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19-3568; Rev 0; 3/05
Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers
General Description
The MAX1350-MAX1357 offer two programmable highside current-sense amplifiers and two drive amplifiers integrated in a single package. The current-sense amplifiers have a 5V to 32V commonmode input range and provide a voltage output that is a multiple of the sense voltage. The common-mode input range is independent of supply voltage. An external sense resistor determines the range of current monitored by a current-sense amplifier. Gains of 2 or 10 are available with a typical input-referred offset voltage of zero or 3mV. The 3mV offset option is ideal for applications where offset nulling is required. The drive amplifiers provide up to 10mA of output current capability and a high output capacitive load tolerance. Output transients are limited to 100mV during power-up and power-down events. The drive amplifiers feature a digitally controllable fast output clamp to ground. The drive amplifier outputs are current limited and are offered with gains of 2 or 4. The drive amplifiers draw approximately 4.75mA, while the current-sense amplifiers draw approximately 250A with full-scale sense inputs. In shutdown mode, the total supply current reduces to less than 1A. The MAX1350-MAX1357 are available in a 20-pin TSSOP package and operate over the extended (-40C to +85C) temperature range.
Features
High-Side Current-Sense Amplifier with Gain of 2 or 10 1% Current-Sense Accuracy Wide 5V to 32V Common-Mode Voltage Range-- Independent of Supply Voltage Adjustable Low Noise 0 to 5V or 0 to 10V Output Voltage Ranges with 10mA Gate Drive Drive Amplifier Features Fast Clamp to Ground
MAX1350-MAX1357
Ordering Information
PART MAX1350EUP* MAX1351EUP* MAX1352EUP* MAX1353EUP* MAX1354EUP MAX1355EUP* MAX1356EUP* MAX1357EUP* TEMP RANGE** -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP
Applications
Cellular Base Stations Industrial Process Control Power Amplifiers
*Future product--contact factory for availability. **For parts that operate over a wider temperature range, contact factory for availability. Selector Guide appears at end of data sheet.
Pin Configurations
TOP VIEW
N.C. 1 CAL1 2 SHDN 3 OUTCS1 4 IN1 5 IN2 6 OUTCS2 7 CAL2 8 CSGND 9 DRGND 10
20 CLAMP1 19 CS1+ 18 CS117 OUT1
N.C. 1 N.C. 2 SHDN 3 OUTCS1 4 IN1 5 IN2 6 OUTCS2 7 N.C. 8 CSGND 9 DRGND 10
20 CLAMP1 19 CS1+ 18 CS117 OUT1
MAX1350 MAX1351 MAX1356 MAX1357
16 OUT2 15 CS214 CS2+ 13 CLAMP2 12 VDD 11 VSS
MAX1352- MAX1355
16 OUT2 15 CS214 CS2+ 13 CLAMP2 12 VDD 11 VSS
TSSOP
TSSOP
________________________________________________________________ Maxim Integrated Products
1
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
ABSOLUTE MAXIMUM RATINGS
