms CHG = 1
CHARGE = 0
UV ZCHK DSG = 1 CHG = 1
T = 160s
UV MEASURE DSG = 1 CHG = 1
T = 640s
CHARGE = 0
CHARGE = 0 SHORT = 1
UV = 1 OV = 1
OV & UV DSG = 1 CHG = 0
T = 2.4ms
OV & UV PULSE OFF T = DSG = 1 96ms CHG = 0
OV & UV PULSE ON T = DSG = 1 6.4ms CHG = 0
OV & UV ZCHK DSG = 1 CHG = 0
T = 160s
OV & UV MEASURE DSG = 1 CHG = 0
T = 640s
* = 0 FOR OVERCURRENT FAULT; 1 OTHERWISE
Figure 1. State Diagram
_______________Detailed Description
The MAX1665S, MAX1665V, and MAX1665X supervise the charging and discharging processes on Li+ cells. Designed for 2, 3, and 4-cell applications, these devices monitor the voltage across each cell to provide protection against overcurrent, overvoltage, and undervoltage.
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Figure 1 shows the MAX1665 state diagram. Two control pins, CHG and DSG, drive the gates of two seriesconnected external N-channel MOSFETs, enabling/ disabling the charging/discharging process as necessary (see Typical Operating Circuit). The voltages at B1P, B2P, B3P, and B4P are measured differentially
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
across each cell to determine if the voltage levels are within operating range. As depicted in the typical operating circuit, when CHG and DSG are high, the MOSFETs are on, allowing the cells to charge or discharge. However, when the charge or discharge current becomes excessive, the device turns off the FETs, enters a standby mode, and periodically samples the current to determine if the fault condition is removed. The MAX1665 does not sample the current directly, but rather measures the differential voltage across BN and PKN produced by the charge or discharge current flowing through the drain-to-source resistance of the MOSFETs. A preset voltage threshold is used to prevent excess current flow (see Electrical Characteristics). In operating mode, all of the MAX1665 versions consume less than 25A of quiescent current, allowing long-term battery storage without significantly affecting battery life. In standby mode, these devices consume less than 1A of quiescent current.
Overcurrent Protection
When the MAX1665 detects overcurrent in the system, it disables the charge or discharge process by connecting CHG to PKN and DSG to BN, turning off the external MOSFETs (see Typical Operating Circuit). In charge mode, the MAX1665 detects overcharge when the voltage from BN to PKN exceeds +250mV. In discharge mode, overdischarge occurs when the differential voltage is less than -250mV. During any overcurrent condition, CHG and DSG are gated at 12Hz until the overcurrent is removed. If both an overvoltage and overcharge condition exist, the overvoltage condition takes priority. Likewise, if undervoltage and overdischarge conditions exist, the overdischarge condition takes priority. For more details, see Tables 1 and 2.
Cell Current Balancing
When the battery cells are matched, the MAX1665 draws zero current from the intermediate nodes. The MAX1665 draws current from the top terminal only. Figure 2 shows a simplified diagram of the voltage sampling scheme. The following equations show that, for balanced cells, the differential discharge currents are zero: B4P: I4 = 3ICB + V4 / R = 4V4 / R = BAT4 current B3P: I3 = I3P + I4 = BAT3 current I3P + ICB = V3 / R I3P = V3 / R - V4 / R I3 = I4 + (V3 - V4) / R = (3V4 + V3) / R B2P: I2 = I2P + I3 = BAT2 current I2P + ICB = V2 / R I2P = V2 / R - V4 / R I2 = I3 + V2 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R = (2V4 + V3 + V2) / R B1P: I1 = I1P + I2 = BAT1 current I1P + ICB = V1 / R I1P = V1 / R - V4 / R I1 = I2 + V1 / R - V4 / R = I4 + (V3 - V4) / R + (V2 - V4) / R + (V1 - V4) / R = (V4 + V3 + V2 + V1) / R when V1 = V2 = V3 = V4, I1P = I2P = I3P = 0 and I1 = I2 = I3 = I4 = 4V4 / R. Due to process variations, the MAX1665 does draw a minute current (70nA ~ 150nA) from the intermediate node even when the cells are matched. This current difference exists in the sampling mode, which is 1/32 of the whole time period, making the average of this current 2nA to 5nA.
