MAX40204ANA+

Click here to ask about the production status of specific part numbers. MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA General Description Benefits and Features The MAX40204 is a high-precision, bidirectional, high-side current-sense amplifier (CSA) with a wide input commonmode range from -0.1V (ground sensing) to 36V. ● ● ● ● ● ● ● ● ● ● ● The device's ultra-low 2μV input offset voltage allows the use of small sense resistor to reduce power dissipation and a very low, 0.05% gain error ensures measurement accuracy. The MAX40204 offers two gain options using a logic-level input (GAIN) that provides the flexibility to change the gain on the fly. On-the-fly gain adjustment capability allows the system to enhance accuracy when measuring current much smaller than set full-scale level. See Table 1 for gain configurations. Additionally, the MAX40204 supports unidirectional and bidirectional current sensing with an external voltage applied to a reference input, REF. The MAX40204 operates with single-supply in the range of 1.7V to 5.5V while consuming only 21μA. Low operating supply current and 70nA (typ) shutdown current help extend battery life and make the MAX40204 ideal for portable and battery-operated devices. The MAX40204 is available in a small 8-bump, 0.35mmpitch WLP (1.468mm x 0.848mm) and 8-pin TDFN (2mm x 2mm) packages and is specified over the -40°C to +125°C extended operating temperature range. Applications ● ● ● ● ● ● Current Sensing in Power Management Systems Portable and Battery-Operated Systems Medical Instruments Base Station Smart Phones and Tablets Notebook Computers 19-100845; Rev 1; 10/20 -0.1V to 36V Wide Input Common Mode Ultra-Low, 2μV Input Offset Voltage On-the-Fly Gain Setting Input Bidirectional/Unidirectional Current Sensing 20nA (max) Input Bias Current Extremely Low, 50nV/°C Input Offset Tempco 0.05% Gain Error 21μA Supply Current 70nA (typ) Shutdown Current 1.7V to 5.5V Single Supply Operating Range Space-Saving 8-Bump WLP and 8-Pin TDFN Packages Ordering Information appears at end of data sheet. MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Typical Application Diagram ILOAD VBATT UP TO 36V RSENSE RS+ RSLOAD 3.3V GND VDD SHDN VDD/2 REF 3.3V GAIN MAX40204 OUT µC I/O ADC www.maximintegrated.com Maxim Integrated | 2 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA TABLE OF CONTENTS General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Typical Application Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 TDFN-CU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8 WLP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8 TDFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8 WLP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Gain Selection Inputs, GAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Shutdown, SHDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Low Offset Voltage and Low Gain Error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Reference Input, REF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Input Differential Signal Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Choosing the Sense Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Kelvin Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Efficiency and Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Input Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Output Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Bidirectional Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Programmable Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Power-Supply Bypassing and Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 www.maximintegrated.com Maxim Integrated | 3 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA LIST OF FIGURES Figure 1. Unidirectional Current-Sensing Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 2. Bidirectional Current-Sensing Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 3. Differential Input Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 4. Input Common-Mode Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 5. Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 6. Bidirectional Current-Sensing Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 7. Low Current Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 8. Input/Output Signal Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 www.maximintegrated.com Maxim Integrated | 4 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA LIST OF TABLES Table 1. Gain-Setting Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Table 2. VSENSE Input Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 www.maximintegrated.com Maxim Integrated | 5 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Absolute Maximum Ratings VDD to GND.............................................................. -0.3V to +6V RS+ to RS- ........................................................................... ±40V RS+, RS- to GND ................................................... -0.3V to +40V GAIN, REF, OUT, SHDN to GND ................ -0.3V to VDD + 0.3V Continuous Input Current (any pin) ..................................... 10mA WLP Package Continuous Power Dissipation (Multilayer Board) (TA = +70°C, derate 10.90mW/°C above +70°C) ............. 872mW TDFN Package Continuous Power Dissipation (Multilayer Board) (TA = +70°C, derate 11.70mW/°C above +70°C) ........936.90mW Operating Temperature Range ...........................-40°C to +125°C Junction Temperature ....................................................... +150°C Storage Temperature Range ..............................-40°C to +150°C Soldering Temperature (reflow) ........................................ +260°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. www.maximintegrated.com Maxim Integrated | 6 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Package Information TDFN-CU Package Code T822+3C Outline Number 21-0168 Land Pattern Number 90-0065 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) N/A Junction to Case (θJC) N/A Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 85.30°C/W Junction to Case (θJC) 8.9°C/W www.maximintegrated.com Maxim Integrated | 7 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA 8 WLP Package Code N80E1+1 Outline Number 21-100451 Land Pattern Number Refer to Application Note 1891 Thermal Resistance, Single-Layer Board: Junction to Ambient (θJA) N/A Junction to Case (θJC) N/A Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 91.71°C/W Junction to Case (θJC) N/A www.maximintegrated.com Maxim Integrated | 8 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/ thermal-tutorial. www.maximintegrated.com Maxim Integrated | 9 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Electrical Characteristics (VDD = VSHDN = 1.8V, VRS+ = VRS- = +12V, VSENSE = (VRS+ - VRS-) = 50mV, G = 10V/V, VREF = 0.9V, RL = 10kΩ to GND, TA = -40°C to +125°C, unless otherwise noted. Typical values are at +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V -40ºC ≤ TA ≤ +85ºC 70 300 -40ºC ≤ TA ≤ +125ºC 70 800 TA = +25°C 21 31 µA -40°C ≤ TA ≤ +125°C 21 41 µA POWER SUPPLY Supply Voltage Range Shutdown Supply Current Supply Current Power-Supply Rejection Ratio VDD ISHDN IDD PSRR Guaranteed by PSRR No load 1.7 G = 10V/V 100 110 G = 100V/V 100 110 nA dB Turn-On Time tEN Turn-on from shutdown, measured at 90% of nominal final value 400 µs Power-On Time tON VDD = 0 to 1.8V, measured at 90% of nominal final value 400 μs VCM Guaranteed by CMRR -0.1 G = 10V/V 110 140 G = 100V/V 110 140 DC CHARACTERISTICS Input Common-Mode Range Common-Mode Rejection Ratio Input Bias Current Input Offset Current CMRR Gain VSENSE = (VRS+ - VRS-) = 0V 1 20 nA VSENSE = (VRS+ - VRS-) = 0V 0.1 2 nA TA = +25°C 2 20 -40°C ≤ TA ≤ +125°C 2 35 TA = +25°C 2 15 -40°C ≤ TA ≤ +125°C 2 30 VOS TCVOS G Gain Selection Settling Time (Note 1) GE G = 100V/V μV 50 nV/°C VGAIN = low 10 V/V VGAIN = high 100 V/V 0.2 ms VOUT to settle within ±100mV G = 10V/V Gain Error dB IB GAIN = 100V/V Input Offset Drift V IOS GAIN = 10V/V Input Offset Voltage 36 TA = +25°C 0.05 0.15 -40°C ≤ TA ≤ +125°C 0.05 0.30 TA = +25°C 0.05 0.15 -40°C ≤ TA ≤ +125°C 0.05 0.30 % Output-Voltage High VOH VOH = VDD - VOUT, ISOURCE = 100μA 20 mV Output-Voltage Low VOL ISINK = 100μA 20 mV Output Impedance www.maximintegrated.com ZOUT 200 mΩ Maxim Integrated | 10 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Electrical Characteristics (continued) (VDD = VSHDN = 1.8V, VRS+ = VRS- = +12V, VSENSE = (VRS+ - VRS-) = 50mV, G = 10V/V, VREF = 0.9V, RL = 10kΩ to GND, TA = -40°C to +125°C, unless otherwise noted. Typical values are at +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS AC CHARACTERISTICS Small-Signal Bandwidth BW3dB Input-Voltage Noise Density VN AC Common-Mode Rejection Ratio CMRRAC Settling Time tS Capacitive Load G = 10V/V 15 G = 100V/V 1.8 f = 100Hz 150 nV/√Hz f = 10kHz, 300mVP-P sinusoidal waveform 80 dB 1,500 µs 500 pF VOUT from 400mV to 1.4V, G = 10V/V and G = 100V/V, within 12-bit accuracy No isolation resistor kHz INPUT REFERENCE Input Reference Voltage Range VREF 0 VDD/2 + 0.1 V DIGITAL INPUTS DC CHARACTERISTICS (SHDN AND GAIN) Input High Voltage VIH Input Low Voltage VIL 1.3 V 0.55 V Note 1: Maximum sense voltage for G = 10V/V: 150mV with VDD > 3V; 100mV with VDD = 1.8V. www.maximintegrated.com Maxim Integrated | 11 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Typical Operating Characteristics www.maximintegrated.com Maxim Integrated | 12 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Typical Operating Characteristics (continued) www.maximintegrated.com Maxim Integrated | 13 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Typical Operating Characteristics (continued) www.maximintegrated.com Maxim Integrated | 14 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Pin Configurations 8 TDFN TOP VIEW GND 1 REF 2 GAIN 3 RS- 4 8 SHDN 7 VDD 6 OUT 5 RS+ MAX40204 EP* 8 TDFN-EP *EXPOSED PAD. CONNECT EP TO SOLID GROUND FOR PROPER THERMAL AND ELECTRICAL PERFORMANCE. 8 WLP TOP VIEW (BUMP SIDE DOWN) MAX40204 1 2 3 4 A RS+ GAIN OUT VDD B RS- REF GND SHDN WLP Pin Description PIN 8 TDFN 8 WLP 1 B3 www.maximintegrated.com NAME GND FUNCTION Ground Maxim Integrated | 15 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Pin Description (continued) PIN 8 TDFN 8 WLP NAME FUNCTION 2 B2 REF Reference Input. Connect REF to an external voltage from 0V to VDD/2 to set the output voltage level of the CSA corresponding to no-measured current. Connect REF to 0V to configure the MAX40204 for unidirectional current sensing. Connect REF to VDD/2 to configure the MAX40204 for bidirectional current-sensing measured current. 3 A2 GAIN Gain Selection Input. Connect GAIN to VDD to set the gain of the CSA to 100V/V. Connect GAIN to GND to set the gain of the CSA to 10V/V. 4 B1 RS- Negative Current-Sensing Input. Connect a sense resistor between RS- and RS+. See the Choosing the Sense Resistor section for more detail. 5 A1 RS+ Positive Current-Sensing Input. Connect a sense resistor between RS+ and RS-. See the Choosing the Sense Resistor section for more detail. 6 A3 OUT Current-Sense Amplifier Output. VOUT is proportional to the sense voltage across the sense resistor connected between RS+ and RS-. 7 A4 VDD Positive Supply Voltage Input. Bypass VDD to GND with 0.1μF and 4.7μF capacitors in parallel as close as possible to the supply voltage input. 8 B4 SHDN Active-Low Shutdown Input. Connect SHDN to GND to place the device in shutdown mode. Connect SHDN to VDD for normal operation. EP — EP www.maximintegrated.com Exposed Pad. Connect to a large-area contiguous ground plane for improved power dissipation. Do not use as the only ground connection for the part. Maxim Integrated | 16 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Detailed Description The MAX40204 is a single-supply, high-accuracy CSA that operates with a wide common-mode input range of -0.1V to 36V independent of the supply voltage (VDD). An external sense resistor connected between RS+ and RS- measures the load current and generates an output signal proportional to the set gain. See [[Gain Setting Connection]] for gain-setting configuration. The MAX40204 offers both unidirectional and bidirectional current-sensing schemes using a reference input (REF). See the Reference Input section for more detail. Low quiescent current of 21μA and 70nA shutdown current extend battery life and make the MAX40204 ideal for many battery-powered applications. The MAX40204's low input offset voltage, tight gain error, and low temperature drift characteristics allow the use of small sense resistors in systems that require high efficiency and accuracy. These features allow monitoring of power-supply load current even if the rail is shorted to ground. High-side current sensing does not interfere with the ground path of the load being