DEMO MANUAL DC2027A LTC4364HDE-1, 2 12V Surge Stopper with Ideal Diode Description Demonstration circuit 2027A showcases the LTC 4364 waveform 5A. Sustained overvoltage or overcurrent condi- surge stopper with ideal diode in a 12V, 1A application. tions cause the LTC4364 to turn off after a timer delay. DC inputs of up to 80V and transients to 250V are limited The LTC4364-1 (DC2027A-A) latches off and is reset to just 28.7V at the output. Sagging and reverse-polarity by pulling SHDN low for at least 100s. The LTC4364-2 inputs of up to 24V are isolated from the output by a (DC2027A-B) automatically retries after a three minute reverse-blocking MOSFET configured as an ideal diode. cool down delay. Start-up and retry are inhibited in the Further, the output is protected against backfeeding. The presence of an input overvoltage. output may be driven 20V to +30V without circuit damage Design files for this circuit board are available at or backfeeding into the input. DEMO MANUAL DC2027A Quick tart sDp OPERATION While a maximum load current of 1A is permitted during start-up and overvoltage conditions, current limit is set DC2027A has been designed for 12V operation with a load to 2.5A. This higher current level is permissible during of up to 1A. M1 limits surges, spikes and transients, such normal (12V) operation. In short-circuit conditions where as are commonly encountered in automotive applications. V = 0V, current limit folds back to 1.25A. OUT For positive-going events, the output is regulated at 28.7V. Spikes of up to 250V are permissible for 1ms, limited by The output is protected against backfeeding over a range the pulse capability of R4. The load may continue operating of 20V to 30V. If the output is connected to a low imped- during positive transients, including load dump, without ance source of less voltage than the input, M1 will likely interruption. go into current limit and fault off. If the output is higher than the input, M2 will block backfeeding. In the case that Reverse inputs of up to 24V are blocked from reaching DC the output is higher than the 28.7V regulation voltage, the the load by M2. Beyond 24V, a 400W transient voltage timer will run and M1 will fault off. suppressor, D4, clamps the input. Consult the SMAJ24A data sheet for specific information about peak current and Optional Components time duration for spikes exceeding 24V. The pulse power limitations of R4 may be avoided by DC2027A-A is fitted with the LTC4364-1. This device adding Q1. Pads are located on the bottom of the board. latches off after a sustained overcurrent or overvoltage Remove RVCC (a 0 jumper) and increase R4 to 270k fault. Operation is resumed after cycling the supply, or (see Figure 1). Remember that the board spacing is only after pulsing SHDN low for at least 100s. 78mils, and that this is inadequate for creepage and clear- DC2027A-B is fitted with the LTC4364-2, which also shuts ance at 250V . DC off the output in the presence of a sustained fault condi- Pads are included on the bottom of the board for optional tion, but automatically retries after a cool-down delay of output capacitors COUT3 and COUT4, in the event additional 180 seconds. The cool-down delay may be prematurely bypassing is desired. interrupted by pulsing SHDN low for at least 100s. Through-hole pads are included for adapting DC2027A to In both cases, retry is inhibited by the OV pin if the input an off-board power stage, as shown in Figure 2. is higher than 16.8V, as is start-up. INPUT D4 SMAJ24A R4 270k 1206 D3 ES1G Q1 PZTA42 LTC4364 RVCC REMOVED V CC C1 D1 100nF CMZ5945B dc2027a F01 100V 68V Figure 1. Remove RVCC and Add Q1 to Withstand Prolonged Inputs of Up to 250V. R4 Is Increased to 270k dc2027af 2 ure roce