Datasheet LTC3868 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | Low IQ, Dual 2-Phase Synchronous Step-Down Controller |
| Pages / Page | 38 / 8 — TYPICAL PERFORMANCE CHARACTERISTICS. Latchoff Thresholds. INTVCC and … |
| File Format / Size | PDF / 406 Kb |
| Document Language | English |
TYPICAL PERFORMANCE CHARACTERISTICS. Latchoff Thresholds. INTVCC and EXTVCC vs Load Current. vs Temperature
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LTC3868
TYPICAL PERFORMANCE CHARACTERISTICS Latchoff Thresholds INTVCC and EXTVCC vs Load Current vs Temperature
5.20 2.3 VIN = 12V 2.2 5.15 2.1 ARMING THRESHOLD 2.0 5.10 1.9 1.8 VOLTAGE (V) EXTVCC = 0V VOLTAGE (V) 1.7 CC 5.05 CC 1.6 LATCH-OFF THRESHOLD INTV INTV EXTVCC = 8V 1.5 5.00 1.4 1.3 4.95 1.2 0 20 40 60 80 100 120 140 160 180 200 –45 –20 5 30 55 80 105 130 LOAD CURRENT (mA) TEMPERATURE (°C) 3868 G26 3868 G27
PIN FUNCTIONS SENSE1–, SENSE2– (Pin 1, Pin 9):
The (–) Input to the
CLKOUT (Pin 4):
Output clock signal available to daisy- Differential Current Comparators. When greater than chain other controller ICs for additional MOSFET driver INTVCC – 0.5V, the SENSE– pin supplies current to the stages/phases. The output levels swing from INTVCC to current comparator. ground.
FREQ (Pin 2):
The Frequency Control Pin for the Internal
PLLIN/MODE (Pin 5):
External Synchronization Input to VCO. Connecting this pin to GND forces the VCO to a fixed Phase Detector and Forced Continuous Mode Input. When low frequency of 350kHz. Connecting this pin to INTVCC an external clock is applied to this pin, the phase-locked forces the VCO to a fixed high frequency of 535kHz. loop will force the rising TG1 signal to be synchronized Other frequencies between 50kHz and 900kHz can be with the rising edge of the external clock. When not syn- programmed using a resistor between FREQ and GND. chronizing to an external clock, this input, which acts on An internal 20µA pull-up current develops the voltage to both controllers, determines how the LTC3868 operates at be used by the VCO to control the frequency light loads. Pulling this pin to ground selects Burst Mode
PHASMD (Pin 3):
Control input to phase selector which operation. An internal 100k resistor to ground also invokes determines the phase relationships between control- Burst Mode operation when the pin is floated. Tying this pin ler 1, controller 2 and the CLKOUT signal. Pulling this to INTVCC forces continuous inductor current operation. pin to ground forces TG2 and CLKOUT to be out of Tying this pin to a voltage greater than 1.2V and less than phase 180° and 60° with respect to TG1. Connecting INTVCC – 1.3V selects pulse-skipping operation. this pin to INTVCC forces TG2 and CLKOUT to be out
SGND (Pin 6, Exposed Pad Pin 33):
Small-signal ground of phase 240° and 120° with respect to TG1. Floating common to both controllers, must be routed separately this pin forces TG2 and CLKOUT to be out of phase from high current grounds to the common (–) terminals 180° and 90° with respect to TG1. Refer to the Table 1. of the CIN capacitors. The exposed pad must be soldered to the PCB for rated thermal performance. 3868fe 8 For more information www.linear.com/LTC3868 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Typical Performance Characteristics Pin Functions Operation Package Description Typical Application Related Parts
TYPICAL PERFORMANCE CHARACTERISTICS Latchoff Thresholds INTVCC and EXTVCC vs Load Current vs Temperature
5.20 2.3 VIN = 12V 2.2 5.15 2.1 ARMING THRESHOLD 2.0 5.10 1.9 1.8 VOLTAGE (V) EXTVCC = 0V VOLTAGE (V) 1.7 CC 5.05 CC 1.6 LATCH-OFF THRESHOLD INTV INTV EXTVCC = 8V 1.5 5.00 1.4 1.3 4.95 1.2 0 20 40 60 80 100 120 140 160 180 200 –45 –20 5 30 55 80 105 130 LOAD CURRENT (mA) TEMPERATURE (°C) 3868 G26 3868 G27
PIN FUNCTIONS SENSE1–, SENSE2– (Pin 1, Pin 9):
The (–) Input to the
CLKOUT (Pin 4):
Output clock signal available to daisy- Differential Current Comparators. When greater than chain other controller ICs for additional MOSFET driver INTVCC – 0.5V, the SENSE– pin supplies current to the stages/phases. The output levels swing from INTVCC to current comparator. ground.
FREQ (Pin 2):
The Frequency Control Pin for the Internal
PLLIN/MODE (Pin 5):
External Synchronization Input to VCO. Connecting this pin to GND forces the VCO to a fixed Phase Detector and Forced Continuous Mode Input. When low frequency of 350kHz. Connecting this pin to INTVCC an external clock is applied to this pin, the phase-locked forces the VCO to a fixed high frequency of 535kHz. loop will force the rising TG1 signal to be synchronized Other frequencies between 50kHz and 900kHz can be with the rising edge of the external clock. When not syn- programmed using a resistor between FREQ and GND. chronizing to an external clock, this input, which acts on An internal 20µA pull-up current develops the voltage to both controllers, determines how the LTC3868 operates at be used by the VCO to control the frequency light loads. Pulling this pin to ground selects Burst Mode
PHASMD (Pin 3):
Control input to phase selector which operation. An internal 100k resistor to ground also invokes determines the phase relationships between control- Burst Mode operation when the pin is floated. Tying this pin ler 1, controller 2 and the CLKOUT signal. Pulling this to INTVCC forces continuous inductor current operation. pin to ground forces TG2 and CLKOUT to be out of Tying this pin to a voltage greater than 1.2V and less than phase 180° and 60° with respect to TG1. Connecting INTVCC – 1.3V selects pulse-skipping operation. this pin to INTVCC forces TG2 and CLKOUT to be out
SGND (Pin 6, Exposed Pad Pin 33):
Small-signal ground of phase 240° and 120° with respect to TG1. Floating common to both controllers, must be routed separately this pin forces TG2 and CLKOUT to be out of phase from high current grounds to the common (–) terminals 180° and 90° with respect to TG1. Refer to the Table 1. of the CIN capacitors. The exposed pad must be soldered to the PCB for rated thermal performance. 3868fe 8 For more information www.linear.com/LTC3868 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Typical Performance Characteristics Pin Functions Operation Package Description Typical Application Related Parts
