TP5532 Evaluation Board User's Guide Application Note
Contents
1. Res Res Res Res Res Res Res double opa AD7122. and Protection Features External power connections are made through the V and ground jacks The single supply input is overvoltage protected using a series 1000 R15 resistor and a 5 6V zener diode D1 R15 is used to reduce the overvoltage from power supply D1 is used to protect the chip from overvoltage allows over current flows through it to ground R15 C4 and C2 all works together as a RC low pass filter which filter the noise generated by power supply Reverse polarity protection uses the 1000 resistor and two protection diode pairs D3 D4 These also provide input common mode voltage protection to the op amp Input Protection Clamp Options Included on the evaluation board are optional input protection circuits that illustrate the best methods to limit input common mode and differential transient voltage spikes in exposed or electrically hazardous applications The TP5532 can handle input common mode and differential transients to a diode drop beyond the rails or to a range of 0 5V to 5 5V when operating from a single 5V supply Clamp diodes D3A B D4A B and input resistors R6 R7 R8 R9 form a current limiting 6V common mode and differential voltage clamp This clamp provides sufficient protection for the TP5532 for common mode fault voltages far beyond the power supply rails These diodes also provide the same 6V protection against large differential transients High speed current sensing may involve filterin
3. capacitor C22 2 2uF work as a low pass filter which non inverting amplifier Resistor and allows the signal freguency below 16 8Hz to pass 2 REVO 0 www 3peakic com Application Note TP5532 Capacitor C23 221F and resistor R20 110KQ work as a high pass filter which allows the signal frequency above 0 1Hz to pass The noise can be tested at the terminal OUTB www 3peakic com REVO0 0 1 3 4 B E vi oun RIS MS M IN 1 IN2 R bl SIE 1 65V to 5 5V 4 1000hm 5 vss HN P I SENSE SMB GND Vs 2 reference EXT referente RU VREF jumper jumper Res 499k 2 D3A SE dur MB D Schottky GND Res 100hm co 1 jumper Bis OUTB R20 SNB 110k Res 100hm C9 Res A T GND C7 C2 InF Cap Semi 4 7uF D3B D D Schottky 5 6V gt I SENSE GNDSMB GND GND MB GND Title Size Number Revision A4 Date 2014 3 25 Sheet of File E STUDY TP5532 SchDoc Drawn By 3 4 be Capacitor Cap Semi Semiconductor SIM Model D Schottky Schottky Diode Ze ER a DSO C2 X2 3 D Schottky SMB SMB Straight Connector es R EA Quantity 1 2 EXT reference Vs 2 reference 0603 cap_0603 0603 cap_0603 DSO C2 X3 3 Diode GND I SENSE I SENSE SENSE OUT ME OUTB VREF Vs R1 R2 R4 R5 0805 R6 R7 R8 R9 R10A R10B R11 R12A R12B R13 R14 SMB
4. A 3PEAK Application Note TP5532 TP5532 Evaluation Board User s Guide Description The TP5532 evaluation board contains a complete precision current sense amplifier using the TP5532 chopper amplifier in a high side low side of floating supply current sense application The advantages of the TP5532 in this application include very low offset voltage 2uV typical and offset drift 0 0081 V C rail to rail input and output and low power consumption 341A per Amplifier typical These features provide a very high degree of precision for use in 5V low power applications Evaluation Board Key Features The TP5532 EVB operates from a single 1 8VDC to 5 5VDC supply The current sense function is configured as a single stage balanced input trans impedance amplifier A 0 10 0 1 current sense resistor is used convert the incoming current to a voltage which is applied to a precision differential amplifier with a gain of 100 The overall current to voltage transfer ratio is 10V A and a bidirectional current range of 0 25A is achieved when operating from a 5V supply using a 2 5V reference voltage Vrer At 25 C the TP5532 achieves a total full scale offset error of 0 038 when a precision external reference is used and approximately 0 15 using the internal 0 1 resistors The total current draw from the amplifier power is less than 35yA and the total leakage current from the current sense input is less than 31A Power Supply
5. g repetitive current transients with high peak to average values In these cases limiting these transient even further will improve amplifier response and overload settling time The optional Schottky diode transient clamp D2 reduces transients let through by the common mode clamp from 6V down to 0 3V which Capacitors C7 and C9 provide common mode noise improves overload recovery time filtering and capacitor C8 can be used to filter the current sense signal Current Sense Gain Equations The current sense amplifier in Page 4 forms a trans impedance amplifier whose gain is in units of V A and is determined by the ratios of resistor pairs R11 R8 and R14 R9 Resistor R11 is set equal to R14 and R8 is set equal to R9 This matching cancels the input offset voltage errors caused by the op amp input bias currents www 3peakic com REVO O 1 Application Note TP5532 leaving behind only the offset voltage errors caused by the TP5532 input offset current los The Isense to Vout DC transfer function is given by Equation 1 EQ 1 R14 Vout Isense X RSENSE X VREF where R11 R14 and R6 R8 R7 R9 On the evaluation board the R12 R9 resistor ratio is 100 1 499k0 4 9k0 and Rsense is 0 10 for a trans impedance gain given by Eguation 2 SENSE 10 2 EQ 2 SENSE A Input Range and Offset Error Analysis The TP5532 output swings from rail to rail and the evaluation board has a bi directional
6. output range of VREF 2 5V when operated from a 5V supply and Vrer is set to Vs 2 The jumper selectable internal Vs 2 reference or an external evaluation board contains a reference Vrer pin With Vrer set to 2 5 the full scale output range is O 0 25A The very low offset voltage 21V 25 C max and offset current 100 pA 25 C max of the TP5532 enable the use of very high values resistors for low current consumption while maintaining excellent precision in battery operated circuits The total offset voltage contribution of the TP5532 is the sum of the input offset voltage Vos and the offset voltage produced by the input offset current los through the gain resistors and using the evaluation board resistor values and the data sheet maximum 25 C Vos gives the total input offset voltage as shown in Equations 3 4 and 5 R14xR9 Voscrotal los x Vos EQ 3 R14xR9 Voscrotan 3e 10 x S suv EQ 4 Voscrotal 3e 10 x 4950 81V 9 54V EQ 5 Multiplying the TP5532 input offset voltage by the amplifier gain allows the input offset error to be expressed as a percent of full scale output voltage R14 VosX ko F S Error 0 038 EQ 6 Using the Evaluation Board The evaluation board has separate connections for the amplifier power supply an output zero reference VREF the The inter connection between the Isense terminals and the and current sense terminals correct V
7. rer terminals are needed to implement the different types of current sense configurations The I SENSE and I SENSE measured circuit determine the polarity of the amplifier connections to the output voltage Establishing a current flow from the I SENSE to I SENSE causes the output voltage to increase in proportion to the input current Reversing the I SENSE current flow reverses the output polarity The voltage applied to the Vrer pin defines the amplifier output zero current level and must be between 0V and 5V For bi directional current sensing a reference midway between the ground and the supply voltage will maximize the output span For example a Vrer 2 5V would be the best choice for 5V power supply The jumper selectable internal voltage divider is provided for this internal reference The 2 5V will establish an output current scale setting OA 2 5V but the accuracy is determined by the voltage divider accuracy 0 1 resistors on the evaluation board Connecting the jumper to the external reference position enables an external reference source to be used The TP5532 maintains precision performance from rail to rail making precision ground side sensing possible Additional Feature The TP5532 EVB can be also used for testing noise The R18 R17 resistor ratio is 100 1 499kO 4 9kQ The evaluation board contains a jumper selectable jumper 1 and jumper 2 for choosing either inverting amplifier or R19 4 3kQ
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