QUICKD DEMO CIRCUIT 1531 QUICK START GUIDE LT3092EDD Two-Terminal Current Source DESCRIPTION Demonstration circuit 1531A is a two-terminal current source featuring LT®3092. It requires only two resistors to set an output current between 0.5mA and 200mA. It is stable without input and output capacitors, offering high DC and AC impedance. It can be used in many applications such as 2-terminal floating current source, GND referred current source, variable current source, in-line limiter and intrinsic safety circuits. A key feature of the LT3092 is the capability to supply a wide output current range. By using two external resistors, the output current can be programmed to any level between 0.5mA and 200mA, while the input-to-output difference voltage is limited to 40V and the power dissipation is limited below the thermal limit. Internal protection circuitry includes reverse-battery and reverse-current protection, current limiting and thermal limiting. LT3092 regulator is offered in the thermally enhanced 8-lead TSOT-23, 3-lead SOT-223 and 8-lead 3mm× 3mm DFN packages. The LT3092 datasheet gives a complete description of the part, operation and application information. The datasheet should be read in conjunction with this quick start guide for working on or modifying the demo circuit 1531A. Design files for this circuit board are available. Call the LTC factory. , LTC, LTM, LT and uModule are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Table 1. Performance Summary ( TA = 25oC ) PARAMETER CONDITION VALUE Minimum Vin-Vout Voltage IOUT=1mA 1.2V Maximum Vin-Vout Voltage Output Current 40V JP1, IOUT=200mA 200mA ±3% JP1, IOUT=100mA 100mA ±3% JP1, IOUT=50mA 50mA ±3% JP1, IOUT=ADJ 0.5mA~110mA 1 QUICKD DEMO CIRCUIT 1531 QUICK START GUIDE QUICK START PROCEDURE The DC1531A is easy to set up to evaluate the performance of the LT3092. Refer to Figure 1. for proper measurement equipment setup and following the procedures below: 1. Before proceeding to test, use jumper JP1 for the desired output current (200mA, 100mA or 50mA). If the output current is different from the above values, use the ADJ option. 2. Assume 200mA is the desired output. Apply 2V across VIN (to VOUT). The measured IOUT should be 200mA ± 3% (195mA to 207mA). 3. Vary Vin-Vout from 2V to 40V. IOUT should measure 200mA ± 3% (195mA to 207mA). Note: Minimum Vin-Vout depends on IOUT. datasheet for dropout curves. See Figure 1. Proper Measurement Equipment Setup 2 QUICKD DEMO CIRCUIT 1531 QUICK START GUIDE ADDITIONAL NOTE Although the LT3092’s design strives to be stable without any capacitors over a wide variety of operating conditions, it is not possible to test for all possible combinations of input and output impedances that the LT3092 will encounter. These impedances may include resistive, capacitive and inductive components and may be complex distributed networks. In addition, the current source’s value will differ between applications and its connection may be GND referenced, power supply referenced or floating in a signal line path. Linear Technology strongly recommends that stability be tested in circuits for any LT3092 application. When operating with a capacitor across the SET pin resistor, external compensation is usually required to maintain stability and compensate for the introduced pole. Optional input capacitor, output capacitor or RC compensation can be installed on the back side of the DC1531A if necessary. See datasheet for details. 3 QUICKD DEMO CIRCUIT 1531 QUICK START GUIDE 4