DEMONSTRATION CIRCUIT 1515 QUICK START GUIDE LT3050 100mA, LOW NOISE LINEAR REGULATOR WITH PRECISION CURRENT LIMIT AND DIAGNOSTIC FUNCTIONS DESCRIPTION Demonstration circuit 1515 is an adjustable 100mA ® linear regulator featuring LT 3050. LT3050 is a micropower, low noise and low dropout voltage linear regulator. The device supplies 100mA of output current with a dropout voltage of 340mV. A 10nF bypass capacitor reduces output noise to 30µVRMS in a 10Hz to 100kHz bandwidth and soft-starts the reference. The LT3050’s 45V input voltage rating combined with its precision current limit and diagnostic functions make the IC an ideal choice for robust, high reliability applications. The internal current limit should be considered when input-to-output differential is high. See the datasheet for details. if the LT3050 is in current limit, operating below its minimum output current (open-circuit) or is in thermal shutdown. LT3050 optimizes the stability and transient response with low ESR ceramic cap, requiring a minimum of 2.2µF. LT3050 current limit can be programmed by a single resistor, accurate to ±5% over a wide input voltage and temperature range. A single resistor programs the LT3050’s minimum output current monitor, useful for detecting open-circuit conditions. The current th monitor function sources a current equal to 1/100 of output current. See the datasheet “Operation” section for detailed calculation. A logic FAULT pin asserts low Design files for this circuit board are available. Call the LTC factory. Table 1. The LT3050 is available in the thermally-enhanced 12Lead 3mm×2mm DFN and MSOP packages. The LT3050 datasheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1515. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Performance Summary (TA = 25oC) PARAMETER CONDITION VALUE Minimum Input Voltage VOUT=5V, IOUT = 100mA 5.4V Maximum Input Voltage VOUT=5V, IOUT = 90mA 45V Output Voltage VOUT Header in JP6 4.99V ±2.8% Maximum Output Current VIN=12V, VOUT=5V, RIMAX=1.15k 100mA Minimum Output Current VIN=12V, VOUT=5V, RIMAX=11.3k 10mA To µP ADC Voltage VIN=12V, VOUT=5V, RIMON=3.01k, IOUT=100mA 2.98V 1 DEMONSTRATION CIRCUIT 1515 QUICK START GUIDE QUICK START PROCEDURE Demonstration circuit 1515 is easy to set up to evaluate the performance of the LT3050. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: Make sure that the input voltage does not ex- ceed 45V. protect against some, but not all, input transients due to hot-plugging with a power supply. See Application Note 88 for more details. NOTE: Connect the power supply (with power off), load, and meters as shown in Figure 1. jumper JP8 shunt is required to be placed in the OFF or ON position for proper operation. After all connections are made, turn on input power and verify that the output voltage according to the output voltage selection jumper (JP1JP7). NOTE: Place NOTE: If 1. NOTE: The shutdown the output voltage selection jumper JP1-JP7 at the desired position. not hot-plug the input voltage terminal VIN. The absolute maximum voltage on VIN is 50V and hot-plugging a power supply through wire leads to the demonstration circuit can cause the voltage on the extremely low-ESR ceramic input capacitor to ring to twice its DC value. In order to protect the IC, a higher ESR Aluminum Electrolytic capacitor is placed at the input terminals. This may the output voltage is too low, temporarily disconnect the load to make sure that the load is not set too high. NOTE: Do 2. Once the proper output voltages are established, adjust the load within the operating range and observe the output voltage regulation, efficiency and other parameters. 2 DEMONSTRATION CIRCUIT 1515 QUICK START GUIDE Figure 1. Proper Measurement Equipment Setup 3 DEMONSTRATION CIRCUIT 1515 QUICK START GUIDE 4