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19-3495; Rev 0; 11/04
High-Voltage, Low-Power Linear Regulators for Notebook Computers
General Description
The MAX8718/MAX8719 are micropower, 8-pin TDFN linear regulators that supply always-on, keep-alive power to CMOS RAM, real-time clocks (RTC), and microcontrollers in systems with high-voltage batteries. The circuits consist of a 100mA linear regulator and a power-good comparator (PGOOD) with fixed-output delay. Key features include wide input voltage range, low-dropout voltage, and low-quiescent supply current. Despite a miserly 25A (max) no-load quiescent current, the MAX8718/MAX8719 have good line- and loadtransient response and excellent AC power-supply rejection. They provide a clean fixed 5V or 3.3V output (MAX8718), or an adjustable 1.24V to 28V output (MAX8719), even when subjected to fast supply-voltage changes that occur during the switchover from battery to AC-adapter input power. The space-saving TDFN package has excellent thermal characteristics and tolerates up to 1951mW of power dissipation. Internal foldback current limiting and thermal shutdown protect the regulator from overload and thermal faults. In addition to the main notebook-computer application, these devices are useful in other low-power, high-voltage applications (4V < VIN < 28V) such as smart batteries, current control loops, telecom emergency power, and housekeeping power for off-line supplies. The MAX8718/MAX8719 are available in a thermally enhanced 3mm x 3mm, 8-lead TDFN package. 4V to 28V Input Range 18A Quiescent Supply Current <3A Shutdown Supply Current 100mA Output Current 3.3V or 5V, Pin-Selectable Output (MAX8718) Adjustable 1.24V to 28V Output (MAX8719) 2% Output Accuracy Thermal-Overload Protection Delayed Power-Good Output Thermally Enhanced 8-Pin TDFN Package
Features
MAX8718/MAX8719
Ordering Information
PART TEMP RANGE PIN-PACKAGE 8 TDFN 3mm x 3mm 8 TDFN 3mm x 3mm OUTPUT VOLTAGE 3.3V/5V Adjustable
MAX8718ETA -40C to +85C MAX8719ETA -40C to +85C
Applications
CMOS/RTC Backup Power Microcontroller Power Notebook Computers Smart-Battery Packs PDAs and Handy-Terminals Battery-Powered Systems
IN 1 GND 2 5/3 (FB) 3 VCC 4
Pin Configuration
TOP VIEW
8 OUT
MAX8718 MAX8719
7 I.C. 6 SHDN 5 PGOOD
TDFN 3mm x 3mm
() ARE FOR THE MAX8719.
________________________________________________________________ Maxim Integrated Products
1
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +30V SHDN to GND ..............................................-0.3V to (VIN + 0.3V) 5/3 (MAX8718) to GND.............................................-0.3V to +6V FB (MAX8719) to GND .............................................-0.3V to +6V OUT (MAX8718) to GND ..........................................-0.3V to +6V OUT (MAX8719) to GND ........................................-0.3V to +30V VCC to GND (MAX8718) ...........................................-0.3V to +6V VCC to GND (MAX8719) ........................................-0.3V to +2.7V PGOOD to GND .....................................................-0.3V to +30V I.C. to GND ...............................................................-0.3V to +6V OUT Short Circuit to GND.......................................................30s Continuous Power Dissipation (TA = +70C) 8-Pin TDFN (derate 24.4mW/C above +70C) ..........1951mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage 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
