PA74A

EK21 Evaluation Kit APPLICABLE PARTS (SOLD SEPARATELY) • PA74 INTRODUCTION This easy-to-use kit provides a platform for the evaluation of the PA74 power op amp. It can be used to analyze a multitude of standard or proprietary circuit configurations. In addition, it is flexible enough to do most standard amplifier test configurations. The schematic for 1/2 of the PC board is shown in Figure 2. The schematic for the other half is identical except part reference designators are primed (i.e. R1 = R1'). Note that all of the components shown on the schematic will probably not be used for any single circuit. The component locations on the PC board (See Figure 3) provide maximum flexibility for a variety of configurations. Also included are loops for current probes as well as connection pads on the edge of the PC board for easy interconnects. The hardware required to mount the PC board and the device under evaluation to the heatsink are included in the kit. Because of the limitless combination of configurations and component values that can be used, no other parts are included in this kit. Figure 1: PCB Layout TOP SIDE C7' R8' R15' R7' C4' C3' R6' C5' R5' C2' +V' 1' EVAL02 REV. PA74 EVAL. C7 C9 C11 R8 OUT B R15 R10 R11 C13 R16 8 C14 -V R2 7 10 9 8 D2 D3 D4 J1 D1 3 OUT A R14 R13 R12 C16 R17 1 C15 4 6.00 R9 R3 R4 C6 C8 C12 6 OUT B' OUT A' C10' C1' 2' J1' R14' R13' R12' R17' C16' C15' 4' 13' D4' 1 D1' 8 3' D2' -V' 9' D3' R10' R11' C14' R16' C13' 10' R2' C9' C11' R3' R9' C6' R4' 8' R1' C8' 7' C12' 6' R7 R6 C4 R1 R5 C3 C1' C5 2 C10 +V 13 C2 1 8.00 BOTTOM SIDE www.apexanalog.com © Apex Microtechnology Inc. All rights reserved Jan 2016 EK21U Rev L EK21 Figure 2: EK Schematic 2 EK21U Rev L EK21 TYPICAL COMPONENT FUNCTIONS Component Function R1 Feedback resistor, A side R2 Input resistor, B side, bridge mode R3 Feedback resistor, B side R4 Input resistor, B side R5 Input resistor, A side R6 Input bias current measurement (Note 4) R7 Output current sense resistor or loop for current probe R8 Output current sense resistor or loop for current probe R9 Input bias current measurement (Note 4) R10 Noise gain compensation (Note 1) R11 Resistor divider network for single supply bias (Note 2) R12 Resistor divider network for single supply bias (Note 2) R13 Noise gain compensation (Note 1) R14 Input bias current measurement R15 Input bias current measurement R16 Resistor divider network for single supply bias (Note 2) R17 Resistor divider network for single supply bias (Note 2) C1 Input coupling C2 AC gain set C3 AC gain or stability (Note 1) C4 Power supply bypass C5 Power supply bypass C6 AC gain or stability (Note 1) C7 AC gain set C8 Input coupling C9 Noise gain compensation (Note 1) C10 Noise gain compensation (Note 1) C11 Power supply bypass (Note 3) C12 Power supply bypass (Note 3) D1,2,3,4 Flyback protection (Note 5) C13-16 Bias node noise bypass (Note 2) EK21U Rev L 3 EK21 PARTS LIST Reference Manufacturer Part # Description QTY HS11 Heatsink 1 EVAL02 PC Board 1 MS03 Mating Socket 2 HWRE01 Hardware Kit TW03 Thermal Washer 1 1 Box (10) HWRE01 contains the following: • 4 x #8 Panhead Screw • 4 x #6 x 1.25" Panhead Screw • 4 x #8 0.375" Hex Spacer • 4 x #6 x 5/16” Hex Nut • 4 x #8 1.00" Hex Standoff • 2 x #6 x 1/4” Hex Nut BEFORE YOU GET STARTED • • • • • • • • • All Apex Microtechnology amplifiers should be handled using proper ESD precautions! Initially set all power supplies to the minimum operating levels allowed in the device data sheet. Check for oscillations. Always use the heatsink included in this kit with thermal grease or a TW03 and torque the part to the specified 4-7 in-lbs (0.45 - 0.79 N•m). Do not change connections while the circuit is under power. Never exceed any of the absolute maximums listed in the device data sheet. Always use adequate power supply bypassing. Remember that internal power does not equal load power. Do not count on internal diodes to protect the output against sustained, high frequency, high energy kickback pulses. ASSEMBLY HINTS The mating sockets included with this kit have recessed nut sockets for mounting the device under evaluation. This allows assembly from one side of the heatsink, making it easy to swap devices under evaluation. The sizes of the stand-offs were selected to allow proper spacing of the board-to-heatsink and allow enough height for components when the assembly is inverted. ASSEMBLY 1. 2. 3. 4. 5. 6. 4 Insert a #6 x 5/16” hex nut in each of the nut socket recesses located on the bottom of the mating socket. Insert the socket into the pc board until it is firmly pressed against the ground plane side of the pc board. Solder the socket in place (see Figure 3). Be sure the nuts are in the recesses prior to soldering. Solder all passive components from the DUT side. Mount the PC board assembly to the heatsink using the stand-offs and spacers included. Apply thermal grease or a TW03 to the bottom of the device under evaluation. Insert into the mating socket through the heatsink. EK21U Rev L EK21 7. Use the #6 x 1.25" panhead screws to mount the amplifier to the heat sink. Do not overtorque. Recommended mounting torque is 4-7 in-lbs (0.45 - 0.79 N•m). Mounting precautions, general operating considerations, and heatsinking information may be found