THS4221EVM THS4225EVM User’s Guide April 2003 High Performance Linear Products SLOU160
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.
EVM IMPORTANT NOTICE Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not considered by TI to be fit for commercial use.
EVM WARNINGS AND RESTRICTIONS It is important to operate this EVM within the specified input and output ranges described in the EVM User’s Guide. Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM. If there are questions concerning the input range, please contact a TI field representative prior to connecting the input power.
Information About Cautions and Warnings Preface About This Manual This user’s guide describes the evaluation module (EVM) used to evaluate the THS4221 and THS4225 high-speed op amps, and includes a complete circuit description, schematics for devices under test, and bill of materials.
Trademarks The information in a caution or a warning is provided for your protection. Please read each caution and warning carefully. Related Documentation From Texas Instruments The URLs below are correct as of the date of publication of this manual. Texas Instruments applications apologizes if they change over time. J THS4221, THS4225 data sheet (SLOS399) J Application report, PowerPAD Thermally Enhanced Package (SLMA002) http://www−s.ti.com/sc/psheets/slma004/slma002.
Contents 1 Introduction and Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.1 Evaluation Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 2 Using the THS4221 and THS4225 EVMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 3 THS4221 and THS4225 EVM Applications . . . . . . . . . . . . . . . . . . . . . . .
Contents viii
Chapter 1 These EVMs provide platforms for testing the THS4221 in the 5-pin SOT (DBV) package and the THS4225 in the 8-pin MSOP (DGN) package. They contain the high-speed op amp, a number of passive components, and various features and footprints that enable the user to experiment, test, and verify various operational amplifier circuit implementations. Topic 1.1 Page Evaluation Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Evaluation Schematics 1.1 Evaluation Schematics As delivered, the EVM has a fully functional example circuit; just add power supplies, a signal source, and monitoring instrument. See Figure 1−1 and Figure 1−2 for the default schematic diagrams. The user can change the gain by changing the ratios of the feedback and gain resistors (see the device data sheet for recommended resistor values).
Evaluation Schematics Figure 1−1. Schematic of the THS4221EVM R4 1.3 kΩ +VS R2 1.3 kΩ J1 IN − U1 THS4221 1 6 Î R3 52.3 Ω 4 − 3 −VS J2 IN+ J5 −VS J4 VOUT + 2 R3 649 Ω R5 935 Ω J3 † PD 5 Î J6 GND C1 R6 † † TP1 J7 +VS FB1 FB2 + C2 100 pF C3 0.1 µF + C4 22 µF C5 22 µF C6 0.1 µF C7 100 pF † Does not apply to the THS4221EVM Figure 1−2. Schematic of the THS4225EVM J9 PD R5 1.3 kΩ C8 † +VS 7 R3 1.3 kΩ J1 IN − 2 8 − 3 U1 THS4225 6 R6 953 Ω J4 VOUT + R2 52.
1-4
Chapter 2 !" This chapter shows how to connect the THS4221 and THS4225 EVMs to test equipment. It is recommended that the user connect the EVMs as shown in this chapter to avoid damage to the EVM or the devices installed on the board. Figure 2.1 shows how to connect power supplies, 50-Ω signal source, and 50-Ω monitoring instrument to a THS4221 EVM. Figure 2.2 shows how to connect power supplies, 50-Ω signal source, and 50-Ω monitoring instrument to a THS4225EVM. Figure 2−1.
Figure 2−2. THS4225EVM Connection Diagram Figure 2−1 and Figure 2−2 show the connections to measure the output while a signal is inserted into the noninverting input of the EVM.
Chapter 3 !" # Example applications are presented in this chapter. These applications demonstrate the most popular circuits to the user, but many other circuits can be constructed. The user is encouraged to experiment with different circuits, exploring new and creative design techniques. That is the function of an evaluation board.
Inverting Video Gain Stage 3.1 Inverting Video Gain Stage The circuit described in this section is an inverting gain stage with a voltage divider on the output, shown in Figure 3−1. The voltage gain from J1 to J4 is simplified in equation 1. Assuming a 75-Ω source impedance, equation 1 indicates the gain when R1 is changed to 78.7 Ω, and R3 and R5 are changed to 75 Ω. Rt is the termination resistance of the measurement device. ǒ Ǔ + * 0.
Noninverting Video Gain Stage 3.2 Noninverting Video Gain Stage For a noninverting video gain stage, the EVM can be modified by replacing R1 with a 0 Ω resistor. A 75-Ω termination resistor is used in location R3 as shown in Figure 3−2. Equation 2 indicates the voltage gain from J2 to J4 when connected to a 75-Ω measurement instrument. VOUT + IN ) ǒ1 ) R4 Ǔǒ Rt Ǔ R2 Rt ) R5 (2) + 1 Figure 3−2. Noninverting Video Gain Stage R4 1.3 kΩ +VS 6 R2 1.
Power-Down Functionality Saves Power 3.3 Power-Down Functionality Saves Power The THS4225 EVM features a power-down pin (PD) which lowers the quiescent current from 14 mA down to 700 µA, ideal for reducing system power. The power-down pin of the amplifier defaults to the positive supply voltage in the absence of an applied voltage, putting the amplifier in the power-on mode of operation. To turn off the amplifier and conserve power, the power-down pin can be driven towards the negative rail.
Power-Down Reference Pin Operation 3.4 Power-Down Reference Pin Operation In addition to the power-down pin, the THS4225 EVM features a reference pin (REF) which allows the user to control the enable or disable power-down voltage levels applied to the PD pin. Operation of the reference pin as it relates to the power-down pin is described below. In most split-supply applications, the reference pin is connected to ground. In some cases, the user may want to connect it to the negative or positive supply rail.
Power-Down Reference Pin Operation Power-Down Threshold Voltage Levels (REF > Midrail) Supply Voltage (V) Reference Pin Voltage (V) Enable Level (V) Disable Level (V) Floating or 5 ≥4 ≤3.5 2.5 ≥0.5 ≤1 1 ≥0 ≤−0.5 Floating or 5 ≥4 ≤3.5 4 ≥3 ≤2.5 3.5 ≥2.5 ≤2 Floating or 3.3 ≥2.7 ≤1.8 ±5 5 3.3 In the above table, the threshold levels are derived by the following equations: REF − 1 V for enable REF − 1.
Chapter 4 !" $ This chapter describes the EVM hardware. It includes the EVM parts list, component placement diagram and printed circuit board layout. Table 4−1. THS4221EVM Bill of Materials Item Description SMD Size Ref. Des. PCB Qty. Manufacturer’s Part No. Distributor’s Part No.
Figure 4−1.
Table 4−2. THS4225EVM Bill of Materials Item Description SMD Size Ref. Des. PCB Qty. Manufacturer’s Part No. Distributor’s Part No. FB1, FB2 2 (Steward) HI1206N800R-00 (Digi−Key) 240-1010-1-ND 1 Bead, ferrite, 3A, 80 Ω 2 CAP, 22 µF, tantalum, 25V, 10% D C1, C2 2 (AVX) TAJD226K025R (Garrett) TAJD226K025R 3 Cap, 100 pF, ceramic, 5%, 150 V AQ12 C4, C5 2 (AVX) AQ12EM101JAJME (TTI) AQ12EM101JAJME 4 CAP, 0.
Figure 4−2.