VDD to VSS ..............................................................-0.3V to +14V VSS to CSGND or DRGND....................................... -1V to +0.3V CSGND to DRGND............................................... -0.3V to +0.3V CS1+, CS2+ to VSS ...............................................-0.3V to +34V CS1- to CS1+ .......................................................... -6V to +0.3V or if CS1+ < 5.7V ...................................(-CS1 - 0.3)V to +0.3V CS2- to CS2+ .......................................................... -6V to +0.3V or if CS2+ < 5.7V ...................................(-CS2 - 0.3)V to +0.3V OUT1, OUT2 to VSS ......................................-0.3 to (VDD + 0.3V) CAL1, CAL2, SHDN to CSGND or DRGND..............-0.3V to +6V CLAMP1, CLAMP2 to CSGND or DRGND ...............-0.3V to +6V OUTCS1, OUTCS2 to VSS ......................................-0.3V to +34V IN1, IN2 to VSS ..............................................-0.3 to (VDD + 0.3V) Continuous Power Dissipation (TA = +70C) 20-Pin TSSOP (derate 11mW/C above +70C) .......879.1mW Operating Temperature Range ...........................-40C to +85C 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
(VDD = +10V, VSS = 0V, VCS_+ = 30V, COUTCS1, COUTCS2 to CSGND = 10pF, COUT1, COUT2 to DRGND = 10nF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Operating and Common-Mode Input Voltage Range Common-Mode Rejection Ratio Current-Sense Negative Input Bias Current Input-Referred Offset Voltage Input-Referred Offset Drift Full-Scale Sense Voltage Range (Note 2) Total Output Voltage Error (Note 3) Output Impedance ROUTCS_ VSENSE MAX1350-MAX1353 MAX1354-MAX1357 VSENSE = 100mV to 1250mV VSENSE = 20mV to 100mV VSENSE = 2mV to 20mV Measured at DC MAX1350/MAX1351 Output Voltage Range (Note 4) VOUTCS_ MAX1352/MAX1353 MAX1354/MAX1355 MAX1356/MAX1357 Voltage Gain Error -3dB Bandwidth Output Settling Time to 0.1% of Final Value Output Capacitive Load Input Referred Noise at 1kHz Power-Supply Rejection Ratio PSRR 5V < VCS_+ < 32V, measured at DC (Note 5) BW 2 2 -1.0 -5 -50 8.75 0.010 0.004 0.02 0.05 0.1 1.15 10 10 25 110 0.3 1.3 13 12.5 SYMBOL CONDITIONS MIN TYP MAX UNITS
HIGH-SIDE CURRENT-SENSE AMPLIFIER VCS_+ CMRR ICSMAX1352-MAX1355, TA = +25C VOS MAX1350/MAX1351/MAX1356/MAX1357, TA = +25C (Note 1) 5V < VCS_+ < 32V, measured at DC -1 -0.7 2.0 5 110 0.1 0.2 3.0 2 1250 500 +1.0 +5 +50 17.25 2.506 2.500 5.00 5.03 % MHz s pF nV/Hz dB V k % +1 +0.7 4.0 mV V/C mV 32 V dB A
2
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +10V, VSS = 0V, VCS_+ = 30V, COUTCS1, COUTCS2 to CSGND = 10pF, COUT1, COUT2 to DRGND = 10nF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Power-Up Time to 0.1% of Final Value Saturation Recovery Time Shutdown Recovery Time DRIVE AMPLIFIER Output Voltage Range for Full Accuracy Drive Amplifier Input Bias Current Output Impedance Settling Time to 0.1% of Final Value Output Capacitive Load Input-Referred Noise at 1kHz Voltage Gain Error -3dB Bandwidth Input-Referred Offset Voltage Input-Referred Offset Drift Common-Mode Rejection Ratio Power-Supply Rejection Ratio Clamp to Zero Delay Clamp to Zero Switch Impedance Output Short-Circuit Current Power-Up Time to 0.1% of Final Value Saturation Recovery Time Shutdown Recovery Time Maximum Power-On Transient DIGITAL INPUTS (SHDN, CLAMP1, CLAMP2, CAL1, CAL2) Input High Voltage Input Low Voltage Input Hysteresis Input Bias Current Input Capacitance POWER SUPPLIES Drive Supply Voltage Drive Supply Current Sense Supply Voltage Range VDD IDD VCS+ VSS = DRGND (Note 7) 5 4.75 4.75 11.00 7 32 V mA V -1.0 VIH VIL 0 0.1 5.0 +1.0 2.4 0.4 V V mV