Datasheet LTC7804 (Analog Devices) - 6

link to page 15 LTC7804
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are for TA = 25°C, VBIAS = 12V, RUN = 12V, EXTVCC = 0V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
BOOST Charge Pump Available Output Current VBOOST = 16V, VSW = 12V, FREQ = 0V, 30 65 µA Forced Continuous Mode
INTVCC Low Dropout (LDO) Linear Regulator
INTVCC Regulation Point 4.95 5.15 5.35 V INTVCC Load Regulation ICC = 0mA to 50mA, VBIAS ≥ 6V 1 2 % ICC = 0mA to 50mA, VEXTVCC ≥ 6V 1 2 % EXTVCC LDO Switchover Voltage EXTVCC Rising 4.6 4.7 4.8 V EXTVCC Switchover Hysteresis 250 mV UVLO Undervoltage Lockout INTVCC Rising l 4.15 4.25 4.35 V INTVCC Falling l 3.80 3.90 4.00 V
Spread Spectrum Oscillator and Phase-Locked Loop
fOSC Low Fixed Frequency VFREQ = 0V, PLLIN/SPREAD = 0V 340 375 410 kHz High Fixed Frequency VFREQ = INTVCC, PLLIN/SPREAD = 0V l 2.0 2.25 2.5 MHz Programmable Frequency RFREQ = 374kΩ, PLLIN/SPREAD = 0V 100 kHz RFREQ = 75kΩ, PLLIN/SPREAD = 0V 450 500 550 kHz RFREQ = 12.4kΩ, PLLIN/SPREAD = 0V 3 MHz Synchronizable Frequency Range PLLIN/SPREAD = External Clock l 0.1 3 MHz 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 0 % Maximum Frequency 20 %
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 3:
The LTC7804 is tested in a feedback loop that servos VITH to a may cause permanent damage to the device. Exposure to any Absolute specified voltage and measures the resultant VFB. Maximum Rating condition for extended periods may affect device
Note 4:
Dynamic supply current is higher due to the gate charge being reliability and lifetime. delivered at the switching frequency. See Applications information.
Note 2:
The LTC7804 is tested under pulsed load conditions such
Note 5:
Rise and fall times are measured using 10% and 90% levels. Delay that TJ ≈ TA. The LTC7804E is guaranteed to meet specifications from times are measured using 50% levels. 0°C to 85°C junction temperature. Specifications over the –40°C to
Note 6:
The minimum on-time condition is specified for an inductor 125°C operating junction temperature range are assured by design, peak-to-peak ripple current >40% of I characterization and correlation with statistical process controls. The L(MAX) (See Minimum On-Time Considerations in the Applications Information section). LTC7804I is guaranteed over the –40°C to 125°C operating junction temperature range and the LTC7804H is guaranteed over the –40°C to
Note 7:
This IC includes overtemperature protection that is intended to 150°C operating junction temperature range and is tested at 150°C. High protect the device during momentary overload conditions. The maximum junction temperatures degrade operating lifetimes; operating lifetime rated junction temperature will be exceeded when this protection is active. is derated for junction temperatures greater than 125°C. Note that the Continuous operation above the specified absolute maximum operating maximum ambient temperature consistent with these specifications is junction temperature may impair device reliability or permanently damage determined by specific operating conditions in conjunction with board the device. layout, the rated package thermal impedance and other environmental
Note 8:
Do not apply a voltage or current source to these pins. They must factors. The junction temperature (TJ, in °C) is calculated from the ambient be connected to capacitive loads only, otherwise permanent damage temperature (TA, in °C) and power dissipation (PD, in Watts) according may occur. to the formula: TJ = TA + (PD • JA), where θJA (in °C/W) is the package thermal impedance. Rev. 0 6 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Main Control Loop INTVCC/EXTVCC Power Boost Supply and Dropout (BOOST and SW Pins) Shutdown and Start-Up (RUN, SS Pins) Light Load Current 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) Operation When VIN > VOUT Operation at Low Input Voltage BOOST Supply Refresh and Internal Charge Pump Applications Information SENSE+ and SENSE– Pins Low Value Resistor Current Sensing Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Power MOSFET Selection CIN and COUT Selection Setting Output Voltage RUN Pin Soft-Start (SS Pin) INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Phase-Locked Loop and Frequency Synchronization Setting the Operating Frequency Selecting the Light-Load Operating Mode Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Efficiency Considerations Checking Transient Response Design Example PC Board Layout Checklist PC Board Layout Debugging Package Description Typical Application Related Parts