QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 563 SINGLE AND DUAL MARGINING CONTROLLER LTC2920-1CS5 LTC2920-2CMS8 DESCRIPTION Demonstration circuit 563 contains two separate cir- capacitor, and pads for external connections. There cuits: a (single channel) LTC2920-1 and a (dual chan- are also component locations for adding 0805 resis- nel) LTC2920-2 Power Supply Margining Controllers. tors. These resistors are specific to each applica- This board is meant to be connected to up to three tion and must be installed to demonstrate Voltage power supplies and demonstrates the voltage margin- Margining. ing capabilities of the LTC2920. The board is scribed Design files for this circuit board are available. Call for easy separation of the two circuits if desired. the LTC factory. Each circuit contains a Margining Controller, bypass QUICK START PROCEDURE Referring to Figure 1, the Vcc1 and Gnd1 pins provide are two positions for each of the two Rset resistors. the power and ground connections for the LTC2920-1 The R1L and R2L positions are similar to the (single). The Vcc2 and Gnd2 pins provide the power RLOW position described above. The R1H and and ground connections for the LTC2920-2 (dual). R2H positions are similar to the RHI position de- The Vcc voltage can generally be varied between 2.2V scribed above. and 6.0V. Vcc must be at least 0.6 volts higher than the voltage at the Im pin. See the LTC2920 Data The In pins can be connected to a system controller Sheet for other design considerations on minimum that has a 3-state output, or manually connected as Vcc voltage and Vcc filtering. Be sure to connect the shown. When using a 3-state output to control the In ground pin(s) to the same ground as the power sup- pin, placing the (3-state) output in the high-Z state ply(s) being margined. will float the In pin, and cause the controlled Im pin to be in a high impedance state. Raising an In pin For margining power supplies with external feedback above 2.0 Volts will cause its respective Im pin to resistors, the Im pins should be connected to the sink current. Lowering an In pin below 0.6 Volts will power supply feedback node. For margining power cause its respective Im pin to source current. See the supplies using trim pins, the Im pin should be con- LTC2920 Data Sheet for details. The In pins may also nected to the power supply trim pin. be controlled manually by connecting them to Vcc, ground, or left floating. The Imargin current sourced or sunk from each Im pin is individually programmed by its respective on After calculating and inserting the Rset resistor(s) as board Rset resistor. For the LTC2920-1 circuit, there described above, place the DC563 board as close as are two possible locations for the Rset resistor. Plac- possible to the power supplie(s) being margined. The ing the Rset resistor in the RLOW position will pro- ground, Vcc, and Im pins should be connected with gram the Imargin current at 1V / Rset. Placing the the shortest practical wires. Rset resistor in the RHI position will program the Imargin current at 30 * 1V / Rset. See the LTC2920 With power applied, the power supply output(s) Data Sheet for the specification limits of the high and should be at their nominal values with the In pin(s) low current ranges. On the LTC2920-2 circuit, there 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 563 SINGLE AND DUAL MARGINING CONTROLLER floating. Raising the In pin(s) above 2.0 V will cause If the LTC2920 Vcc pin is connected to power sup- the power supply output voltage to increase by the plies that are compensated to be only marginally sta- desired margin voltage. Lowering the In pin(s) below ble, oscillations may be observed. If oscillations are 0.6 V will cause the power supply output voltage to observed while margining a power supply, connect decrease by the desired margin voltage. When con- the Vcc pin to the power supply using an axial lead nected to trim pins on DC to DC modules, the po- resistor instead of a wire. See the LTC2920 Data larity of the voltage margining may be inverted. Sheet for calculating the value of this resistor. Figure 1. Proper Measurement Equipment Setup 2