(Circuit of Figure 1. VIN = 15V, IOUT = 5A, TA = 0C to +85C. Typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Input Voltage Range Supply Current (MAX8718) VCC Input Current (MAX8719) VCC Input Current (MAX8718) OUT Minimum Load Current Shutdown Supply Current Dropout Supply Current SHDN = 0V VOUT set to 5V, VIN = 4.7V VIN = 6V to 28V, ILOAD = 1mA, 5/3 = GND, TA = +25C VIN = 6V to 28V, ILOAD = 1mA, 5/3 = OUT, TA = +25C VIN = 6V to 28V, ILOAD = 5A to 100mA, 5/3 = GND VIN = 6V to 28V, ILOAD = 5A to 100mA, 5/3 = OUT FB = OUT, VIN = 6V to 28V, ILOAD = 1mA FB Threshold (MAX8719) VFB FB = OUT, VIN = 6V to 28V, ILOAD = 5A to 100mA (Note 2) VFB = 1.3V, TA = +25C VFB = 1.3V, TA = 0C to +85C V5/3 = 5V, TA = +25C V5/3 = 5V, TA = 0C to +85C -30 2 560 3.26 4.95 3.15 4.75 1.215 1.18 -30 15 +30 1.240 1.2 85 3.33 5.05 3.40 5.15 V 3.48 5.25 1.265 1.28 +30 V SYMBOL VIN IIN SHDN = IN, TA = +25C SHDN = IN, VIN = 6V to 28V 0V < VCC < 2.7V, TA = +25C 0V < VCC < 2.7V, TA = 0C to +85C 0V < VCC < 5.5V, TA = +25C 0V < VCC < 5.5V, TA = 0C to +85C 2.3 5 3 -0.1 0.04 3.4 CONDITIONS MIN 4 12 TYP MAX 28 18 25 +0.1 UNITS V s A A A A A A
OUT Output Voltage (MAX8718)
FB Input Current (MAX8719) 5/3 Input Current (MAX8718) Dropout Voltage
IFB I5/3
nA nA mV
VDROPOUT ILOAD = 100mA (Note 3)
2
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High-Voltage, Low-Power Linear Regulators for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VIN = 15V, IOUT = 5A, TA = 0C to +85C. Typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Output Current Limit Output Reverse Leakage Current Capacitive Load Requirements SYMBOL ILIM CONDITIONS VIN = 6V, TA = +25C VOUT = 0, VIN = 6V VOUT forced to 5.5V, IN = unconnected MAX8718 MAX8719 Rising edge of IN or SHDN to OUT within spec limits, COUT = 10F, RLOAD = 500, VOUT = 5V COUT = 10F, RLOAD = 500, OUT within 90% of the nominal output voltage TA = +25C, rising edge only VCC Threshold (MAX8718) 0C < TA < +85C, rising edge only TA = +25C, rising edge only VCC Threshold (MAX8719) 0C < TA < +85C, rising edge only VCC to PGOOD Delay PGOOD Active-Timeout Period PGOOD Output Leakage Current PGOOD Output Low Voltage VCC Input Hysteresis Thermal-Shutdown Threshold SHDN Input Low Voltage SHDN Input High Voltage SHDN Input Bias Current V SHDN = 0 or 15V, TA = 0C to +85C 1.4 -1 +0.1 +1 V SHDN = 0 or 15V, 20C hysteresis PGOOD = 5.5V, VCC = 5.5V ISINK = 1.6mA, VCC = GND 2 +165 0.25 VTH to (VTH - 100mV) 100 0.88 x VOUT 0.85 x VOUT 0.88 x VFB 0.85 x VFB 0.5 0.9 x VOUT 0.9 x VOUT 0.9 x VFB 0.9 x VFB 4.5 185 300 0.1 0.3 0.92 x VOUT 0.95 x VOUT 0.92 x VFB 0.95 x VFB 0.16 0.23 1 125 70 MIN TYP 210 340 MAX UNITS mA A F/mA
MAX8718/MAX8719
Startup Time Response
ms
Startup Output Overshoot
%
V
V
s ms A V % C V V A
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1 VIN = 15V, IOUT = 5A, TA = -40C to +85C, unless otherwise noted.) (Note 4)
