DEMO MANUAL DC1018B-B LTC4356-2 Overvoltage Protection Regulator FEATURES DESCRIPTION n For Automotive Applications up to 3A Demonstration Circuit DC1018B-B showcases the n Triple Layout for D-Pak, D2-Pak or S-8 MOSFETs LT4356-2 Surge Stopper in a 12V, 3A application. Input n 0.093-inch Turret Holes Accommodate 12 AWG Wire transients of up to 60V are limited to 16V at the output n LEDs Show Input, Outputs, Fault and Enable sustained overvoltage conditions cause the limiter to trip n Easily Modified for up to 20A off and retry after the overvoltage is removed. LEDs indicate the presence of +12V input and output, as well as state of the fault output, FLT and enable output, EN. APPLICATIONS Input and output connections are made by 93 mil turrets n Servers, Routers, Switches which if removed, accommodate insertion of up to 12 n Mass Storage gauge wires for in-situ testing. n Fan Trays Design files for this circuit board are available. n Automotive Modules All registered trademarks and trademarks are the property of their respective owners. PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Input Operating Range 4 12 60 V IN Peak Input Voltage Clipped by Transient Voltage Suppressor 100 V V Output Limiting Voltage 15.3 16 16.7 V LIMIT I Maximum Load Current 3.5 A OUT Rev. 0 1DEMO MANUAL DC1018B-B QUICK START PROCEDURE Board Layout At higher currents the clamp DCL must be proportionately increased. This catches the locally generated spike at the DC1018B-B is a 4-layer board. There are planes for input, MOSFET drain when the output goes into regulation. The output, drain and ground these are replicated on each layer. energy content of this spike is a direct function of input The spare amplifier is kept active during shutdown in the slew rate and output load capacitance. LT4356CDE-2, resulting in a supply current of about 50A. Changing Output Regulation Level The 93 mil input and output connection turrets are not swaged and may be removed for attachment of up to 12 The output limiting or regulation voltage is easily modified gauge wire. Banana jacks facilitate bench testing. by simply changing R1 and R2 to values appropriate for the application. The FB pin servo voltage is 1.25V. See the Sufficient copper is available to support applications of data sheet for a full description of this pin and equations. at least 20A. As built, the demo board clamps at 16V. LEDs are included as quick debug indicators. These LEDs The actual operating voltage is independent of the clamp- show: ing volt-age, and may be anything from the minimum LED1 12V input Green operating voltage of 4V up to the clamping voltage. Thus while the demo board is labeled 12V, it can operate with LED3 12V output Green any other sub-16V input such as a 5V regulated supply, a LED4 FLT Red 6V gelcell, or a stack of 8 NiMH cells, or a 9V impedance limited wall cube, to name but a few possible inputs. LED5 EN Green The enable and fault LEDs are both powered in such a Supply Current way that the signals present on their associated turrets The low shutdown current of the LT4356-2 is impossible are limited in voltage (see schematic). To this end a simple to measure on the demo board because of the presence series regulator (Q2 and D6) has been included on the of the input LED, LED1, and the LED Supply. Remove R10 demo board for powering the FLT output the FLT pin and R17 to eliminate these paths. itself is rated to 80V. Note that above 16V, D4 will draw current. Below 16V R8 is an optional pull-up resistor for the SHDN pin. leakage in D4, Q2s collector-base junction in series with D6 and Q1 will add to the LT4356-2s supply current. Modifying Current Limit These effects are insignificant at room temperature. DC1018B-B is designed for 3.5A maximum load current and may be modified for higher or lower current levels. Small Turrets Sense resistor RSNS1-3 pads are designed for 1206 or No connection to any of the small turrets is necessary 2010 sense resistors. The LT4356-2 current sense voltage to make the board operatethe LT4356-2 defaults to the is 50mV, with limiting occurring at 50mV/RSNS. Optional ON state. footprints for D2-pak or S-8 MOSFETs allow for much higher or lower current levels. Sufficient copper is present SHDN is pulled high internally. If this turret is left open, to handle in excess of 20A. If the S-8 footprint is used, the board will turn on when power is applied. Short this move R3 (10 ohms) to the bottom of the board, R3B. This turret to ground to turn off the LT4356-2. is the gate resistor for the S-8 MOSFET. Rev. 0 2