Application Note 1531 ISL28005 Evaluation Board User’s Guide Introduction The ISL28005 evaluation board is a design platform containing all the circuitry needed to characterize critical performance parameters of the ISL28005 in either a high side or low-side current sense application. The ISL28005 is available in fixed 100V/V, 50V/V, 20V/V gains. Reference Documents • ISL28005 Data Sheet, FN6973 Evaluation Board Schematic The ISL2800XEVAL1Z evaluation board is configured with either the ISL28005-100, ISL28005-50 or ISL28005-20 device. Figure 1 shows the basic application circuit and optional protection components for the fixed gain parts. Figure 2 shows the complete schematic for the ISL2800XEVAL1Z evaluation board. Components shown in red in Figure 1 are optional transient protection and not required for clean environments. Note: The evaluation board comes equipped with the transient protection devices. Optional Transient Protection For applications where the load and the power source are permanently connected, transient protection is not required and only an external current sense resistor (R3) is needed. For applications where fast transients can generate voltage spikes that can overdrive the amplifier input and drive the output of the amplifier into the rails, resulting in a long overload recovery time. Common mode capacitors C7, C9 and differential capacitor C8 are used to filter the common mode and differential voltage spikes. For switching applications or where fast transients are caused by hot plugging the source or load, external protection components may be needed. The external current limiting resistor (R6) in Figure 1 will limit the peak current through the internal ESD diodes to <20mA. This condition can occur in applications that experience high levels of in-rush current causing high peak voltages February 18, 2010 AN1531.0 1 that can damage the internal ESD diodes of the ISL28005. If the current limiting resistor is required, it needs to be placed on the RS- input (R6). Placing it on the RS+ input side (R7) will result in a much larger error voltage due to the ISL28005 taking its supply current from the sense current in high-side applications. For example: Current limiting resistor R6 with a value of 100Ω will provide protection for a 2V transient with the maximum of 20mA flowing through the input while adding only an additional 13µV (worst case over-temperature) of VOS as shown in Equation 1. Note: Worst case over-temperature input bias current on the RS- input is 130nA. R 6 × I RS- = 100Ω × 130nA = 13μV (EQ. 1) Current limiting resistor R7 with value of 100Ω will provide the same transient protection, but with an error voltage of 800µV. Note: Worst case over-temperature input bias current on the RS+ input is 8µA as shown in Equation 2. R 7 × I RS+ = 100Ω × 8μA = 800μV (EQ. 2) R7 is a carry-over from our characterization board and was used to measure input bias current. The evaluation board is populated with a zero ohm resistor for R7. Power Supplies External power connections are made through the VS+ and Ground connections on the evaluation board. Capacitors C2 and C4 perform two duties, de-coupling the supplies and with R15, filtering of the power supply noise. Anti-reverse diodes D1 and D3 protect the circuit in the case of accidental polarity reversal of the supply. Resistor R12 is used to connect ground to the fixed gain parts. ISL2800XEVAL1Z and BOM Figure 3 shows the top view of the ISL2800XEVAL1Z evaluation board. The evaluation board Bill Of Materials is given in Table 1. CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2010. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1531 I-SENSE- I-SENSE+ J4 J5 C7 R7 D3 0 0 R23 0 100 R6 0.10 R18 C9 C8 0.01µF 1000pF S1AB R3 1000pF D2 OPTIONAL TRANSIENT PROTECTION DNP J13 R13 OPEN C10 R26 I-SENSE OUT 0 R9 DNP J6 0 U1 V-REF 1 J1 2 ISL28005 4 SOT23_5 0 R12 3 5 C2 1µF C4 0.01µF D1 J3 0 J2 R15 S1AB GND VS+ FIGURE 1. SIMPLIFIED ISL2800XEVAL1Z SCHEMATIC DIAGRAM 2 AN1531.0 February 18, 2010 Application Note 1531 R16-R20 AND R21-R25 ARE FOR KELVIN CONNECTIONS R1 DNP R2 I-SENSE+ 1 J5 1 DNP R3 D3 0.10 R4 S1AB I-SENSE1 J4 2 DNP R5 C8 1000pF DNP DNP R21 0 R22 DNP R23 0 DNP R24 R25 DNP R20 DNP R7 C7 100 R6 0 R19 DNP R18 DNP R17 R16 DNP C9 0.01µF 1000pF D2 DNP DNP C20 3 ISL28005 SOT23_5 OPEN OPEN C10 R26 0 2 0 R12 R14 1 2 J6 5 I-SENSE OUT 5 1 DNP DNP R11 4 C2 1µF C4 0.01µF 2 D1 1 GND 100 J3 1 R15 S1AB J2 J1 1 R10 U1 V-REF DNP R9 R8 0 DNP R13 3 4 J13 VS+ FIGURE 2. ISL2800XEVAL1Z SCHEMATIC DIAGRAM 3 AN1531.0 February 18, 2010 Application Note 1531 FIGURE 3. ISL2800XEVAL1Z TOP VIEW TABLE 1. ISL2800XEVAL1Z COMPONENTS PARTS LIST DEVICE # C2 DESCRIPTION CAP, SMD, 0805, 1µF, 50V, 20%, X7R, ROHS COMMENTS Power Supply Decoupling and Input Filter C4, C8 CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS Power Supply Decoupling/Input Filter and Differential Current Sense Filter C7, C9 CAP, SMD, 0603, 1000pF, 50V, 10%, X7R, ROHS Common Mode Current Sense Filter C10, C20 D1, D3 CAP, SMD, 0603, DNP - Place Holder, ROHS User Selectable Capacitors - Not Populated Diode-Rectifier, SMD, S1AB, 50V, ROHS Reverse Power Protection U1 (ISL28005-100EVAL1Z) ISL28005FH100Z-T7, SOT-23, ROHS U1 (ISL28005-50EVAL1Z) ISL28005FH50Z-T7, SOT-23, ROHS U1 (ISL28005-20EVAL1Z) ISL28005FH20Z-T7, SOT-23, ROHS R16, R17, R19 -R22, R24, R25 Resistor, SMD, 0603, MF, DNP - Place Holder User Selectable Kelvin Connection - Not Populated R26 Resistor, SMD, 0603, MF, DNP - Place Holder User Selectable Output Load Resistor - Not Populated Resistor, SMD, 2512, 0.1Ω, 1W, 1%, TF, ROHS Sense Resistor Resistor, SMD, 2512, DNP - Place Holder User Selectable Sense Resistors - Not Populated Resistor, SMD, 0603, 0Ω, 1/10W, TF, ROHS Zero Ohm User Selectable Resistors Resistor, SMD, 0603, 100Ω, 1/10W, TF, ROHS Current Limiting Resistors R3 R1, R2, R4, R5 R6, R7, R13, R18, R23 R15 Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 4 AN1531.0 February 18, 2010