Datasheet LTC7813 (Analog Devices) - 10

LTC7813
Typical perForMance characTerisTics Buck Inductor Current at Light Boost Inductor Current at Light Start-Up Load Load
FORCED CONTINUOUS MODE FORCED CONTINUOUS MODE VOUT 5V/DIV IL1 IL2 2A/DIV 2A/DIV Burst Mode OPERATION Burst Mode OPERATION RUN 5V/DIV PULSE-SKIPPING MODE PULSE-SKIPPING MODE 5ms/DIV 7813 G37 5µs/DIV 7813 G38 5µs/DIV 7813 G39 FIGURE 15 CIRCUIT FIGURE 15 CIRCUIT FIGURE 15 CIRCUIT VIN = 32V VIN = 18V VOUT = 24V VOUT = 24V IOUT = 1mA IOUT = 1mA
pin FuncTions SW1, SW2 (Pins 1, 30):
Switch Node Connections to
ITH1, ITH2 (Pins 5, 20):
Error Amplifier Outputs and Inductors. Switching Regulator Compensation Points. Each associ-
TG1, TG2 (Pins 2, 29):
High Current Gate Drives for Top ated channel’s current comparator trip point increases N-Channel MOSFETs. These are the outputs of floating with this control voltage. drivers with a voltage swing equal to DRVCC superimposed
VFB1 (Pin 6):
This pin receives the remotely sensed feedback on the switch node voltage SW. voltage for the buck controller from an external resistive
TRACK/SS1, SS2 (Pins 3, 23):
External Tracking and Soft- divider across the output. Start Input. For the buck channel, the LTC7813 regulates
SENSE1+, SENSE2+ (Pins 7, 12):
The (+) Input to the the VFB1 voltage to the smaller of 0.8V, or the voltage on Differential Current Comparators. The ITH pin voltage and the TRACK/SS1 pin. For the boost channel, the LTC7813 controlled offsets between the SENSE– and SENSE+ pins regulates the VFB2 voltage to the smaller of 1.2V, or the in conjunction with RSENSE set the current trip threshold. voltage on the SS2 pin. An internal 10µA pull-up current For the boost channel, the SENSE2+ pin supplies current source is connected to this pin. A capacitor to ground at to the current comparator. this pin sets the ramp time to final regulated output voltage.
SENSE1–, SENSE2– (Pins 8, 13):
The (–) Input to the Alternatively, a resistor divider on another voltage supply Differential Current Comparators. When SENSE1– for the connected to the TRACK/SS1 pin allows the LTC7813 buck buck channel is greater than INTV output to track the other supply during start-up. CC, the SENSE1– pin supplies current to the current comparator.
VPRG2 (Pin 4):
Channel 2 Output Control Pin. This pin
FREQ (Pin 9):
The frequency control pin for the internal sets the boost channel to adjustable output mode using VCO. Connecting this pin to GND forces the VCO to a fixed external feedback resistors or fixed 10V/12V output mode low frequency of 350kHz. Connecting this pin to INTV using internal resistive dividers. Grounding this pin allows CC forces the VCO to a fixed high frequency of 535kHz. the output to be programmed through the VFB2 pin using Other frequencies between 50kHz and 900kHz can be external resistors, regulating VFB2 to the 1.2V reference. programmed using a resistor between FREQ and GND. Floating this pin or connecting it to INTVCC programs the The resistor and an internal 20µA source current create a output to 10V or 12V (respectively), with VFB2 used to voltage used by the internal oscillator to set the frequency. sense the output voltage. 7813f 10 For more information www.linear.com/LTC7813 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagrams Operation Applications Information Typical Applications Package Description Typical Application Related Parts