LMV243BLEVAL

User's Guide SNWA008A – April 2008 – Revised April 2013 AN-1805 LMV243 Single-Channel, Quad-Band GSM Power Controller Evaluation Board 1 General Description This board can be used to evaluate the Texas Instruments LMV243 Single-Channel, Quad-Band GSM Power Controller. The device is intended for use within an RF transmit power control loop in GSM mobile phones and supports GaAs HBT and bipolar RF single supply power amplifiers (PA's). The key value is its immunity to changes in the PA gain control function. It contains a 50 dB logarithmic amplifier detector and interfaces directly with the directional coupler. The operating frequency range of the device is from 450 MHz to 2 GHz . 2 Basic Operation The LMV243 RF power controller provides an accurate temperature compensated DC output voltage (with a negative slope) that relates linearly to the applied RF input power in dBm. To evaluate the LMV243 in a simple straight forward way, the control loop is formed by the LMV243 and resistor R5 instead of LMV243, PA, and a directional coupler. In an actual closed loop TX control system, including a PA, resistor R5 should be removed. In an open loop measurement configuration the output voltage ramps down with increasing input power from a maximum voltage defined by VRAMP. This maximum output voltage equals VOUT = VRAMP* R5/ RRAMP, where 1/RRAMP is the transconductance defined in the datasheet. The single supply voltage ranges from 2.7V to 3.3V and can be applied through connectors P5 and P6. The input interface consists of the RF input (P1), a ramp voltage applied through P3 and a digital input TX_EN (P2) to perform the function "Shutdown/Transmit Enable." The device will be active in the case TX_EN = HI, otherwise, the device is in a low power consumption shutdown mode. During shutdown the output will be in high impedance mode (tristate). A single external RC combination is used to provide stable operations that accommodates individual PA characteristics. This is done with resistor R4 and capacitor C3. All trademarks are the property of their respective owners. SNWA008A – April 2008 – Revised April 2013 Submit Documentation Feedback AN-1805 LMV243 Single-Channel, Quad-Band GSM Power Controller Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated 1 Schematic 3 www.ti.com Schematic The schematic of the evaluation board is shown in Figure 1. VDD P4 U1 OUT P1 A3 RF IN RF IN B3 TX_EN B1 LMV243 A1 C2 C1 P2 A2 OUT COMP R4 J4 0: J3 R5 R6 C3 J2 20 k: 100 k: 68 pF C3 J1 VRAMP TX_EN R1 GND 51: P5 U1 ± pin A3 VDD P3 P6 VRAMP R2 0: R3 + C1 100 µF C2 10 nF GND U1 ± pin A2, C3 51: Figure 1. Schematic of the Evaluation Board 4 Bill of Materials The Bill of Material (BOM) of the evaluation board is listed in Table 1. Table 1. Bill of Materials of the Evaluation Board 2 Designator Description Comment C1 Case_D Capacitor 100 µF C2 0603 Capacitor 10 nF C3 0603 Capacitor 68 pF P1 Connector SMA P2, P3, P4 Connector BNC P5, P6 Connector Banana R1, R3 0603 Resistor 51Ω R2, R4 0603 Resistor 0Ω R5 Axial Resistor 20 kΩ R6 0603 Resistor 100 kΩ U1 DSBGA LMV243 AN-1805 LMV243 Single-Channel, Quad-Band GSM Power Controller Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated SNWA008A – April 2008 – Revised April 2013 Submit Documentation Feedback Layout www.ti.com 5 Layout The layout of the evaluation board is shown in Figure 2. All Layers Silk Screen Figure 2. Layout of the Evaluation Board SNWA008A – April 2008 – Revised April 2013 Submit Documentation Feedback AN-1805 LMV243 Single-Channel, Quad-Band GSM Power Controller Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated 3 Measurement Procedure 6 www.ti.com Measurement Procedure The performance of the LMV243 can be measured with the setup shown in Figure 3. In this measurement example a supply voltage of 2.8V is applied by the power supply. The LMV243 is set in active mode by connecting TX_EN (P2) to VDD, which is 2.8V. VRAMP is set to 1.4V. An RF signal is applied by the RF generator to connector P1. The RF power is swept from -70 dBm to +16 dBm. The resulting output voltage is measured with a multimeter connected to P4. VDD Power Supply VDD TX_EN P2 VRAMP P5 P3 Evaluation Board LMV243 RF IN RF Signal Generator P4 OUT Digital Volt Meter P1 P6 GND Figure 3. Measurement Setup 7 Measurement Results Figure 4 shows the output voltage and the log conformance error versus the applied RF power. The RF power is swept for three different frequencies. 3 3 VOUT, 900 MHz VOUT, 1800 MHz 2.6 2 2.2 1 1.8 0 1.4 900 MHz 1800 MHz 1900 MHz -1 ERROR (dB) VOUT (V) VOUT, 1900 MHz -2 1 20 k: BETWEEN COMP AND OUT 0.6 -70 -60 -50 -40 -30 -20 -10 0 -3 10 20 RF INPUT POWER (dBm) Figure 4. Frequency Response 4 AN-1805 LMV243 Single-Channel, Quad-Band GSM Power Controller Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated SNWA008A – April 2008 – Revised April 2013 Submit Documentation Feedback IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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