A pF RCLAMP ISC 1s, sinking or sourcing CMRR PSRR Measured at DC (Note 6) Measured at DC (Note 6) CLAMP_ driven high BW VOS MAX1350/MAX1352/MAX1354/MAX1356 MAX1351/MAX1353/MAX1355/MAX1357 -0.75 -0.20 COUT_ IIN_ ROUT_ At OUT_, IOUT_ = 10mA At OUT_, IOUT_ = 0.1mA (Note 6) Measured at DC RS = 50, COUT_ = 15F RS = 0, COUT_ = 10nF 0 50 in series with COUT_ 0 20 +0.02 300 150 0.25 2 96 96 1 300 40 100 100 100 100 500 +0.75 +0.20 VSS + 1 VSS + 0.75 -20 +2 0.1 10 20 10 25 VDD - 1 VDD - 0.75 +20 V nA ms s nF F nV/Hz % kHz mV V/C dB dB s mA s s s mV SYMBOL CONDITIONS MIN TYP 100 100 100 MAX UNITS s s s
MAX1350-MAX1357
3
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +10V, VSS = 0V, VCS_+ = 30V, COUTCS1, COUTCS2 to CSGND = 10pF, COUT1, COUT2 to DRGND = 10nF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Sense Supply Current VDD to VSS Voltage Range VSS to DRGND Voltage Range Shutdown Supply Current SYMBOL ICS+ VDS VSG SHDN = DRGND (Note 8), TA = +25C TA = +85C CONDITIONS VOUTCS_ = 200mV VOUTCS_ = 2.5V 4.75 -1 0.1 2.5 MIN TYP 135 320 MAX 195 450 11.00 0 1 10 UNITS A V V A
Note 1: Input deliberately offset by 3mV for nulling purposes. Note 2: The output does not reverse phase when overdriven. VSENSE = VCS+ - VCS-. Note 3: Total output voltage error = ((VOUTMEASURED - VOUT-IDEAL) / VOUT-IDEAL) x 100% Total output voltage error = ((Total offset voltage error + total gain voltage error) / VOUT-IDEAL) x 100% where: VOUT-IDEAL = (VSENSE + 3mV) x 2 for the MAX1350/MAX1351 VOUT-IDEAL = VSENSE x 2 for the MAX1352/MAX1353 VOUT-IDEAL = VSENSE x 10 for the MAX1354/MAX1355 VOUT-IDEAL = (VSENSE + 3mV) x 10 for the MAX1356/MAX1357 Note 4: For the MAX1350-MAX1353, the minimum CS_+ to OUTCS_ voltage is 2.494V. For the MAX1354-MAX1357, the minimum CS_+ to OUTCS_ voltage is 2.75V. Note 5: Adding a capacitor (COUTCS) to CSGND at OUTCS_ can limit the bandwidth below that of the sense amplifier by introducing a pole at fPOLE, where fPOLE = 1 / (2 x ROUTCS x COUTCS). For example, for ROUTCS_ = 12.5k, adding a 100pF capacitor introduces a pole at 127kHz (40%). This can be of benefit if noise needs to be restricted or the signal digitized. Note 6: For the MAX1350/MAX1352/MAX1354/MAX1356, the voltage input range is 0.18V VIN VDD / 2. For the MAX1351/MAX1353/ MAX1355/MAX1357, the voltage input range is 0.18V VIN VDD / 4. Note 7: Measured with all the digital inputs low, except SHDN, and no load. Note 8: All digital inputs low. Any digital input consumes current if left in a high state.
Typical Operating Characteristics
(VDD = 10V, VSS = 0, VCS+ = 30V, VSENSE = 100mV, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1350 toc01
SUPPLY CURRENT vs. TEMPERATURE
MAX1350 toc02
SENSE-AMPLIFIER TOTAL OUTPUT VOLTAGE ERROR vs. SUPPLY VOLTAGE
TOTAL OUTPUT VOLTAGE ERROR (%) 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01
MAX1350 toc03
5.50 5.25 5.00 IDD (mA)
7
0.10
6 IDD (mA)
4.75 4.50 4.25 4.00 3.75 3.50 4 5 6 7 8 9 10 11 VDD (V)
5
4
3 -40 -15 10 35 60 85 TEMPERATURE (C)
0 4 5 6 7 8 9 10 11 VDD (V)
4
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers
Typical Operating Characteristics (continued)
(VDD = 10V, VSS = 0, VCS+ = 30V, VSENSE = 100mV, TA = +25C, unless otherwise noted.)
