19-5930; Rev 0; 6/11 EVALUATION KIT AVAILABLE MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators General Description The MAX34406 is a quad, high-side, unidirectional, current-sense amplifier that offers precision accuracy. It provides analog outputs for each of the four amplifiers that can be routed to an external ADC, and contains four overcurrent comparators with a fixed 1.0V threshold. All four comparators are logically ORed, and the result can be delayed/filtered with an external capacitor before it is fed to a latched common shutdown open-drain output pin. Applications Network Switches/Routers Features SFour Precision Current-Sense Amplifiers SFixed Gains of 25V/V, 50V/V, 100V/V, and 200V/V SLess Than ±600µV of Input Offset SLess Than ±0.6% of Gain Error (T/F/H) or ±0.8% of Gain Error (W) SWide 2.0V to 28V Common Mode Range SAnalog Voltage Outputs for Each Amplifier SIndependent Overcurrent Comparators with Fixed 1.0V Threshold SLow Power Consumption Base Stations S-40NC to +85NC Temperature Range Servers SSmall 24-Pin TQFN (4mm x 4mm) Package Smart Grid Network Systems Ordering Information appears at end of data sheet. Industrial Controls Block Diagram VDD AMPLIFIER 4 ENA POR AMPLIFIER 3 AMPLIFIER 2 AMPLIFIER 1 INx+ INx- 4 4 MAX34406 OR R1 R1 P OR CLR ROUT N CK N 1.0V REFERENCE 4 OUTx GND SHTDN D 5µA 6V CLAMP Q N LATCH THRESHOLD = VDD x 50% 4 OCx CDLY For related parts and recommended products to use with this part, refer to: www.maxim-ic.com/MAX34406.related ����������������������������������������������������������������� Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators ABSOLUTE MAXIMUM RATINGS Voltage Range on INx+ and INxRelative to GND..................................................-0.3V to +30V Voltage Range on VDD Relative to GND..................-0.3V to +6V Voltage Range on Remaining Pins Relative to GND..................................... -0.3V to (VDD + 0.3V) Continuous Power Dissipation (TA = +70NC) TQFN (derate 27.8mW/NC above +70NC)...............2222.2mW OUT1, OUT2, OUT3, OUT4 Short Circuit to GND.....Continuous Operating Junction Temperature Range............ -40NC to +85NC Storage Temperature Range............................. -55NC to +125NC Lead Temperature (soldering, 10s).................................+300NC Soldering Temperature (reflow).......................................+260NC 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 (VINx+ = VINx- = 12V, VSENSE = 0V, TA = -40NC to +85NC, unless otherwise noted. Typical values are TA = +25NC) (Note 1) PARAMETER VDD Operating Range SYMBOL CONDITIONS VDD MIN 2.7 VDD Supply Current IDD (Note 2) Common-Mode Input Range VCM Guaranteed by CMRR 2.0 VINx+ > 2.0V at TA = +25NC 86 Common-Mode Rejection Ratio Input Offset Voltage CMRR VOS (Note 3) Gain Error G GE OUTx Output Resistance OUTx Low Voltage ROUTx VOL 50 MAX34406H 100 MAX34406W 200 MAX34406W MAX34406T/F/H MAX34406W V 200 FA 28 V dB Q600 10 (Note 5) 15 MAX34406F 30 MAX34406H 60 MAX34406H % kω 20 MAX34406T MAX34406F FV V/V Q0.8 mV 120 MAX34406T BW 5.5 Q0.6 (Note 4) MAX34406W Bandwidth UNITS 25 MAX34406F MAX34406T/F/H MAX 120 Q100 MAX34406T Gain (0.5V < VOUTx < 1.5V) TYP 125 60 VOUTx = 2.0V (Note 5) kHz 30 MAX34406W 15 ENA Input Logic-High VIH VDD x 0.7 VDD + 0.3 V ENA Input Logic-Low VIL VGND 0.3 VDD x 0.3 V Q1 FA 0.3 V ENA Input Leakage Output Logic-Low (SHTDN, OCx) VOL IOL = 2mA ����������������������������������������������������������������� Maxim Integrated Products 2 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators ELECTRICAL CHARACTERISTICS (continued) (VINx+ = VINx- = 12V, VSENSE = 0V, TA = -40NC to +85NC, unless otherwise noted. Typical values are TA = +25NC) (Note 1)x PARAMETER SYMBOL Output Leakage (SHTDN, OCx) CONDITIONS MIN TYP IO Comparator Threshold VTH 0.98 1.00 MAX UNITS Q1 FA 1.02 V Q5 mV Comparator Offset VCOS Comparator Hysteresis VHYS 20 mV tD 3 Fs Comparator Propagation Delay SHTDN Delay Overdrive = Q50mV, output load = 2mA tDLY VDD = 3.3V, CCDLY = 10nF, RBLEED = 10Mω 3.3 VDD = 3.3V, CCDLY = 22nF, RBLEED = 10Mω 7.3 VDD = 3.3V, CCDLY = 33nF, RBLEED = 10Mω 11 VDD = 5.0V, CCDLY = 10nF, RBLEED = 10Mω 5 VDD = 5.0V, CCDLY = 22nF, RBLEED = 10Mω 11 VDD = 5.0V, CCDLY = 33nF, RBLEED = 10Mω 16 ms All devices are 100% production tested at TA= +25NC. All temperature limits are guaranteed by design. VOUT1, VOUT2, VOUT3, VOUT4 = 0V. All open-drain outputs left disconnected. VOS is extrapolated from measurements for the gain-error test. Gain error is calculated by applying two values of VSENSE and calculating the error of the slope vs. the ideal: Gain = 100, VSENSE is 5mV and 15mV. Note 5: The device is stable for any external capacitance value. Note Note Note Note 1: 2: 3: 4: Typical Operating Characteristics (VINx+ = VINx- = 12V, TA = +25°C, unless otherwise noted.) 14 12 10 8 6 4 140 120 VOLTAGE (mV) 20 % OF POPULATION (%) 16 160 MAX34406 toc02 MAX34406 toc01 18 % OF POPULATION (%) VOL vs. IOL +25°C GAIN ERROR 25 15 10 MAX34406 toc03 +25°C INPUT OFFSET 20 OC1 100 80 60 SHTDN 40 5 20 2 0 0 0 -200 -150 -100 -50 0 OFFSET (µV) 50 100 150 -0.15 -0.10 -0.05 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 GAIN ERROR (%) CURRENT IN (mA) ����������������������������������������������������������������� Maxim Integrated Products 3 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators Typical Operating Characteristics (continued) ((VINx+ = VINx- = 12V, TA = +25°C, unless otherwise noted.) INPUT OFFSET vs. COMMON-MODE VOLTAGE 0 -10 -20 -20 -30 -40 5 10 15 20 25 0.2 0.1 -0.1 -60 30 -40 -15 10 35 60 5 0 85 10 15 20 25 COMMON-MODE VOLTAGE (V) TEMPERATURE (°C) COMMON-MODE VOLTAGE (V) GAIN ERROR vs. TEMPERATURE SMALL-SIGNAL GAIN vs. FREQUENCY (GAIN = 100) SMALL-SIGNAL PULSE RESPONSE (GAIN = 100) 50 MAX34406 toc07 0.5 0.4 45 40 30 MAX34406 toc09 MAX34406 toc08 0 0.3 0 -50 -30 MAX34406 toc06 0.4 GAIN ERROR (%) 10 0.5 MAX34406 toc05 -10 INPUT OFFSET (µV) 20 INPUT OFFSET (µV) 0 MAX34406 toc04 30 10mV 5mV VSENSE 35 0.3 GAIN (dB) GAIN ERROR (%) GAIN ERROR vs. COMMON-MODE VOLTAGE INPUT OFFSET vs. TEMPERATURE 0.2 30 1.0V 25 20 VOUTx 15 0.1 10 0.5V 5 0 -15 10 35 60 0 85 10 1 TEMPERATURE (°C) 100 LARGE-SIGNAL PULSE RESPONSE (GAIN = 100) COMPARATOR THRESHOLD vs. TEMPERATURE MAX34406 toc10 25mV 2.5V VOUTx 3.0 1.02 1.01 1.00 0.99 0.98 0.5V CCDLY = 10nF 3.5 SHTDN DELAY (ms) 5mV 1.03 THRESHOLD (V) VSENSE SHTDN DELAY vs. TEMPERATURE 4.0 MAX34406 toc11 1.05 1.04 2.5 2.0 1.5 1.0 0.97 0.5 0.96 20µs/div 20µs/div 1000 FREQUENCY (kHz) MAX34406 toc12 -40 0.95 -40 -15 10 35 TEMPERATURE (°C) 60 85 0 -45 -15 10 35 60 85 TEMPERATURE (°C) ����������������������������������������������������������������� Maxim Integrated Products 4 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators IN4- OUT4 OUT3 IN3- IN3+ TOP VIEW IN4+ Pin Configuration 18 17 16 15 14 13 VDD 19 12 OC4 ENA 20 11 OC3 10 OC2 9 OC1 8 N.C. 7 N.C. SHTDN 21 MAX34406 CDLY 22 N.C. 23 EP + 1 2 3 4 5 6 IN1+ IN1- OUT1 OUT2 IN2- IN2+ GND 24 TQFN (4mm x 4mm) Pin Description PIN NAME FUNCTION 1 IN1+ External Sense Resistor Power-Side Connection for Amplifier 1. Bias at this pin also provides the supply voltage for amplifier 1. This pin can be left open circuit if not needed. 2 IN1- External Sense Resistor Load-Side Connection for Amplifier 1 3 OUT1 Output Voltage from Amplifier 1 Proportional to VSENSE. This output is clamped at 6V. 4 OUT2 5 IN2- Output Voltage from Amplifier 2 Proportional to VSENSE. This output is clamped at 6V. External Sense Resistor Load-Side Connection for Amplifier 2 6 IN2+ External Sense Resistor Power-Side Connection for Amplifier 2. Bias at this pin also provides the supply voltage for amplifier 2. This pin can be left open circuit if not needed. 7, 8, 23 N.C. No Connection. Not internally connected. 9 OC1 Overcurrent Threshold Comparator Associated with Amplifier 1. Open-drain output. This output transitions to high impedance during an overcurrent event. 10 OC2 Overcurrent Threshold Comparator Associated with Amplifier 2. Open-drain output. This output transitions to high impedance during an overcurrent event. 11 OC3 Overcurrent Threshold Comparator Associated with Amplifier 3. Open-drain output. This output transitions to high impedance during an overcurrent event. 