Features: · PolyPhase® Valley Current Mode Controller
· Synchronizable to an External Clock with PLL
· Coincident or Ratiometric Tracking
· Sense Resistor Optional
· 2% to 90% Duty Cycle at 200kHz
· t ON(MIN) < 100ns
· True Remote Sensing Differential Amplifier
· High Efficiency at Both Light and Heavy Loads
· Power Good Output Voltage Monitor
· 0.6V ±1% Reference
· Adjustable Current Limit
· Programmable Soft-Start and Operating Frequency
· Output Overvoltage Protection
· Optional Short-Circuit Shutdown Timer
· Available in 32-Lead (5mm × 5mm) QFN and 36-Lead
SSOP PackagesApplication · Notebook Computers
·Power Supply for DSP, ASIC, Graphic ProcessorsPinout
SpecificationsInput Supply Voltage (VCC, DRVCC) .......... 7V to 0.3V
Boosted Topside Driver Supply Voltage
(BOOST1, BOOST2) .................................. 37V to 0.3V
Switch Voltage (SW1, 2) ............................. 31V to 1V
SENSE1+, SENSE2+ Voltages ...................... 31V to 1V
SENSE1, SENSE2 Voltages .................. 10V to 0.3V
ION Voltage ............................................. 31V to 0.3V
(BOOST SW) Voltages .............................7V to 0.3V
RUN/SS, PGOOD Voltages .......................... 7V to 0.3V
TRACK Voltage ............................................7V to 0.3V
VRNG Voltage ................................ VCC + 0.3V to 0.3V
ITH Voltage ............................................. 2.7V to 0.3V
VFB Voltage ............................................. 2.7V to 0.3V
INTLPF, EXTLPF Voltages ........................ 2.7V to 0.3V
VOS
+, VOS
Voltages .................................................. 7V to 0.3V
FCB Voltage ................................................ 7V to 0.3V
Operating Temperature Range (Note 4) 40°C to 85°C
Junction Temperature (Note 2) ............................ 125°C
Storage Temperature Range
UH Package ........................................ 65°C to 125°C
G Package .......................................... 65°C to 150°C
DescriptionThe LTC®3709 is a single output, dual phase, synchronous step-down switching regulator. The controller uses a constant on-time, valley current control architecture to deliver very low duty cycles without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in input supply voltage. An internal phase-lock loop allows the LTC3709 to be synchronized to an external clock.
A TRACK pin is provided for tracking or sequencing the output voltage among several LTC3709 chips or an LTC3709 and other DC/DC regulators. Soft-start is accomplished using an external timing capacitor.
Fault protection is provided by an output overvoltage comparator and an optional short-circuit shutdown timer. The current limit level is user programmable. A wide supply range allows voltages as high as 31V to step down as low as 0.6V.
LTC3709 Data Sheet