SENSE-AMPLIFIER TOTAL OUTPUT VOLTAGE ERROR vs. SENSE VOLTAGE
MAX1350 toc04
MAX1350-MAX1357
SENSE-AMPLIFIER TOTAL OUTPUT VOLTAGE ERROR vs. COMMON-MODE VOLTAGE
MAX1350 toc05
SENSE-AMPLIFIER TOTAL OUTPUT VOLTAGE ERROR vs. TEMPERATURE
TOTAL OUTPUT VOLTAGE ERROR (%) 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
MAX1350 toc06
4 TOTAL OUTPUT VOLTAGE ERROR (%)
0.10 TOTAL OUTPUT VOLTAGE ERROR (%) 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01
0.5
3
2
1
0
-1 0 0.25 0.50 0.75 1.00 1.25 VSENSE (V)
0 5 10 15 20 VCM (V) 25 30
-40
-15
10
35
60
85
TEMPERATURE (C)
SENSE-AMPLIFIER TRANSIENT RESPONSE
MAX1350 toc07
SENSE-AMPLIFIER GAIN vs. FREQUENCY
MAX1350 toc08
DRIVE-AMPLIFIER OFFSET VOLTAGE vs. TEMPERATURE
MAX1350 toc09
10 5 0 GAIN (dB) -5 -10 -15 -20
350 300 OFFSET VOLTAGE (V) 250 200 150 100 50
VSENSE 1V/div 0
VOUTCS_ 1V/div 0 100s/div
100
1k
10k
100k
1M
10M
-40
-15
10
35
60
85
FREQUENCY (Hz)
TEMPERATURE (C)
DRIVE-AMPLIFIER GAIN ERROR vs. TEMPERATURE
MAX1350 toc10
DRIVE-AMPLIFIER TRANSIENT RESPONSE
MAX1350 toc11
DRIVE-AMPLIFIER GAIN vs. FREQUENCY
VIN 5V/div 0 GAIN (dB)
MAX1350 toc12
0.040 0.035 0.030 GAIN ERROR (%) 0.025 0.020 0.015 0.010 0.005 0 -40 -15 10 35 60
10 5 0 -5 -10 -15 -20
VOUT_ 5V/div 0
85
100s/div
100
1k
10k
100k
1M
10M
TEMPERATURE (C)
FREQUENCY (Hz)
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
Pin Description
PIN MAX1350 MAX1351 MAX1356 MAX1357 1 2 3 4 5 6 7 8 9 10 11 12 13 MAX1352- MAX1355 1, 2, 8 -- 3 4 5 6 7 -- 9 10 11 12 13 NAME FUNCTION
N.C. CAL1 SHDN OUTCS1 IN1 IN2 OUTCS2 CAL2 CSGND DRGND VSS VDD CLAMP2
No Connection. Not internally connected. Offset Calibration Digital Input 1. Drive CAL1 high to short CS1- to CS1+ for input offset nulling. Drive CAL1 low for normal operation. Shutdown Digital Input. Drive SHDN low to place device in low-power shutdown. Drive SHDN high for normal operation. Current-Sense Amplifier Voltage Output 1. VOUTCS1 = AS x (VCS1+ - VCS1-). Drive Amplifier 1 Input Drive Amplifier 2 Input Current-Sense Amplifier Voltage Output 2. VOUTCS2 = AS x (VCS2+ - VCS2-). Offset Calibration Input 1. Drive CAL2 high to short CS2- to CS2+ for input offset nulling. Drive CAL2 low for normal operation. Current-Sense Ground. Ground reference for the current-sense amplifier outputs. Drive Amplifier Ground. Ground reference for the drive amplifier outputs and digital inputs. Negative Drive Power Input. Bypass with a 0.1F capacitor to DRGND. Positive Drive Power Input. Bypass with a 0.1F capacitor to DRGND. Output 2 Clamp Control Input. Drive CLAMP2 high to clamp OUT2 to DRGND. Drive CLAMP2 low for normal operation. Current-Sense Positive Input 2/Sense-Amplifier Power Input. CS2+ is the power connection to the external sense resistor and supplies power to the sense amplifier. For normal operation of the MAX1350-MAX1357, CS1+ and CS2+ must both be in the specified common-mode range. Current-Sense Negative Input 2. CS2- is the load connection to the external sense resistor. See the typical operating circuit. Drive Amplifier 2 Output. VOUT2 = AD x VIN2. Drive Amplifier 1 Output. VOUT1 = AD x VIN1. Current-Sense Negative Input 1. CS1- is the load connection to the external sense resistor. See the typical operating circuit. Current-Sense Positive Input 1/Sense-Amplifier Power Input. CS1+ is the power connection to the external sense resistor and supplies power to the sense amplifier. For normal operation of the MAX1350-MAX1357, CS1+ and CS2+ must be in the specified common-mode range. Output 1 Clamp Control Input. Drive CLAMP1 high to clamp OUT1 to DRGND. Drive CLAMP1 low for normal operation.
