LTC2923 Power Supply Tracking Controller Fea T Descrip T n Flexible Power Supply Tracking The LTC 2923 provides a simple solution to power supply n Tracks Both Up and Down tracking and sequencing requirements. By selecting a few n Power Supply Sequencing resistors, the supplies can be configured to ramp-up and n Supply Stability is Not Affected ramp-down together or with voltage offsets, time delays n Controls Two Supplies Without Series FETs or different ramp rates. n Controls a Third Supply With a Series FET By introducing currents into the feedback nodes of two n Adjustable Ramp Rates independent switching regulators, the LTC2923 causes n Electronic Circuit Breaker their outputs to track without inserting any pass element n Available in 10-Lead MS and 12-Lead losses. Because the currents are controlled in an open- (4mm 3mm) DFN Packages loop manner, the LTC2923 does not affect the transient response or stability of the supplies. Furthermore, it a T presents a high impedance when power-up is complete, n V and V Supply Tracking effectively removing it from the DC/DC circuit. CORE I/O n Microprocessor, DSP and FPGA Supplies For systems that require a third supply, one supply can n Servers be controlled with a series FET. This optional series FET n Communication Systems can also control a supply that does not allow direct ac- L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear cess to its feedback resistors (e.g., a power module) or Technology Corporation. All other trademarks are the property of their respective owners. Patents Pending. a supply whose output cannot be forced to ground (e.g., a 3-terminal linear regulator). When the FET is used, an electronic circuit breaker provides protection from short- circuit conditions. Typical a T Q1 V IN 3.3V 3.3V 3.3V 2.5V 1V/DIV 1.8V 10nF V IN IN 138k V RAMP GATE CC DC/DC 2923 TA02 1ms/DIV ON FB1 FB = 1.235V OUT 1.8V 100k LTC2923 16.5k 35.7k RAMPBUF STATUS V 16.5k IN 3.3V TRACK1 SDO 2.5V IN 1V/DIV 887k 1.8V 13k DC/DC TRACK2 FB2 FB = 0.8V OUT 2.5V GND 412k 887k 412k 2923 TA02b 1ms/DIV 2923 TA01 2923fb 1 For more information www.linear.com/LTC2923 ion pplica ions pplica ion uresLTC2923 a Te Maxi Mu M r a T (Note 1) Supply Voltage (V ) ................................ 0.3V to 10V Average Current CC Input Voltages TRACK1, TRACK2 ................................................5mA ON ......................................................... 0.3V to 10V FB1, FB2 ...............................................................5mA TRACK1, TRACK2 ........................0.3V to V + 0.3V RAMPBUF ............................................................5mA CC RAMP .............................................0.3V to V + 1V Operating Temperature Range CC Output Voltages LTC2923C ................................................ 0C to 70C FB1, FB2, SDO, STATUS ......................... 0.3V to 10V LTC2923I .............................................40C to 85C RAMPBUF ....................................0.3V to V + 0.3V Storage Temperature Range .................. 65C to 150C CC GATE (Note 2) ......................................0.3V to 11.5V Lead Temperature (Soldering, 10 sec) MS Package ......................................................300C K / D F Ma T TOP VIEW V 1 12 RAMP CC ON 2 11 GATE TOP VIEW V 1 10 RAMP TRACK1 3 10 STATUS CC ON 2 9 GATE 13 TRACK2 4 9 SDO TRACK1 3 8 FB1 TRACK2 4 7 FB2 RAMPBUF 5 8 FB1 RAMPBUF 5 6 GND GND 6 7 FB2 MS PACKAGE 10-LEAD PLASTIC MSOP DE12 PACKAGE T = 125C, = 120C/W JMAX JA 12-LEAD (4mm 3mm) PLASTIC DFN T = 125C, = 43C/W JMAX JA EXPOSED PAD (PIN 13) (PCB GND CONNECTION OPTIONAL) o r Der i n F Ma T