LT4351IMS Linear Technology, LT4351IMS Datasheet
LT4351IMS
Specifications of LT4351IMS
Available stocks
Related parts for LT4351IMS
LT4351IMS Summary of contents
Page 1
... High Availability Systems Redundant Power Supplies n L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks and PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION POWER ...
Page 2
... TAPE AND REEL LT4351CMS#PBF LT4351CMS#TRPBF LT4351IMS#PBF LT4351IMS#TRPBF Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: ...
Page 3
ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T otherwise specified. SYMBOL PARAMETER I OV Input Bias Current OV V FAULT Pin On-Voltage F(ON) I FAULT Pin Leakage Current F(OFF) Boost Supply V Boost Regulation Trip Voltage BR t Boost ...
Page 4
LT4351 TYPICAL PERFORMANCE CHARACTERISTICS Undervoltage Threshold vs Temperature 310 V = 1.2V IN 308 12V IN 306 V = 20V IN 304 302 300 298 296 294 292 290 – ...
Page 5
TYPICAL PERFORMANCE CHARACTERISTICS GATE Pin Turn On and Off Waveform with 10nF Capacitor Load V GATE 2V/DIV 50ns/DIV 4.9V TO 5.1V SQUARE WAVE OUT Typical SW Pin Waveform V SW 5V/DIV 10µs/DIV V = ...
Page 6
LT4351 PIN FUNCTIONS GATE (Pin 1): MOSFET Gate Drive Pin. This pin is tied to the gate(s) of the external N-channel MOSFET(s). The GATE pin drives high when UV is above the below the V threshold and ...
Page 7
BLOCK DIAGRAM FROM INDIVIDUAL SUPPLY ENABLE QSW + – – 0. – 10.7V REG – + ...
Page 8
LT4351 OPERATION Increasingly, system designers have to deal with multiple supply sources. The multiplicity may provide parallel, redundant supplies for increased reliability or provide a means of connecting disparate supplies. In all cases the desire is for behavior like a ...
Page 9
OPERATION The on-chip boost regulator uses a constant off-time control scheme. When V is below the regulation trip DD voltage, the switch turns on after a 600ns off-time. When the switch turns on current ramps up in the inductor until ...
Page 10
LT4351 APPLICATIONS INFORMATION In that case, the resistor values are set by: UV HYST UVHYST UV FAULT V – • FAULT R2 = • – V FAULT UV V • UV ...
Page 11
APPLICATIONS INFORMATION For V less than 2V, choose a DC resistance less than 0.2Ω. IN Note that V current referred to the input supply is higher first order approximation of the input current is: 10.6 I ...
Page 12
LT4351 APPLICATIONS INFORMATION As an example, for 500nH of inductance and R 100mΩ, then: 4 • 500nF C ≥ = 200µF 2 0.1 Check vendor data for ESR and iterate to get the best value. Additional C capacitance may be ...
Page 13
APPLICATIONS INFORMATION The gate drive amplifier will attempt to regulate the voltage across the MOSFETs to 15mV. Regulation will be achieved if: 15mV R < for two MOSFETs and DS 2 • I LOAD 15mV R < for a single ...
Page 14
LT4351 APPLICATIONS INFORMATION ORing Disparate Supplies The LT4351 provides an easy solution for connecting together different types of power sources. Again, because of the low forward drop, the efficiency of the system is improved and the voltage transition between supplies ...
Page 15
APPLICATIONS INFORMATION Since the boost regulator supplies current for V current is the V supply current (3.5mA) plus the aver- DD age current to charge the gate. For a gate charge of 50nC at a 10kHz rate, this adds 0.5mA ...
Page 16
LT4351 APPLICATIONS INFORMATION Design Example The following demonstrates the calculations involved for setting design components for a 5V system that requires 5A. Two supplies are used to do this. The V be deemed in spec when it is within ±5% ...
Page 17
TYPICAL APPLICATIONS CHARGER + 12V LEAD-ACID BATTERY 10µH MBR0530 10µF + 220µF 5V SOURCE 10µF + 100µF 12V SOURCE 2ND 5V SOURCE 2ND 12V SOURCE Lead Acid Battery Backup Si4408DY 1Ω 10µF 12.7k V GATE 0.1µF IN ...
Page 18
LT4351 PACKAGE DESCRIPTION 5.23 (.206) MIN 0.305 ± 0.038 (.0120 ± .0015) TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) GAUGE PLANE 0.18 (.007) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, ...
Page 19
... Reversed orientation of N-channel MOSFETs in Typical Application drawing. Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...
Page 20
... Integrated N-Channel MOSFET, 0.5µs Turn-Off 26.5V P-Channel MOSFET 28V Range www.linear.com ● OUT 10µF 10 OUT 10k 10k STATUS 8 FAULT 100k 5% OUT LOAD 100µF 10µF 10 OUT 10k 10k 9 STATUS 8 FAULT 4351TA04 LT 1210 REV C • PRINTED IN USA LINEAR TECHNOLOGY CORPORA TION 2003 4351fc ...