14
14
CS2+
15 16 17 18
15 16 17 18
CS2OUT2 OUT1 CS1-
19
19
CS1+
20
20
CLAMP1
6
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers
Functional Diagrams
MAX1350-MAX1357
SHDN
VDD
VSS
SHDN
VDD
VSS
CS1+
CS1+
AS OUTCS1 CS1OUTCS1
AS CS1-
CAL1
IN1
AD
OUT1
IN1
AD
OUT1
CLAMP1
CLAMP1
IN2
AD
OUT2
IN2
AD
OUT2
CLAMP2 CS2+
CLAMP2 CS2+
AS OUTCS2 CS2OUTCS2
AS CS2-
CAL2
MAX1350 MAX1351 MAX1356 MAX1357
CSGND DRGND CSGND
MAX1352-MAX1355
DRGND
AS: SENSE-AMPLIFIER VOLTAGE GAIN AS = 2 FOR THE MAX1350/MAX1351 AS = 10 FOR THE MAX1356/MAX1357 AD: DRIVE-AMPLIFIER VOLTAGE GAIN AD = 2 FOR THE MAX1350/MAX1356 AD = 4 FOR THE MAX1351/MAX1357
AS: SENSE-AMPLIFIER VOLTAGE GAIN AS = 2 FOR THE MAX1352/MAX1353 AS = 10 FOR THE MAX1354/MAX1355 AD: DRIVE-AMPLIFIER VOLTAGE GAIN AD = 2 FOR THE MAX1352/MAX1354 AD = 4 FOR THE MAX1353/MAX1355
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7
Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
10V 0.1F 5V TO 32V
VDD 5V
CS2+ CS2-
SHDN
CS1+
RSENSE AS ADC C LOAD CONTROL OUTCS1 CS1ILOAD
DAC
IN1
AD
OUT1
VARIABLE LOAD
CLAMP2 IN2 CLAMP1 CAL1* CAL2* VSS CSGND DRGND
OUT2
MAX1350-MAX1357
*MAX1350/MAX1351/MAX1356/MAX1357 ONLY
Figure 1. Typical Operating Circuit
Detailed Description
Each of the MAX1350-MAX1357 parts includes two high-side current-sense amplifiers and two drive amplifiers. The current-sense amplifiers are unidirectional and provide a 5V to 32V input common-mode range. For normal operation, the device requires a 4.75V to 11V supply at VDD and a 5V to 32V supply at CS1+ and CS2+. Both CS1+ and CS2+ must be within the specified common-mode range for proper operation of all amplifiers. The CS1+ and CS2+ inputs function as power inputs to the sense amplifier and each typically draws 320A with a full-scale sense voltage (see the Electrical Characteristics).