12 OC4 Overcurrent Threshold Comparator Associated with Amplifier 4. Open-drain output. This output transitions to high impedance during an overcurrent event. 13 IN3+ External Sense Resistor Power-Side Connection for Amplifier 3. Bias at this pin also provides the supply voltage for amplifier 3. This pin can be left open circuit if not needed. ����������������������������������������������������������������� Maxim Integrated Products 5 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators Pin Description (continued) PIN NAME FUNCTION 14 IN3- 15 OUT3 External Sense Resistor Load-Side Connection for Amplifier 3 16 OUT4 17 IN4- External Sense Resistor Load-Side Connection for Amplifier 4 18 IN4+ External Sense Resistor Power-Side Connection for Amplifier 4. Bias at this pin also provides the supply voltage for amplifier 4. This pin can be left open circuit if not needed. 19 VDD Supply Voltage for Reference, Comparators, and Logic. A +2.7V to +5.5V supply. This pin should be decoupled to GND with a 100nF ceramic capacitor. 20 ENA SHTDN Enable Input. CMOS digital input. Connect to GND to clear the latch and unconditionally deassert (force low) the SHTDN output. Connect to VDD to enable normal latch operation of the SHTDN output. ENA should be toggled low once VDD reaches nominal operating voltage. 21 SHTDN Shutdown Output. Open-drain output. This output transitions to high impedance when any of the four overcurrent comparator outputs (OC1 to OC4) are asserted (high impedance) as long as the ENA pin is high. Toggling the ENA pin allows SHTDN to reset to logic-low. Output Voltage from Amplifier 3 Proportional to VSENSE. This output is clamped at 6V. Output Voltage from Amplifier 4 Proportional to VSENSE. This output is clamped at 6V. 22 CDLY Shutdown Delay Capacitor. A capacitor (CCDLY) from this pin to GND delays the transition of the SHTDN pin. The delay time can be calculated by the following formula: tDLY = CCDLY x (VDD/10FA). The capacitor connected to CDLY is discharged when ENA is low and also upon VDD being applied (i.e., at power-on reset). A shunt resistor, RBLEED, with a max of 22mI, is required to be connected in parallel with the CCDLY capacitor. If the shutdown delay is not required, this pin can be left unconnected. 24 GND Ground Reference — EP Exposed Pad. Connect to ground or leave unconnected. ����������������������������������������������������������������� Maxim Integrated Products 6 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators Typical Application Circuit V1 VDD IN1+ VDD RSENSE1 GND IN1ENA VDD V2 IN2+ RPU RSENSE2 SHTDN IN2- VDD MAX34406 V3 RPU IN3+ OC1 RSENSE3 OC2 IN3- µC OC3 OC4 OUT1 V4 IN4+ OUT2 ADC INPUTS OUT3 OUT4 RSENSE4 IN4- CDLY CCDLY RBLEED (LESS THAN 22mΩ) ����������������������������������������������������������������� Maxim Integrated Products 7 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators Detailed Description The MAX34406 quad-channel, unidirectional, high-side, current-sense amplifier features a 2.0V to 28V input common-mode range. This feature allows the monitoring of current out of a voltage supply as low as 2.0V. The device monitors current through a current-sense resistor and amplifies the voltage across that resistor. Current-sense amplifier output voltages (OUT1 to OUT4) are compared to a fixed 1.0V reference; if VOUTx exceeds 1.0V, the corresponding overcurrent warning output (OC1 to OC4) is asserted. If the enable input (ENA) is logic-high, SHTDN asserts when any of the four overcurrent outputs go logic-high. Assertion of SHTDN on overcurrent can be delayed and/or filtered by attaching an external capacitor to CDLY. Once SHTDN is latched high impedance, it remains so until ENA is toggled. The unidirectional current-sense amplifiers used in each channel of the device have a well established history. For each channel, an op amp is used to force the current through an internal gain resistor at IN+, which has a value of R1, such that its voltage drop equals the voltage drop across an external sense resistor, RSENSE. There is an internal resistor at IN- with the same value as R1 to minimize offset voltage. The current through R1 is sourced by a high-voltage p-channel FET. Its source current is