PARAMETER Input Voltage Range Supply Current (MAX8718) Supply Current (MAX8719) OUT Minimum Load Current Shutdown Supply Current SHDN = 0V VIN = 6V to 28V, ILOAD = 5A to 100mA, 5/3 = GND OUT Output Voltage (MAX8718) VIN = 6V to 28V, ILOAD = 5A to 100mA, 5/3 = OUT FB = OUT, VIN = 6V to 28V, ILOAD = 1mA FB Threshold (MAX8719) FB Input Current (MAX8719) 5/3 Input Current (MAX8718) Dropout Voltage Output Current Limit Capacitive Load Requirements VFB IFB I5/3 ILIM FB = OUT, VIN = 6V to 28V, ILOAD = 5A to 100mA (Note 2) VFB = 1.3V V5/3 = 5V VOUT = 0, VIN = 6V MAX8718 MAX8719 Rising edge of IN or SHDN to OUT within spec limits, COUT = 10F, RLOAD = 500, VOUT = 5V -40C < TA < +85C, rising edge only -40C < TA < +85C, rising edge only 0.85 x VOUT 0.85 x VFB 100 ISINK = 1.6mA, VCC = GND 1.4 V SHDN = 0 or 15V, TA = -40C to +85C -1 +1 4.72 1.215 1.18 -40 -30 125 0.16 0.23 1 0.95 x VOUT 0.95 x VFB 300 0.3 0.25 5.25 1.265 1.28 +40 +30 560 375 V nA nA mV mA F/mA 3.10 SYMBOL VIN IIN IIN SHDN = IN, VIN = 6V to 28V SHDN = IN, VIN = 6V to 28V CONDITIONS MIN 4 TYP MAX 28 25 25 5 3 3.48 V UNITS V A A A A
VDROPOUT ILOAD = 100mA (Note 3)
Startup Time Response
ms
VCC Threshold (MAX8718) VCC Threshold (MAX8719) PGOOD Active-Timeout Period PGOOD Output Low Voltage SHDN Input Low Voltage SHDN Input High Voltage SHDN Input Bias Current
V V ms V V V A
Note 1: Limits are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed through correlation using standard quality control (SQC) methods. Note 2: Pulse test at VIN = 28V, IOUT = 100mA to avoid exceeding package power-dissipation limits. Note 3: Dropout voltage is tested by reducing the input voltage until VOUT drops to 100mV below its nominal value as measured with VIN starting 2V above VOUT. Note 4: Specifications to -40C are guaranteed by design, not production tested.
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
Typical Operating Characteristics
(Circuit of Figure 1. VIN = 15V, VOUT = 3.3V, TA = +25C, unless otherwise noted.)
SAFE LOAD-CURRENT OPERATING AREA vs. SUPPLY VOLTAGE
MAX8718/19 toc01
GROUND CURRENT vs. SUPPLY VOLTAGE AT VARIOUS LOADS
MAX8718/19 toc02
SUPPLY CURRENT vs. SUPPLY VOLTAGE
18.5 SUPPLY CURRENT (A) 18.0 17.5 17.0 16.5 16.0 15.5 TA = -40C TA = +25C TA = +85C
MAX8718/9 toc03
120.0 100.0 LOAD CURRENT (mA) 80.0 60.0 40.0 20.0 0 0 5 10 15 20 25 POWER-DISSIPATION LIMIT REGION
15.0 150mA GROUND CURRENT (mA) 12.0 110mA 9.0 70mA 6.0 30mA 3.0 10mA
19.0
0 30 5 10 15 20 25 30 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V)
15.0 5 10 15 20 25 30 SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX8718/19 toc04
SUPPLY CURRENT vs. TEMPERATURE
MAX8718/9 toc05
RIPPLE REJECTION vs. FREQUENCY
-70 RIPPLE REJECTION (dB) -60 -50 -40 -30 -20 -10 10mA LOAD CURRENT 0
MAX8718/19 toc06
1.6 SHUTDOWN SUPPLY CURRENT (A) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 TA = +25C 0 2 6 10 14 18 22 26
19.0 18.5 SUPPLY CURRENT (A) 18.0 17.5 17.0 16.5 16.0 15.5 15.0
VIN = 15V
-80
30
-40
-20
0
20
40
60
80
100
0.01
0.1
1 FREQUENCY (kHz)
10
100
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
LOAD-TRANSIENT RESPONSE
MAX8718/9 toc07
LINE-TRANSIENT RESPONSE
MAX8718/9 toc08
VOUT 100mV/div
VOUT 200mV/div AC-COUPLED +20V VIN
IOUT 100mA/div CIN = 10F, COUT = 10F 200s/div 100s/div
+10V
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 15V, VOUT = 3.3V, TA = +25C, unless otherwise noted.)
