Datasheet LTC3835-1 (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | Low IQ Synchronous Step-Down Controller |
| Pages / Page | 28 / 7 — TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. … |
| File Format / Size | PDF / 299 Kb |
| Document Language | English |
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Undervoltage Lockout Threshold. Oscillator Frequency
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LTC3835-1
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Undervoltage Lockout Threshold Oscillator Frequency Shutdown Current vs Temperature vs Input Voltage vs Temperature
4.2 404 12 4.1 402 10 4.0 3.9 400 8 RISING 3.8 3.7 398 6 VOLTAGE (V) CC 3.6 396 4 INTV 3.5 FREQUENCY (kHz) FALLING SHUTDOWN CURRENT (μA) 3.4 394 2 3.3 3.2 392 0 –45 –30 –15 0 15 30 45 60 75 90 5 10 15 20 25 30 35 –45 –30 –15 0 15 30 45 60 75 90 TEMPERATURE (°C) INPUT VOLTAGE (V) TEMPERATURE (°C) 38351 G25 38351 G26 38351 G27
PIN FUNCTIONS (DHC Package/GN Package) PLLLPF (Pin 1/Pin 1):
The phase-locked loop’s lowpass fi lter
BG (Pin 7/Pin 7):
High Current Gate Drive for Bottom is tied to this pin when synchronizing to an external clock. (Synchronous) N-Channel MOSFET. Voltage swing at this Alternatively, tie this pin to GND, INTVCC or leave fl oating to pin is from ground to INTVCC. select 250kHz, 530kHz or 400kHz switching frequency.
INTVCC (Pin 8/Pin 8):
Output of the Internal Linear Low
ITH (Pin 2/Pin 2):
Error Amplifi er Outputs and Switching Dropout Regulator. The driver and control circuits are Regulator Compensation Points. The current comparator powered from this voltage source. Must be decoupled to trip point increases with this control voltage. power ground with a minimum of 4.7μF tantalum or other
TRACK/SS (Pin 3/Pin 3):
External Tracking and Soft-Start low ESR capacitor. Input. The LTC3835-1 regulates the VFB voltage to the smaller
VIN (Pin 9/Pin 9):
Main Supply Pin. A bypass capacitor of 0.8V or the voltage on the TRACK/SS pin. A internal 1μA should be tied between this pin and the signal ground pin. pull-up current source is connected to this pin. A capacitor
SW (Pin 10/Pin 10):
Switch Node Connections to Inductor. to ground at this pin sets the ramp time to fi nal regulated Voltage swing at this pin is from a Schottky diode (external) output voltage. Alternatively, a resistor divider on another voltage drop below ground to V voltage supply connected to this pin allows the LTC3835-1 IN. output to track the other supply during start-up.
TG (Pin 11/Pin 11):
High Current Gate Drive for Top N-Channel MOSFET. These are the outputs of fl oating drivers
VFB (Pin 4/Pin 4):
Receives the remotely sensed feedback volt- with a voltage swing equal to INTV age from an external resistive divider across the output. CC – 0.5V superimposed on the switch node voltage SW.
SGND (Pin 5/Pin 5):
Small-Signal Ground. Must be routed
BOOST (Pin 12/Pin 12):
Bootstrapped Supply to the Topside separately from high current grounds to the common (–) Floating Driver. A capacitor is connected between the terminals of the input capacitor. BOOST and SW pins and a Schottky diode is tied between
PGND (Pin 6/Pin 6):
Driver Power Ground. Connects to the the BOOST and INTVCC pins. Voltage swing at the BOOST source of bottom (synchronous) N-channel MOSFET, anode pin is from INTVCC to (VIN + INTVCC). of the Schottky rectifi er and the (–) terminal of CIN. 38351fc 7
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. Undervoltage Lockout Threshold Oscillator Frequency Shutdown Current vs Temperature vs Input Voltage vs Temperature
4.2 404 12 4.1 402 10 4.0 3.9 400 8 RISING 3.8 3.7 398 6 VOLTAGE (V) CC 3.6 396 4 INTV 3.5 FREQUENCY (kHz) FALLING SHUTDOWN CURRENT (μA) 3.4 394 2 3.3 3.2 392 0 –45 –30 –15 0 15 30 45 60 75 90 5 10 15 20 25 30 35 –45 –30 –15 0 15 30 45 60 75 90 TEMPERATURE (°C) INPUT VOLTAGE (V) TEMPERATURE (°C) 38351 G25 38351 G26 38351 G27
PIN FUNCTIONS (DHC Package/GN Package) PLLLPF (Pin 1/Pin 1):
The phase-locked loop’s lowpass fi lter
BG (Pin 7/Pin 7):
High Current Gate Drive for Bottom is tied to this pin when synchronizing to an external clock. (Synchronous) N-Channel MOSFET. Voltage swing at this Alternatively, tie this pin to GND, INTVCC or leave fl oating to pin is from ground to INTVCC. select 250kHz, 530kHz or 400kHz switching frequency.
INTVCC (Pin 8/Pin 8):
Output of the Internal Linear Low
ITH (Pin 2/Pin 2):
Error Amplifi er Outputs and Switching Dropout Regulator. The driver and control circuits are Regulator Compensation Points. The current comparator powered from this voltage source. Must be decoupled to trip point increases with this control voltage. power ground with a minimum of 4.7μF tantalum or other
TRACK/SS (Pin 3/Pin 3):
External Tracking and Soft-Start low ESR capacitor. Input. The LTC3835-1 regulates the VFB voltage to the smaller
VIN (Pin 9/Pin 9):
Main Supply Pin. A bypass capacitor of 0.8V or the voltage on the TRACK/SS pin. A internal 1μA should be tied between this pin and the signal ground pin. pull-up current source is connected to this pin. A capacitor
SW (Pin 10/Pin 10):
Switch Node Connections to Inductor. to ground at this pin sets the ramp time to fi nal regulated Voltage swing at this pin is from a Schottky diode (external) output voltage. Alternatively, a resistor divider on another voltage drop below ground to V voltage supply connected to this pin allows the LTC3835-1 IN. output to track the other supply during start-up.
TG (Pin 11/Pin 11):
High Current Gate Drive for Top N-Channel MOSFET. These are the outputs of fl oating drivers
VFB (Pin 4/Pin 4):
Receives the remotely sensed feedback volt- with a voltage swing equal to INTV age from an external resistive divider across the output. CC – 0.5V superimposed on the switch node voltage SW.
SGND (Pin 5/Pin 5):
Small-Signal Ground. Must be routed
BOOST (Pin 12/Pin 12):
Bootstrapped Supply to the Topside separately from high current grounds to the common (–) Floating Driver. A capacitor is connected between the terminals of the input capacitor. BOOST and SW pins and a Schottky diode is tied between
PGND (Pin 6/Pin 6):
Driver Power Ground. Connects to the the BOOST and INTVCC pins. Voltage swing at the BOOST source of bottom (synchronous) N-channel MOSFET, anode pin is from INTVCC to (VIN + INTVCC). of the Schottky rectifi er and the (–) terminal of CIN. 38351fc 7