8
Current-Sense Amplifiers
The sense amplifiers measure the load current, ILOAD, through an external sense resistor, RSENSE, between the CS_+ and CS_- inputs. The sense voltage range (VSENSE = VCS_+ - VCS_-) is between 2mV and 1250mV for the MAX1350-MAX1353 and between 2mV and 500mV for the MAX1354-MAX1357. The sense amplifiers provide a voltage output at OUTCS1 and OUTCS2, where the output voltage is determined by the following equation: VOUTCS_ = AS x (VCS_+ - VCS_-)
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Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers
Offset Calibration (CAL1 and CAL2) The MAX1350/MAX1351/MAX1356/MAX1357 offer a typical input offset voltage of 3mV for systems requiring offset nulling. For the MAX1352-MAX1355, where the nominal input offset voltage is 0, only positive offset is detectable since the output cannot go below ground. With the deliberate input offset voltage of 3mV, the output offset voltage (AS x 3mV) can be easily nulled using external circuitry. Nulling out the sense-amplifier offset significantly improves the total output voltage error at sense voltages below 100mV. Drive CAL_ high to short CS_+ and CS_- together to measure the offset at OUTCS_. Drive CAL_ low for normal operation. The width of the CAL_ pulse should be greater than 40s. Sample OUTCS1/OUTCS2 until 40s after the digital inputs have gone low. input (IN_) to DRGND and drive the associated CLAMP_ high to force the outputs to DRGND.
MAX1350-MAX1357
Applications Information
Application Example--Base-Station LDMOS Bias
The MAX1350-MAX1357 can be used to sense and control the drain current in an LDMOS transistor in base-station applications (see Figure 2). As the temperature of the LDMOS changes, the gate-to-source threshold voltage changes, resulting in an increase or decrease in drain current if the gate bias voltage is fixed. The MAX1350-MAX1357 allow for a softwarecontrollable scheme to sense the LDMOS drain current and adjust the gate bias voltage to compensate for the temperature shift. The circuit in Figure 2 can control up to eight LDMOS transistors when using four MAX1350-MAX1357 devices. The MAX1230 is a 12-bit, 16-channel ADC, which processes up to eight drain current measurements and eight LDMOS temperature measurements (one for each transistor). The MAX5306 is a 12-bit, octal DAC, which controls up to eight gate-drive amplifiers. The digital inputs are controlled using a 5V microcontroller.
Drive Amplifiers
The MAX1350-MAX1357 include dual drive amplifiers with an internally fixed gain (A D ) of 2 for the MAX1350/MAX1352/MAX1354/MAX1356 and 4 for the MAX1351/MAX1353/MAX1355/MAX1357. Output Clamp to DRGND (CLAMP1 and CLAMP2) The MAX1350-MAX1357 offer an output clamp feature for the drive amplifiers. Drive CLAMP1 and CLAMP2 high to clamp OUT1 and OUT2 respectively to DRGND. The CLAMP_ high to OUT_ low delay is typically 1s (see the Electrical Characteristics). Drive CLAMP1 and CLAMP2 low for normal operation.
Current-Sense Resistor Selection
Select RSENSE based on the following criteria: 1) Voltage Loss: A high R SENSE value causes the power-source voltage to degrade through I2R loss. For minimal voltage loss, use the lowest possible RSENSE value. 2) Accuracy: A high RSENSE value allows lower currents to be measured more accurately. This is because offsets become less significant when the sense voltage is larger. 3) Efficiency and Power Dissipation: At high current levels, the I2R losses in RSENSE can be significant. Take this into consideration when choosing the resistor value and its power-dissipation rating. Also, the sense resistor's value can drift if it is allowed to heat up excessively. 4) Inductance: Keep inductance low if the current being sensed has a large high-frequency component. Wirewound resistors have the highest inductance, while metal film is somewhat better. Low-inductance metalfilm resistors are also available. Instead of being spiral wrapped around a core, as in metal-film or wire-wound resistors, low-inductance metal film resistors are a straight band of metal and are available in values under 1.
Power-On Reset
After a power-on reset, the MAX1350-MAX1357 are in shutdown regardless of the state of SHDN. Toggle SHDN (provide a low-to-high transition) to take the device out of shutdown mode. SHDN then continues to function as a level-triggered, active-low input. Drive SHDN high for normal operation.
Digital Inputs (SHDN, CLAMP1, CLAMP2, CAL1, CAL2)
Drive the digital inputs with 3.3V or 5V logic. The absolute maximum voltage that can be applied to these inputs is 6V.
