DEMO MANUAL DC2229A DC2229A-A: LTC3877 DC2229A-B: LTC3877/LTC3874 High Current Step-Down Converter Description Demonstration circuits 2229A-A and 2229A-B feature the Additional features of this demo board include: LTC 3877 in two high output current, high efficiency, VID n Remote sensing programmed step-down converters with sub-m DCR n PLLIN and CLKOUT pins sensing. For both converters, the input voltage range is 6V to 14V and the switching frequency is 400kHz. n PGOOD, RUN and TK/SS pins The DC2229A-A provides two outputs. V is VID OUT1 n Optional resistors to tie two or more phases together programmable from 0.6V to 1.23V and V is set for OUT2 n Optional footprints for BSG0811 dual channel MOSFETs 1.5V. Both rails have a maximum load current of 30A. The DC2229A-B assembly is a four phase converter providing n Optional NTC network on the ITEMP pin of the LTC3877 a VID programmable output of 0.6V to 1.23V with a maxi- for less current limit variation over temperature mum load current of 120A. Phases 1 and 2 are controlled n Dynamic load circuit by the LTC3877 and phases 3 and 4 are controlled by the LTC3874 slave controller. The demo board uses a high density, two-sided drop-in layout. The core components for each dual phase section The demo board uses 0.25H inductors with a DCR value of consists of MOSFETs, inductors, ceramic C , ceramic IN 0.325m. The LTC3877 and LTC3874 employ a proprietary C on the top layer and the control circuit on the bottom, OUT sub-m DCR sensing architecture which enhances the resides in a 1.3 x 1.3 area of the board. signal to provide accurate control of the inductor current. The low DCR inductors, along with the use of low Q /low The LTC3877 and LTC3874 data sheets provide a complete g R discrete FETs and strong gate drivers provides description of the IC operation and application informa- DS(ON) high efficiency for high output current supplies. The full tion. These data sheets must be read in conjunction with load efficiency is 90.3%, as seen on the 1.5V rail of the the quick start guide. LTC3877 dual output converter (DC2229A-A assembly) Design files for this circuit board are available at with an input voltage of 12V. DEMO MANUAL DC2229A p s Table 1. DC2229A-A Performance Summary (T = 25C), No Airflow A PARAMETER CONDITIONS VALUES Minimum Input Voltage 6V Maximum Input Voltage 14V Output Voltage V , VID programmed I = 0A to 30A, V = 6V to 14V OUT1 OUT1 IN VID0VID5 = L 0.6V 1% VID0, VID5 = L, VID1VID4 = H 0.9V 1% VID0VID5 = H 1.23V 1% Output Voltage V I = 0A to 30A, V = 6V to 14V 1.5V 1.5% OUT2 OUT2 IN V Maximum Output Current, I V = 6V to 14V 30A OUT1 OUT1 IN V Maximum Output Current, I V = 6V to 14V 30A OUT2 OUT2 IN Nominal Switching Frequency 400kHz Efficiency V = 1.2V, I = 30A, V = 12V 89.1% typical OUT1 OUT1 IN See Figures 3 to 5 V = 1.5V, I = 30A, V = 12V 90.3% typical OUT2 OUT2 IN Table 2. DC2229A-B Performance Summary (T = 25C), No Airflow A PARAMETER CONDITIONS VALUES Minimum Input Voltage 6V Maximum Input Voltage 14V Output Voltage V , VID programmed I = 0A to 120A, V = 6V to 14V OUT OUT1 IN VID0VID5 = L 0.6V 1% VID0, VID5 = L, VID1VID4 = H 0.9V 1% VID0VID5 = H 1.23V 1% V Maximum Output Current, I V = 6V to 14V 120A OUT OUT IN Nominal Switching Frequency 400kHz Efficiency, See Figure 6 V = 1.2V, I = 120A, V = 12V 88.8% typical OUT OUT1 IN dc2229af 2 ummary erformance