Datasheet LTC7818 (Analog Devices) - 6

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ELECTRICAL CHARACTERISTICS The
l
indicates specifications which apply over the specified operating junction temperature range, otherwise specifications are for TA = 25°C, VBIAS = 12V, RUN1,2,3 > 1.25V, EXTVCC = 0V, VPRG3 = FLOAT unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
PLLIN Input High Level l 2.2 V PLLIN Input Low Level l 0.5 V Spread Spectrum Frequency Range PLLIN/SPREAD = INTVCC (Relative to fOSC) Minimum Frequency –12 % Maximum Frequency +15 %
PGOOD1 and OV3 Outputs
PGOOD1 Voltage Low IPGOOD1 = 2mA 0.2 0.4 V PGOOD1 Leakage Current VPGOOD1 = 5V ±1 µA PGOOD1 Trip Level VFB1 Rising 7 10 13 % VFB1 Relative to Set Regulation Point Hysteresis 2.5 % VFB1 Falling –13 –10 –7 % Hysteresis 2.5 % PGOOD1 Delay for Reporting a Fault 25 µs OV3 Voltage Low IOV3 = 2mA 0.2 0.4 V OV3 Leakage Current VOV3 = 5V ±1 µA OV3 Trip Level VFB3 Rising 7 10 13 % VFB3 Relative to Set Regulation Point Hysteresis 2.5 %
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings input supply current, select channel 1 to be the lowest output voltage may cause permanent damage to the device. Exposure to any Absolute greater than 3.2V and connect EXTVCC to the lowest output voltage greater Maximum Rating condition for extended periods may affect device than 4.8V. reliability and lifetime.
Note 4:
The LTC7818 is tested in a feedback loop that servos VITH1,2,3
Note 2:
The LTC7818 is tested under pulsed load conditions such to a specified voltage and measures the resultant VFB1,2,3. The that TJ ≈ TA. The LTC7818E is guaranteed to meet specifications from specifications at 0°C and 85°C are not tested in production and are 0°C to 85°C junction temperature. Specifications over the –40°C to assured by design, characterization and correlation to production testing 125°C operating junction temperature range are assured by design, at other temperatures (125°C for the LTC7818E/LTC7818I, 150°C for the characterization and correlation with statistical process controls. The LTC7818J/LTC7818H). LTC7818I is guaranteed over the –40°C to 125°C operating junction
Note 5:
Dynamic supply current is higher due to the gate charge being temperature range, and the LTC7818J/LTC7818H are guaranteed over delivered at the switching frequency. See Applications Information. the –40°C to 150°C operating junction temperature range. High junction
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay temperatures degrade operating lifetimes; operating lifetime is derated times are measured using 50% levels. for junction temperatures greater than 125°C. Note that the maximum ambient temperature consistent with these specifications is determined by
Note 7:
The minimum on-time condition is specified for an inductor specific operating conditions in conjunction with board layout, the rated peak-to-peak ripple current > 40% of IL(MAX) (See Minimum On-Time package thermal impedance and other environmental factors. The junction Considerations in the Applications Information section). temperature (T
Note 8:
This IC includes overtemperature protection that is intended to J, in °C) is calculated from the ambient temperature (TA, in °C) and power dissipation (P protect the device during momentary overload conditions. The maximum D, in Watts) according to the formula: TJ = TA + (P rated junction temperature will be exceeded when this protection is active. D • θJA), where θJA (in °C/W) is the package thermal impedance.
Note 3:
When SENSE1– ≥ 3.2V or EXTV Continuous operation above the specified absolute maximum operating CC ≥ 4.8V, VBIAS supply current is transferred to these pins to reduce the total input supply quiescent junction temperature may impair device reliability or permanently damage current. SENSE1– bias current is reflected to the buck channel 1 input the device. supply (V –
Note 9:
Do not apply a voltage or current source to these pins. They must IN1) by the formula IVIN1 = ISENSE1 • VOUT1/(VIN1 • η), where η is the efficiency. EXTV be connected to capacitive loads only, otherwise permanent damage CC bias current is similarly reflected to a buck channel input supply when biased by a buck channel output. To minimize may occur. Rev. A 6 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Main Control Loop Power and Bias Supplies (VBIAS, EXTVCC, and INTVCC) Shutdown and Start-Up (RUN1, RUN2, RUN3 and TRACK/SS1, TRACK/SS2, SS3 Pins) Light Load Operation: Burst Mode Operation, Pulse-Skipping, or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum, and Phase-Locked Loop (FREQ and PLLIN/SPREAD Pins) Boost Controller Operation When VIN > VOUT Boost Controller at Low Input Voltage Buck Controller Output Overvoltage Protection Buck Foldback Current Channel 1 Power Good (PGOOD1) Boost Overvoltage Indicator (OV3) Applications Information Inductor Value Calculation Inductor Core Selection Current Sense Selection Low Value Resistor Current Sensing Inductor DCR Current Sensing Setting the Operating Frequency Selecting the Light-Load Operating Mode Power MOSFET Selection Boost CIN and COUT Selection Buck CIN and COUT Selection Setting the Buck Output Voltage Setting Boost Output Voltage (VPRG3 Pin) RUN Pins and Undervoltage Lockout Soft-Start and Tracking (TRACK/SS1, TRACK/SS2, SS3 Pins) Single Output Two-Phase Operation INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Minimum On-Time Considerations Boost Channel Current Monitor (IMON3) Fault Conditions: Buck Current Limit and Foldback Fault Conditions: Buck Overvoltage Protection (Crowbar) Fault Conditions: Overtemperature Protection Phase-Locked Loop and Frequency Synchronization Efficiency Considerations Checking Transient Response Buck Design Example PC Board Layout Checklist PC Board Layout Debugging Typical Applications Package Description Revision History Typical Application Related Parts