the same as its drain current, which flows through a second gain resistor, ROUTx. This produces an output voltage, VOUTx, whose magnitude is ILOAD x RSENSE x ROUTx/R1. The gain accuracy is based on the matching of the two gain resistors, R1 and ROUTx (Table 1). Total gain = 25V/V for the MAX34406T, 50V/V for the MAX34406F, 100V/V for the MAX34406H, and 200V/V for the MAX34406W. The output is protected from input overdrive by use of a 6V clamp-protection circuit. Table 1. Internal Gain Setting Resistors (Typical Values) GAIN (V/V) R1 (I) ROUTx (kI) 200 100 20 100 100 10 50 200 10 25 400 10 Applications Information Choosing the Sense Resistor Choose RSENSE based on the criteria detailed in the following sections. Voltage Loss A high RSENSE value causes the power-source voltage to drop due to IR loss. For minimal voltage loss, use the lowest RSENSE value. OUTx Swing vs. VINx+ and VSENSE The device is unique because the supply voltage for the current-sense amplifier in each channel is the input common-mode voltage for that channel (the average voltage at INx+ and INx-). There are no separate supply voltage pins for the current-sense amplifiers. Therefore, the OUTx voltage swing for a given channel is limited by the minimum voltage at IN+ for that channel. VOUTx(MAX) = VINx+(MIN) - VSENSE(MAX) - VOH and R SENSE = VOUTx (MAX) G × ILOAD (MAX) VSENSE full scale should be less than VOUTx/gain at the minimum INx+ voltage. For best performance with a 3.6V supply voltage, select RSENSE to provide approximately 120mV (gain of 25V/V), 60mV (gain of 50V/V), 30mV (gain of 100V/V), or 15mV (gain of 200V/V) of sense voltage for the full-scale current in each application. These can be increased by use of a higher minimum input voltage. Accuracy In the linear region (VOUTx < VOUTx(MAX)), there are two components to accuracy: input offset voltage (VOS) and gain error (GE). For all variants of the device, VOS = P 600FV (max); gain error is 0.6% (max) for the MAX34406T/F/H or 0.8% (max) for the MAX34406W. Use the linear equation to calculate total error: VOS Error (%) = GE ± × 100 VSENSE where GE is gain error, VSENSE is the voltage across the sense resistor RSENSE, and VOS is offset voltage. A high RSENSE value allows lower currents to be measured more accurately because offsets are less significant when the sense voltage is larger. ����������������������������������������������������������������� Maxim Integrated Products 8 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators 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 (wattage) rating. Also, the sense resistor’s value might drift if it is allowed to heat up excessively. The precision VOS of the device allows the use of small sense resistors to reduce power dissipation and reduce hot spots. Kelvin Connections Because of the high currents that flow through RSENSE, take care to eliminate parasitic trace resistance from causing errors in the sense voltage. Either use a fourterminal current-sense resistor or use Kelvin (force and sense) PCB layout techniques. Minimizing Trace Resistance PCB trace resistance from RSENSE to the INx+ inputs contributes to gain error in the current-sense amplifiers. Care should be taken to minimize this resistance (shown as RTRC in Figure 1). Total gain including error caused by trace resistance can be calculated as follows: G= R OUTx R1 + R TRC For example, assume a gain of 100V/V, as in the MAX34406H. From Table 1, R1 = 100I and ROUTx = 10kI. Then every 10mI of PCB trace resistance adds -0.01% gain error. Optional Output Filter Capacitor When designing a system that uses a sample-and-hold stage in the ADC, the sampling capacitor momentarily loads OUTx and causes a drop in the output voltage. If sampling time is very short (less than a microsecond), consider using a ceramic capacitor across OUTx and GND to hold VOUTx constant during sampling. This also decreases the small-signal bandwidth of the currentsense amplifier and reduces noise at OUTx. Input Filters Some applications of current-sense amplifiers need to measure currents accurately even in the presence of both differential and common-mode ripple, as well as