measured, making the MAX40204 particularly useful in a wide range of high-reliability systems. In addition, the extended common-mode input range below ground makes the MAX40204 suitable for low-side current sensing. Gain Selection Inputs, GAIN Unlike the available CSAs on the market that offer fixed-gain options, the MAX40204 features an input, GAIN, that provides the flexibility to change the gain on the fly based on its input logic. See Table 1 for more detail. This on-the-fly gain setting capability not only enhances accuracy measurement at the low end of the full-scale input range, but also allows the MAX40204 to be used in multiple applications with different current ranges. For example, a 150mΩ sense resistor used for 1A load applications produces a 150mV full-scale sense voltage between the inputs and 1.5V at the output with a gain of 10V/V. The same sense resistor could be used for 1/10th of load current and provide 1.5V output voltage with a gain of 100V/V. Since the input offset voltage is 2μV, its impact on the accuracy is insignificant for both gain options. Furthermore, the ADC can process both cases with the same resolution. Table 1. Gain-Setting Connection GAIN GAIN (V/V) GND 10 VDD 100 Shutdown, SHDN Shutdown input is an active-low logic input (SHDN) that places the device in the shutdown mode of operation. In shutdown mode, the device enters a very low power mode and consumes only 70nA (typ) of supply current. Drive SHDN high for normal operation. Drive SHDN low to place the device in shutdown mode. Low Offset Voltage and Low Gain Error The MAX40204 utilizes capacitive-coupled chopper instrumentation amplifier (CCIA) architecture to achieve a lowinput offset voltage of 2μV (typ). These techniques also enable extremely low-input offset voltage drift over time and temperature to 50nV/°C. The precision VOS specification allows accurate current measurements with lower values of current-sense resistors, thus reducing power dissipation in battery-powered systems, as well as load-regulation issues in low-voltage DC power supplies. Working with error tolerances with very few internal blocks in this architecture is instrumental in achieving a gain error of less than 0.30% over the entire temperature range of -40°C to +125°C. Reference Input, REF The MAX40204 supports both unidirectional and bidirectional current-sensing operations. Connecting the reference input (REF) to ground configures the MAX40204 for unidirectional current sensing. For unidirectional current sensing, the output is referenced to ground and the output voltage VOUT is proportional to the positive voltage drop (VSENSE) from www.maximintegrated.com Maxim Integrated | 17 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA RS+ to RS-. (See Figure 1 for unidirectional operation.) The MAX40204 operates as a bidirectional CSA by application of a low source impedance reference voltage to REF above ground, typically VDD/2. In the bidirectional current-sensing mode of operation, the output voltage VOUT is referenced to VREF. See Figure 2 for bidirectional operation. VOUT 2.0V RSENSE RS+ ILOAD 1.5V RS- LOAD MAX40204 3.3V G = 100V/V OUT VDD SHDN ILOAD = VOUT/G 1.0V ADC REF 0.5V GND 0 5mV 15mV 10mV 20mV VSENSE Figure 1. Unidirectional Current-Sensing Operation VOUT - VREF G = 100V/V 1.5V ILOAD ICHARGE RSENSE 1.0V RS+ RS- MAX40204 3.3V VDD OUT ADC SHDN REF VDD/2 GND ILOAD = (VOUT - VREF)/G 0.5V LOAD -15mV -10mV -5mV 0 5mV 10mV 15mV VSENSE -0.5V IDISCHARGE = (VREF - VOUT)/G -1.0V -1.5V Figure 2. Bidirectional Current-Sensing Operation www.maximintegrated.com Maxim Integrated | 18 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Applications Information Input Differential Signal Range The MAX40204’s input structure is optimized for sensing small differential signals as low as 17mV full scale (VFS) for high efficiency with lowest power dissipation in the sense resistor, or 150mV full scale for high dynamic range. The input differential signal range is determined by the following equation: VDD V(SENSERANG) = GAIN The input differential voltage range is estimated for VDD from 1.7V to 5.5V using a gain of 100V/V and 10V/V. For a gain of 10V/V, the max VSENSE is 150mV when VDD >3V and 100mV when VDD = 1.7V. (See Table 2.) Ideally, the maximum load current develops the