DROPOUT SUPPLY CURRENT vs. SUPPLY VOLTAGE
140 120 TA = +25C 100 80 60 40 20 0 100s/div 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 SUPPLY VOLTAGE (V) TA = -40C
MAX8718/19 toc10 MAX8718/9 toc12 MAX8718/9 toc11
TIME TO EXIT SHUTDOWN
MAX8718/9 toc09
160 +5V DROPOUT SUPPLY CURRENT (A) TA = +85C
VOUT 0V
SHDN 5V/div VIN = 15V
DROPOUT VOLTAGE vs. LOAD CURRENT
350 300 DROPOUT VOLTAGE (mV) 250 200
PGOOD TRANSIENT RESPONSE
+5V VCC 0V
150 100 50 0 0 10 20 30 40 50 60 70 80 90 100 LOAD CURRENT (mA) 40ms/div +5V PGOOD 0V
PGOOD ACTIVE-TIMEOUT PERIOD vs. TEMPERATURE
PGOOD ACTIVE-TIMEOUT PERIOD (ms)
MAX8718/9 toc13
180 175 170 165 160 155 150 -40 -20 0 20 40 60 TEMPERATURE (C) 80
100
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High-Voltage, Low-Power Linear Regulators for Notebook Computers
Pin Description
PIN MAX8718 1 2 3 -- 4 5 6 7 8 MAX8719 1 2 -- 3 4 5 6 7 8 NAME IN GND 5/3 FB VCC PGOOD SHDN I.C. OUT FUNCTION Positive Supply Input. Connect to a +4V to +28V supply. Ground Preset Output-Voltage Select Input. Connect 5/3 to GND for 3.3V output, or to OUT for 5V output. Feedback Input. Regulates to 1.24V nominally. PGOOD Sense Input Power-Good Output Shutdown Control Input Internal Connection. This pin is internally connected for test purposes; leave it unconnected in the application. 100mA Regulator Output
MAX8718/MAX8719
IN 6V TO 28V 1F SHDN
OUT VCC 100k
OUTPUT 3.3V 10F 6V TO 28V 1F
IN SHDN
OUT VCC 100k
OUTPUT 10F
MAX8718
I.C. PGOOD 5/3 GND PGOOD I.C.
MAX8719
PGOOD R1 FB GND R2 PGOOD
Figure 1. Typical Operating Circuit of the MAX8718
Figure 2. Typical Operating Circuit of the MAX8719
Detailed Description
The MAX8718/MAX8719 low-quiescent-current linear regulators are designed primarily for high-input-voltage applications. The MAX8718 supplies a preselected 3.3V or 5.0V output for loads up to 100mA (Figure 1). The MAX8719 provides an adjustable voltage from 1.24V to 28V (Figure 2). The maximum output current is a function of the package's maximum power dissipation for a given temperature. A 5A load is required to maintain output regulation. The MAX8718's output voltage is fed back through an internal resistive voltage-divider connected to OUT. Set the output voltage to either 5.0V or 3.3V with the 5/3
pin. Select the 5V output by connecting 5/3 to OUT, or the 3.3V output by connecting 5/3 to GND. The MAX8719's output is adjustable with an external resistive voltage-divider. The typical feedback threshold is 1.24V (see the Setting the MAX8719 Output Voltage section). See Figure 3 for the MAX8718/ MAX8719 Functional Diagram.
Shutdown
The device enters shutdown mode when SHDN is low. In shutdown mode, the internal pnp power transistor, control circuit, reference, and all biases turn off, reducing the supply current to below 3A. Connect SHDN to IN for automatic startup.
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
IN
MAX8718 MAX8719 REF
SHDN
BIAS
OUT
THERMAL SHUTDOWN
CURRENT LIMIT
FB (MAX8719)
5/3 (MAX8718)
GND
PGOOD VCC DELAY THRESHOLD
Figure 3. MAX8718/MAX8719 Functional Diagram
Current Limit
Output current is limited to 210mA (typ). The current limit exceeds the 100mA (min) safe operating limit. The output can be shorted to ground for 30 seconds without damaging the part.
sistor on again after the IC's junction temperature cools by 20C (typ), causing the output to pulse on and off during continuous thermal-overload conditions.
Operating Region and Power Dissipation
Maximum power dissipation depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of airflow. The device's power dissipation is P = IOUT x (VIN - VOUT). The power dissipation at +70C ambient is 1951mW (see the Absolute Maximum
Thermal-Overload Protection
When the junction temperature exceeds TJ = +165C, an internal thermal sensor sends a signal to the shutdown logic, turning off the pass transistor and allowing the IC to cool. The thermal sensor turns the pass tran8
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High-Voltage, Low-Power Linear Regulators for Notebook Computers
GND CIN 1 VIN 2 3 4 8 COUT
most applications. In applications that include analogto-digital converters (ADCs) of more than 12 bits, consider the ADC's power-supply rejection specifications.