a wide variety of input transient conditions. For example, high-frequency ripple at the output of a switching buck or boost regulator results in a common-mode voltage at the device’s inputs. Alternatively, the fast load-current transients, when measuring at the input of a switching buck or boost regulator, can cause high-frequency differential sense voltages to occur at the device’s inputs, although the signal of interest is the average DC value. Such highfrequency differential sense voltages can result in a voltage offset at the device output. The device allows a method of filtering to help improve performance in the presence of input common-mode voltage and input differential voltage transients. Figure 2 shows a differential input filter. The capacitor CIN between INx+ and INx- along with the resistor RIN between the sense resistor and INx- helps filter against input differential voltages and prevents them from reaching the device. The corner frequency of this filter is determined by the choice of RIN, CIN, and the value of the input resistance at INx- (R1). See Table 1 for R1 values at the different gain options. The value of RIN should be chosen to minimize its effect on the input offset voltage due to the bias current at INx-. RSENSE RSENSE LOAD RTRC INx+ INx- MAX34406 GND Figure 1. Input Trace Resistance RIN CIN INx+ LOAD INx- OUTx MAX34406 OUTx GND Figure 2. Differential Input Filter ����������������������������������������������������������������� Maxim Integrated Products 9 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators RIN x IBIAS contributes to the input voltage offset. IBIAS is typically 0.2FA. Placing RIN at the INx- input voltage does not affect the gain error of the device because the gain is given by the ratio between ROUTx and R1 at INx+. Bidirectional Application Some systems can require a precise bidirectional current-sense amplifier to accurately monitor currents. RSENSE GND Choosing the Delay Capacitor The SHTDN output asserts upon overcurrent detection on any of the 4 channels. OC1 to OC4 are logically ORed together; SHTDN latches the output after some delay. SHTDN latch delay is determined by the following equation: tDLY = CCDLY × (VDD ÷ 10µA) Example CCDLY and tDLY pairs are given in the Electrical Characteristics table. ILOAD IN1+ Measurement of the two separate outputs with respect to GND yields an accurate measure of the bidirectional currents (Figure 3). IN1- IN2+ IN2- VDD = 3.3V MAX34406 OUT1 OUT2 µC ADC INPUTS A discharge resistor, RBLEED, with a max resistance of 22mI, should be added in parallel with CCDLY. The delay capacitor integrates overcurrent events over time; a parallel resistor RBLEED allows the capacitor to discharge over time, thus limiting the integration period. Accumulated voltage from overcurrent events decay through the bleed resistor with time constant: τ = RBLEED × CCDLY Additionally, discharge of accumulated voltage through RBLEED increases the precision of the SHTDN delay time, tDLY. Figure 3. Bidirectional Application PART Ordering Information GAIN (V/V) TEMP RANGE PIN-PACKAGE MAX34406TETG+* 25 -40NC to +85NC 24 TQFN-EP** MAX34406TETG+T* 25 -40NC to +85NC 24 TQFN-EP** MAX34406FETG+* 50 -40NC to +85NC 24 TQFN-EP** MAX34406FETG+T* 50 -40NC to +85NC 24 TQFN-EP** MAX34406HETG+ 100 -40NC to +85NC 24 TQFN-EP** MAX34406HETG+T 100 -40NC to +85NC 24 TQFN-EP** MAX34406WETG+* 200 -40NC to +85NC 24 TQFN-EP** MAX34406WETG+T* 200 -40NC to +85NC 24 TQFN-EP** +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *Future product—contact factory for availability. **EP = Exposed pad. Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 24 TQFN-EP T2444+4 21-0139 90-0022 ���������������������������������������������������������������� Maxim Integrated Products 10 MAX34406 Quad Current-Sense Amplifier with Overcurrent Threshold Comparators Revision History REVISION NUMBER REVISION DATE 0 6/11 DESCRIPTION Initial release PAGES CHANGED — 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. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2011 Maxim Integrated Products 11 Maxim is a registered trademark of Maxim Integrated Products, Inc.