full-scale sense voltage across the current-sense resistor. Choose the gain needed to yield the maximum output voltage required for the application: VOUT = GAIN × VSENSE Table 2. VSENSE Input Range GAIN (V/V) VSENSE RANGE (mV) WITH VDD (1.7V) VSENSE RANGE (mV) WITH VDD (5.5V) 10 100 150 100 17 55 Choosing the Sense Resistor 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. Accuracy Use the following linear equation to calculate total error: VOUT = (GAIN ± GE) × VSENSE ± (GAIN × VOS) A high RSENSE value allows lower currents to be measured more accurately because offsets are less significant when the sense voltage is larger. Note that the tolerance and temperature coefficient of the chosen resistors directly affect the precision of any measurement system. For best performance, select RSENSE to provide approximately maximum input differential sense voltage. Kelvin Connections Because of the high currents that may flow through RSENSE based on the application, be sure to eliminate solder and parasitic trace resistance from causing errors in the sense voltage. Either use a four-terminal current sense resistor or use Kelvin (force and sense) PCB layout techniques. Efficiency and Power Dissipation At high current levels, the I2R losses in RSENSE can be significant. This should be taken into consideration when choosing the resistor value and its power dissipation (wattage) rating. The sense resistor’s value will drift if it is allowed to heat up excessively. The precision VOS of the MAX40204 allows the use of small sense resistors to reduce power dissipation and reduce hot spots. Input Filtering Some applications of CSAs need to measure currents accurately even in the presence of both differential and commonmode ripple, as well as a wide variety of input transient conditions. The MAX40204 allows two methods of filtering to help improve performance in the presence of input common-mode voltage and input differential voltage transients. Figure 3 www.maximintegrated.com Maxim Integrated | 19 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA shows a differential input filter. The capacitor CIN across RS+ and RS- along with the resistor RIN helps filter against input differential voltages and prevents them from reaching the MAX40204. The corner frequency of this filter is determined by the choice of RIN, CIN. Figure 4 shows a common-mode input filter. The choice of capacitance depends on corner frequency after RIN is chosen. In case of mismatch or error in application design, an additional DC error is accumulated as offset voltage and increased gain error. VOS = (RINxIOFFSET) + (DRINxIBIAS) DRIN is the resistance mismatch in RIN at RS+ and RS-. If DRIN is too small, its effect can be neglected. Since IOFFSET of the MAX40204 is smaller than 2nA, and if we want to make sure VOS is less than a 1μV range, choosing: RIN < (VOS ÷ IOFFSET)For gain error, it depends on its input impedance and RIN. − RIN GE = 2 × Z IN Avoid additional gain error shift due to the effect of RIN. For gain error, the MAX40204 is 0.15%. If the margin of additional effect of RIN results in a gain error shift of less than 0.02%, then: 0.02 % RIN < 2xZ = 60Ω IN So RIN can be chosen ≤ 50Ω. RSENSE RIN RIN LOAD CIN RS+ RS- MAX40204 OUT GND Figure 3. Differential Input Filtering www.maximintegrated.com Maxim Integrated | 20 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA RSENSE RIN RIN CIN LOAD CIN RS+ RS- MAX40204 OUT GND Figure 4. Input Common-Mode Filtering Output Filtering The internal architecture of the MAX40204 suppresses the DC offset, 1/f noise, and accumulates at higher frequencies so that they can be filtered out. Hence, minute AC disturbances can be observed at 10kHz and 20kHz. It is recommended to add an output filter after the MAX40204 to avoid noise and unwanted frequency disturbances at the output with 4kHz -3dB fc (see Figure 5). (Suggested values of C and R: 22nF and 1.8kΩ, respectively.) LOAD CIN1 MAX40204 RIN RS- RSENSE R CIN2 RIN OUT RS+ VBATT C CIN1 Figure 5. Filtering Bidirectional Application Battery-powered systems may require a precise bidirectional CSA to accurately monitor the battery’s charge and discharge currents. Measurements of the two separate outputs with respect to GND yield an accurate measure of the charge and discharge