POWER LOSS (W) LT8709 Negative Input Synchronous Multi-Topology DC/DC Controller Fea T Descrip T n Wide Negative Input Range: 4.5V to 80V The LT 8709 is a synchronous PWM controller for negative- n Rail-to-Rail Output Current Monitor and Control to-negative or negative-to-positive DC/DC conversion, n Input Voltage Regulation for High Impedance Inputs with rail-to-rail output current monitor and control. The n Power Good Indication Pin LT8709 is ideal for many local power supply designs. It n MODE Pin for Forced CCM (Continuous Conduction can be easily configured in buck, boost, buck-boost, and Mode) or Pulse-Skipping/DCM (Discontinuous inverting topologies with negative input voltages. Conduction Mode) Operation In addition, the LT8709s rail-to-rail output current sense n Switching Frequency Up to 750kHz allows the part to be configured in current limited applica- n Easily Configurable as a Buck, Boost, Buck-Boost, or tions such as battery or capacitor charging. The PG pin Inverting Converter with a Single Feedback Pin is used for power good indication. n Can be Synchronized to an External Clock n High Gain EN/FBIN Pin Accepts Slowly Varying Input The LT8709s switching frequency range can be set between Signals 100kHz and 750kHz. The part may be clocked internally n 20-Lead TSSOP Package at a frequency set by the resistor from the RT pin to the V pin, or it may be synchronized to an external clock. IN a T The LT8709 also features innovative EN/FBIN pin circuitry n High Power Negative Input, Negative Output Power that allows for slowly varying input signals and an adjust- Supplies able undervoltage lockout function. The pin is also used as n High Power Negative Input, Positive Output Power input voltage regulation to avoid collapsing a high imped- Supplies ance input supply. Additional features such as frequency n Telecom Equipment Power Supplies foldback, thermal shutdown and soft-start are integrated. n Cathodic Protection Power Supplies The LT8709 is available in a 20-lead TSSOP package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical a T 250kHz, 16V to 30V Input to 12V/8.5A Output Buck 7.3H 4m V OUT Efficiency and Power Loss 12V 8.5A vs Load Current (V = 24V) IN 150F 100 4.5 10F 2m 4.0 6 90 22F V 80 3.5 IN 3 2.2F CSP BG CSN TG 3.0 70 GND ISN 60 2.5 33k 120F + 62.5k ISP LT8709 2.0 50 EN/FBIN FBY 1.5 10k 40 2.2F 4.99k 30 1.0 INTV CC 100k MODE 20 0.5 BIAS PG 2.2F 10 0 0 1 2 3 4 5 6 7 8 9 RT INTV 2.2F EE LOAD CURRENT (A) V SYNC C 8709 TA01b 5.9k 143k V IMON SS IN 100pF 2.2nF 68nF 470nF V IN 8709 TA01a 16V TO 30V 8709f 1 For more information www.linear.com/LT8709 EFFICIENCY (%) + ion pplica ions pplica ion uresLT8709 a T e Maxi Mu M r a T (Note 1) GND Voltage with Reference to V .......... 0.3V to 80V MODE Voltage with Reference to V ....... 0.3V to 40V IN IN BIAS Voltage with Reference to V ......... 0.3V to 80V INTV Voltage with Reference to V ....... 0.3V to 7V IN CC IN BG Voltage with Reference to V ....................(Note 5) INTV Voltage with Reference to BIAS .............(Note 5) IN EE TG Voltage with Reference to BIAS ....................(Note 5) CSP Voltage with Reference to V ............ 0.3V to 2V IN RT Voltage with Reference to V ............... 0.3V to 5V CSN Voltage with Reference to V ............ 0.3V to 2V IN IN SS Voltage with Reference to V ............... 0.3V to 3V ISP Voltage ................................. ISN 0.4V to ISN + 2V IN FBY Voltage with Reference to GND ............. 3V to 0.3V ISN Voltage with Reference to V ........... 0.3V to 80V IN V Voltage with Reference to V ............... 0.3V to 2V IMON Voltage with Reference to V ....... 0.3V to 2.5V C IN IN EN/FBIN Voltage with Reference to V .... 0.3V to 80V Operating Junction Temperature Range IN SYNC Voltage with Reference to V ....... 0.3V to 5.5V LT8709E............................................. 40C to 125C IN PG Voltage with Reference to V .............. 0.3V to 7V LT8709I ............................................. 40C to 125C IN PG Current ............................................................. 1mA Storage Temperature Range .................. 65C to 150C p c F T TOP VIEW FBY 1 20 V IN V 2 19 SYNC C SS 3 18 RT PG 4 17 MODE IMON 5 16 EN/FBIN 21 V IN ISN 6 15 CSP ISP 7 14 CSN BIAS 8 13 GND INTV 9 12 INTV EE CC TG 10 11 BG FE PACKAGE 20-LEAD PLASTIC TSSOP T = 125C, = 38C/W, = 10C/W JMAX JA JC EXPOSED PAD (PIN 21) IS V , MUST BE SOLDERED TO PCB IN o r D i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8709EFE PBF LT8709EFE TRPBF LT8709FE 20-Lead Plastic TSSOP 40C to 125C LT8709IFE PBF LT8709IFE TRPBF LT8709FE 20-Lead Plastic TSSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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