MAX8718/MAX8719
Transient Response
The Typical Operating Characteristics show the MAX8718/MAX8719s' load-transient response. When a step-in load current is applied, there are two components to the regulator's response. There is an instantaneous step in the output voltage due to the output capacitor's ESR and the regulator's finite output impedance. The second, slower component is the regulator's active correction to the output voltage. Typical step changes in the OUT load current from 10mA to 20mA produce 20mV transients.
MAX8718 MAX8719
7 6 5
VOUT
Figure 4. Layout of High-Current Paths
Ratings). The thermal resistance junction-to-case of the TDFN package is 41C/W, and the maximum safe junction temperature is +150C. The GND pin and backside pad performs the dual function of providing an electrical connection to ground and channeling heat away from the package. Connect GND and the backside pad to ground using a metal trace or ground plane. The package's overall thermal resistance varies inversely with the copper PC board area attached to the part. To achieve rated thermal resistance, a copper region of at least 650mm2 should be attached to the MAX8718/MAX8719s' case.
Power-Good Output (PGOOD)
The MAX8718/MAX8719 include an independent power-good monitor. This circuit has an uncommitted sense input (VCC) that can be connected to the regulator's output or similar voltage. In the MAX8718, the comparator threshold tracks the output set point according to the state of 5/3. In the MAX8719, the comparator threshold is set to the feedback reference voltage. The PGOOD output goes high when V CC is greater than -10% of the regulation set point. There is a fixed 100ms (min) delay when the output goes into regulation, which helps ensure proper output-voltage settling. The PGOOD delay when transitioning out of regulation is much faster, 4.5s (typ), which permits the system to respond as fast as possible to the out-of-regulation condition. The power-good monitor has an open-drain output, which can be externally pulled up to OUT. The voltage rating for PGOOD is 28V.
Applications Information
Setting the MAX8719's Output Voltage
Set the MAX8719's output voltage with a resistive voltage-divider (R1 and R2 in Figure 3). Choose R2 = 125k or less to maintain a 10A minimum load on OUT. Calculate R1 using the following equation: V R1 = R2 x OUT - 1 VFB where VFB = 1.24V (typ).
Layout Guidelines
Good layout is important to minimize the effects of noise and ensure accurate voltage regulation. Use appropriate trace widths for the high-current paths and keep traces short to minimize parasitic inductance and capacitance. Figure 4 shows a layout of the high-current paths. Place bypass capacitors close to the IN and OUT pins. When using the MAX8719, the feedback resistors should be placed close to the device to avoid voltage drops on ground that may shift the output voltage. Connect the exposed backside paddle to as large a copper area as practical.
Capacitor Selection
Use a 0.1F (min) capacitor on the input. Higher values improve the line-transient response. Use a 1F (min) capacitor on the output, or a 15F capacitor for the full 100mA load current. Otherwise, use a 1F plus 0.16F/mA (0.23F/mA for the MAX8719). For output voltages less than 3.3V, use 15F instead of 10F. The output capacitor's equivalent series resistance (ESR) must be less than 1 for stable operation.
Chip Information
TRANSISTOR COUNT: 1298 PROCESS: BiCMOS
Output-Voltage Noise
The MAX8718/MAX8719 typically exhibit 5mV P-P of noise during normal operation. This is negligible in
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High-Voltage, Low-Power Linear Regulators for Notebook Computers MAX8718/MAX8719
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
6, 8, &10L, DFN THIN.EPS
C L
D
N
PIN 1 INDEX AREA
E
DETAIL A
E2
C L
L A e e
L
PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY
21-0137
F
1
2
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 MAX. 0.80 3.10 3.10 0.05
0.40 0.20 0.25 MIN. 0.20 REF.
PACKAGE VARIATIONS PKG. CODE T633-1 T833-1 T1033-1 T1433-1 T1433-2 N 6 8 10 14 14 D2 1.500.10 1.500.10 1.500.10 1.700.10 1.700.10 E2 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.65 BSC 0.50 BSC 0.40 BSC 0.40 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEC MO229 / WEED-3 ------b 0.400.05 0.300.05 0.250.05 0.200.03 0.200.03 [(N/2)-1] x e 1.90 REF 1.95 REF 2.00 REF 2.40 REF 2.40 REF
PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
21-0137
F
2
2
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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