Overvoltage Protection
When any individual cell voltage rises above VOV (overvoltage limit), the charge MOSFET control pin (CHG) is driven to PKN, thereby disconnecting the charger from the cells. The MAX1665 measures each cell of the pack differentially to prevent overcharging on a cell-by-cell basis. The charging process resumes when the highest cell voltage drops below VOV - 100mV (see Typical Operating Circuit).
Undervoltage/Overdischarge Protection
Discharge can occur whenever the voltage of each cell is above the undervoltage threshold voltage (VUV, typically 2.50V). If the voltage on any of the cells falls below VUV, CHG latches to PKN and DSG latches to BN. Quiescent current falls to under 1A as the device enters the standby mode. The latch resets when BN exceeds PKN by 18mV. During charge mode, when BN is greater than PKN, the latch is held in reset, which disables the undervoltage comparator feature and allows charging on the cells. During the initialization process, as cells are connected to the MAX1665, the device considers this a low-voltage condition and disables CHG and DSG until a charging source is applied to create at least an 18mV differential between BN and PKN. During long-term storage, the battery will self-discharge until it reaches the undervoltage threshold. When this happens, the MAX1665 enters standby mode. Normal operating mode resumes when a charger is connected, causing BN to rise 18mV above PKN.
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
BP4 + V4 + V3 I4 BP3 I3 I3P ICB V4 R BP2 + V2 I2 I2P ICB V4 R+ V2 B1P1 I1P + V1 R R + V3 R + V4 R B2P1 ICB V4 R B3P1
Table 3. Recommended MOSFETs
DUAL N-CHANNEL MOSFETs IRF9956 FDS6990A Si9936 TYPICAL RDS(ON) () 0.10 0.018 0.050 MAX VGS (V) 20 20 20
BP1 I1
+ V1
1 V1 R V2 R V3 R V4 R PACK+ CELL 2 8 7
I.C. I.C. B2P
Figure 2. Sampling Mode Equivalent Circuit
CELL 1
6 5 IRF7101
B1P BN
Applications Information
Choosing an External MOSFET
The external N-channel MOSFETs act as gated switches to enable or disable the charging/discharging process. CHG and DSG control the gate of these external MOSFETs to prevent damage to the Li+ cells. For overcurrent conditions, the voltage at DSG equals the voltage at BN, thereby reducing all current flow, including the path through the body diode of the N-channel MOSFET. Note that the MAX1665X clamps the VGS voltage to a maximum of 20V. The IRF7101 is a low-cost, dual N-channel MOSFET that is available in a small 8-pin SO package. Depending on the maximum charge and discharge rates, use different MOSFETs to optimize each application. Table 3 summarizes recommended MOSFETs.
OVERDISCHARGE PROTECTION
MAX1665S
2
DSG
IRF7101 OVERCHARGE PROTECTION 3 CHG
PACK-
4
PKN
Figure 3. Typical 2-Cell Operating Circuit
2, 3, and 4-Cell Applications
Figures 3 through 5 depict circuits for 2, 3, and 4-cell applications. Note that the two series MOSFETs (IRF7101 dual N-channel MOSFETs) are oriented to prevent body diode current flow. The indicated polarity symbols show the connection for the external source required to charge the Li+ cells. This external charger source also supplies the gate drive to the MOSFETs through pack + voltage / pack.
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
1 PACK+ CELL 3 CELL 2 CELL 1 8 7
I.C. B3P
PACK+ CELL 4 CELL 3
1 8 7 6 5 IRF7101
B4P B3P B2P B1P BN
B2P CELL 2
6 5 IRF7101
B1P CELL 1 BN
MAX1665V
MAX1665X
OVERDISCHARGE PROTECTION
2
DSG
OVERDISCHARGE PROTECTION
2
DSG
IRF7101 OVERCHARGE PROTECTION 3 CHG OVERCHARGE PROTECTION
IRF7101 3 CHG
PACK-
4
PKN
PACK-
4
PKN
Figure 4. Typical 3-Cell Operating Circuit
Figure 5. Typical 4-Cell Operating Circuit
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
________________________________________________________Package Information
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
NOTES
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Lithium-Ion Battery Pack Protector MAX1665S/V/X
NOTES
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 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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