Unused Devices
Figure 1 illustrates an example in which the MAX1350-MAX1357 facilitate current control to a variable load. If using only one of the current-sense amplifiers, connect CS_+ and CS_- of the unused amplifier to the same point as CS_+ of the active sense amplifier. This ensures that the unused CS_+ input resides in the common-mode range for proper operation, and the amplifier output is zero since CS_+ and CS_- are shorted together. For an unused drive amplifier, connect the
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9
Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
10V 0.1F 32V
VDD CS1+ CF** RSENSE RF**
MAX1230
LDMOS 1 TEMPERATURE LDMOS 2 TEMPERATURE ADC ADC OUTCS1
AS
CS1-
ADC
ADC CS2+ CF** AS OUTCS2 CS2RF** RSENSE
MAX5306
DAC IN1 AD
OUT1 RF OUT RF IN LDMOS 1
DAC IN2 AD OUT2
RF OUT 5V CLAMP1 CLAMP2 C CAL1* CAL2* SHDN VSS CSGND DRGND RF IN LDMOS 2
MAX1350-MAX1357
*MAX1350/MAX1351/MAX1356/MAX1357 ONLY **SELECT RF AND CF BASED ON DESIRED FILTER CUTOFF FREQUENCY, WHERE fCUTOFF = 1 / (2 RF x CF). LIMIT RF TO 100 TO MINIMIZE OFFSET ERRORS.
Figure 2. LDMOS Biasing Application 10 ______________________________________________________________________________________
Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
HIGH-CURRENT PATH INPUT 0.3in COPPER RSENSE 0.1in COPPER LOAD 0.3in COPPER SENSE RESISTOR CS_+ CS_-
MAX1350-MAX1357
MAX1350-MAX1357
Figure 3. Using PC Board Trace for RSENSE
Figure 4. Kelvin Connects for Sense Resistors
5) Cost: If the cost of RSENSE is an issue, it may be preferable to use an alternative solution, as shown in Figure 3. This solution uses the PC board traces to create a sense resistor. Because of the inaccuracies of the copper resistor, the full-scale current value must be adjusted with a potentiometer. Also, copper's resistance temperature coefficient is relatively high (approximately 0.4%/C). Using a PC Board Trace to Create a Sense Resistor In Figure 3, assume that the load current to be measured is 10A using a 0.3in-wide, 2oz copper trace. The resistance of 0.1in-wide, 2oz (70m thickness) copper is 30m/ft. For 10A, select RSENSE = 5m for a 50mV drop at full scale. This resistor requires approximately 2in of 0.1in-wide copper trace.
High-Current Measurement
The MAX1350-MAX1357 can achieve high-current measurements by using low-value sense resistors, which can be paralleled to further increase the currentsense limit (see Figure 3). As an alternative, PC board traces can be adjusted over a wide range. Minimize the trace length and ensure accurate sensing with Kelvin connections (see Figure 4).
Power Supply Bypassing and Layout Considerations
Bypass VDD and VSS to DRGND each with at least a 0.1F ceramic capacitor as close to pins as possible to isolate the device for supply-voltage transients. Bypass CS1+ and CS2+ to CSGND each with at least a 0.1F ceramic capacitor as close to the pins as possible. For optimum performance, separate the CSGND and DRGND planes. Use a star-ground configuration and connect the two ground planes together through a lowvalue resistor.
Selector Guide
PART MAX1350 MAX1351 MAX1352 MAX1353 MAX1354 MAX1355 MAX1356 MAX1357 SENSEAMPLIFIER GAIN (AS) 2 2 2 2 10 10 10 10 SENSE-AMPLIFIER INPUT OFFSET VOLTAGE (mV) 3 3 0 0 0 0 3 3 DRIVEAMPLIFIER GAIN (AD) 2 4 2 4 2 4 2 4
Chip Information
TRANSISTOR COUNT: 804 PROCESS: BiCMOS
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11
Dual, High-Side, Current-Sense Amplifiers and Drive Amplifiers MAX1350-MAX1357
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.)
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) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
TSSOP4.40mm.EPS

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