in the Apex Microtechnology‘s AN01 Application Note 1. Note: Refer to HS11 Heatsink in Accessories Section Figure 3: Assembly Diagram Heatsink Power Op Amp Package #6 Screw #8 Screw #8 .375" Hex Spacer Recessed Nuts Teflon Tubing (2 Opposite Pins Minimum) PC Board #8 1.00" Hex Standoff Mating Socket BRIDGE MODE OPERATION There are two types of bridge mode operation that will be covered in this section; dual (or split) supply and single supply. The PA74 is well suited for both types of bridge mode operation. If another vendor’s pin compatible part is to be compared to the PA74, a close look at output swing and input common mode range is in order. The features that make the PA74 an excellent choice for bridge operation are not included in most other amplifiers. A lack of common mode range may cause permanent damage to other pin compatible parts and the inability of other amplifiers to swing close to the supply rails may cause a lack of available output voltage at the load as well as increase internal dissipation. The circuit shown in Figure 4 is a dual supply bridge using the “master-slave” configuration. Resistors R 6,7,8,9,14,15 and J1 should be shorts. The available output voltage swing is Vss–(2*Vsat). If operating a PA74A at 3 Amps and 30 Volts total supply this translates to: V AB  max  = 30 –  2  3.5  = 23 Of course this 23 volts may be applied in either direction across the load. To set the gain of the circuit you must determine the desired voltage across the load at Vin = full scale. Inserting these values into the following equation will yield the ratio of R1 to R5. V AB  R1  ------------------------  2  V in  = R5 The values of R 1,2,3, and 5 should be chosen such that input bias current will not cause an error voltage that is unacceptable. Set R2 equal to R3 to configure the slave amplifier as a unity gain inverter. Figure 5 shows a typical single supply bridge circuit for an AC coupled input signal. DC coupled inputs may require a different topology to accommodate proper gain and offset terms for a desired transfer function. EK21U Rev L 5 EK21 The gain and output voltage capability for the single supply bridge are determined the same way as the dual supply bridge (see AN#2). The difference is the bias requirement for the slave amplifier. The noninverting input of the slave amplifier should be biased at mid supply, and must be bypassed. Figure 4: Dual Supply Bridge Figure 5: Single Supply Bridge HS11 HEATSINK NOTE The HS11 Heatsink is provided in this evaluation kit to guarantee adequate thermal design through heat removal from the part under evaluation. Once maximum power dissipation for the application is determined (refer to “General Operating Considerations” and Application Note 11 in the Apex Microtechnology DATA BOOK), the final mechanical design will probably require substantially less heatsinking. Apex Microtechnology makes no representation that the use or interconnection of the circuits described herein will not infringe on existing or future patent rights, nor do the descriptions contained herein imply the granting of licenses to make, use or sell equipment constructed in accordance therewith. 6 EK21U Rev L EK21 Notes: Refer to the following sections of the Apex Microtechnology’ Application Note Library as noted. 1. See Stability section of “General Operating Considerations.” 2. See “Gen. Operating Considerations,” and AN03 “Bridge Circuit Drives.” 3. See Power Supplies section of “General Operating Considerations.” 4. See “Parameter Definitions and Test Methods.” 5. See Amplifier Protection section of “Gen. Operating Considerations.” NEED TECHNICAL HELP? CONTACT APEX SUPPORT! For all Apex Microtechnology product questions and inquiries, call toll free 800-546-2739 in North America. For inquiries via email, please contact apex.support@apexanalog.com. International customers can also request support by contacting their local Apex Microtechnology Sales Representative. To find the one nearest to you, go to www.apexanalog.com IMPORTANT NOTICE Apex Microtechnology, Inc. has made every effort to insure the accuracy of the content contained in this document. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (expressed or implied). Apex Microtechnology reserves the right to make changes without further notice to any specifications or products mentioned herein to improve reliability. This document is the property of Apex Microtechnology and by furnishing this information, Apex Microtechnology grants no license, expressed or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. Apex Microtechnology owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Apex Microtechnology integrated circuits or other products of Apex Microtechnology. This consent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale. APEX MICROTECHNOLOGY PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN PRODUCTS USED FOR LIFE SUPPORT, AUTOMOTIVE SAFETY, SECURITY DEVICES, OR OTHER CRITICAL APPLICATIONS. PRODUCTS IN SUCH APPLICATIONS ARE UNDERSTOOD TO BE FULLY AT THE CUSTOMER OR THE CUSTOMER’S RISK. Apex Microtechnology, Apex and Apex Precision Power are trademarks of Apex Microtechnology, Inc. All other corporate names noted herein may be trademarks of their respective holders. EK21U Rev L 7