currents, respectively (Figure 6). www.maximintegrated.com Maxim Integrated | 21 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA ILOAD RSENSE TO WALL-CUBE CHARGER VBATT UP TO 36V LOAD 3.3V RS- RS+ VDD REF MAX40204 GND VDD = 3.3V OUT µC ADC Figure 6. Bidirectional Current-Sensing Application Programmable Gain The MAX40204 features a logic-level gain input (GAIN) that allows the system to switch between two gain settings—10V/ V and 100V/V—during normal operation. (See the Gain Selection Inputs section for more detail.) Combined with the MAX40204's ultra-low input offset voltage, the on-the-fly programmable-gain capability offers the advantage of adjusting the gain for optimum performance during normal operation, a desirable feature not available in fixed-gain CSAs. Figure 7 shows a typical application with low current range using the MAX40204. Typcally, for a three-decade load range, a 12-bit ADC would be required to ensure the process of true dynamic range of the measuring signal and also allow some margin for other sources of error in the system. But in Figure 7, the system is using a 10-bit ADC because the MAX40204 programmable-gain input allows the system to pump up the input signal in the higher portion of the ADC's dynamic range, thus increasing immunity of the signal to noise and system errors. In Figure 7, the MAX40204 uses a 5Ω resistor to sense the load current, and its output feeds into a 10-bit, ~1.75mV LSB ADC. At a minimum load current of 30μA, the sense resistor generates 150μV across the sense resistor. Taking into account ±10μV(max) input offset voltage, the sensed voltage can vary from 140μV to 160μV, which is only ±6.6% of the measured signal. For this level of current, a gain configuration of 10V/V (VGAIN = GND), is not enough for the ADC to process the input signal. The best gain configuration would be 100V/V (VGAIN = VDD) to boost signal and accurately measure the input signal At a maximum load current of 30mA, the impact of the input offset voltage on the measured signal is even more insignificant: ±0.66%. In this case, however, the 100V/V gain configuration would not be practical due to the output dynamic range limitations dictated by the operating supply voltage of the MAX40204. An accurate signal representation is achieved by using a 10V/V gain configuration, resulting in an output variation range of 1.4895V to 1.5105V. See Figure 8 for more detail. www.maximintegrated.com Maxim Integrated | 22 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA VIN ISENSE 5Ω 1.8V VDD RS+ RS- 30µA ≤ ILOAD ≤ 30mA CSA GND µC GAIN MAX40204 1.8V OUT 10-BIT ADC G = 100V/V AT 30µA LOAD CURRENT G = 10V/V AT 30mA LOAD CURRENT Figure 7. Low Current Application www.maximintegrated.com Maxim Integrated | 23 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA ILOAD 30mA 30µA t1 t2 t VSENSE 15000µV VOS = 0.0066% VOS = 6.6% 150µV t1 t2 t VOUT 1.5V VOS = 0.0066% GAIN = 100V/V 15mV GAIN = 10V/V VOS = 6.6% t1 t2 t Figure 8. Input/Output Signal Representation Power-Supply Bypassing and Grounding Bypass the MAX40204's VDD to ground with a 0.1μF capacitor. Grounding these devices requires no special precautions—follow the same cautionary steps that apply to the rest of the system. High-current systems can experience large voltage drops across a ground plane, and this drop may add to or subtract from VOUT. Using a differential measurement between OUT and REF prevents this problem. For highest current-measurement accuracy, use a singlepoint star ground. Connect the exposed pad to a solid ground to ensure optimal thermal performance. Ordering Information PART NUMBER TEMP RANGE PIN-PACKAGE MAX40204ANA+T -40°C to +125°C 8-Bump WLP MAX40204ATA+T* -40°C to +125°C 8-Pin TDFN-CU +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. *Future product—contact factory for availability. www.maximintegrated.com Maxim Integrated | 24 MAX40204 36V, Pin-Programmable Gain, Bidirectional CSA Revision History REVISION NUMBER REVISION DATE DESCRIPTION 0 9/20 Release for intro 1 10/20 Updated Electrical Characteristics PAGES CHANGED — 10, 11 For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated 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 and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2020 Maxim Integrated Products, Inc.