QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 925 TRIPLE OUTPUT TFT LCD BIAS SUPPLY LT3489EMS8E DESCRIPTION Demonstration circuit 925 features the LT3489EMS8E in a circuit specifically designed to drive large TFT/LCD displays. The demo circuit demonstrates small size and low component count in a Boost Circuit. It converts a 3.3V-6V input to 8V at 600mA, 23V at 10mA and -8V at 20mA. Since the maximum Vin of the LT3489 is 16V, this Demo circuit will work well at higher inputs. The only limitation is that the input has to be lower than the Boost converter output (8V) in order to stay in regulation. This circuit is designed to demonstrate the capacitor programmable Soft-Start feature, advantages of the 2MHz constant switching frequency and the internal 2.5A, 40V switch. This circuit is intended for large TFT-LCD displays and other space-conscious applications such as Bias Supplies, GPS Receivers, DSL Modems and Local Power Supplies. Design files for this circuit board are available. Call the LTC factory. LT is a trademark of Linear Technology Corporation Table 1. Performance Summary (TA = 25°C) PARAMETERS FOR 15V BOOST CIRCUIT CONDITION VALUE Minimum Input Voltage 3.3V Output Voltage VOUT VIN = 3.3V, IOUT = 0mA to 600mA 8V ±3% Maximum Output Current for 8V Output Vin = 3.3V, 23V@10mA and -8V@20mA 600mA Typical Output Ripple VOUT for 8V Output VIN = 3.3V , IOUT = 600mA 30mVP–P Typical Efficiency All Outputs Loaded VIN = 3.3V, Vout = 8V@400mA, -8V@20mA, 23V@10mA 83% QUICK START PROCEDURE Demonstration circuit 925 is easy to set up to evaluate the performance of the LT3489EMS8E. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. 1. Place jumpers in the following positions: JP1 On 2. With power off, connect the input power supply to Vin and GND. 3. Turn on the power at the input. 4. Check for the proper output voltages. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 5. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 925 TRIPLE OUTPUT TFT LCD BIAS SUPPLY Figure 1. Proper Measurement Equipment Setup GND VIN Figure 2. Measuring Input or Output Ripple 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 925 TRIPLE OUTPUT TFT LCD BIAS SUPPLY 3