Datasheet LTC7891 (Analog Devices) - 5

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LTC7891 SPECIFICATIONS Table 1. Electrical Characteristics (Continued) Parameter Symbol Test Conditions/Comments Min Typ Max Unit
SPREAD SPECTRUM OSCILLATOR AND PHASE-LOCKED LOOP Fixed Frequency fOSC PLLIN/SPREAD = 0 V Low Fixed Frequency FREQ voltage (VFREQ) = 0 V, TA = 25°C 320 370 420 kHz High Fixed Frequency VFREQ = INTVCC 2.0 2.25 2.5 MHz Programmable Frequency FREQ = 374 kΩ 100 kHz FREQ = 75 kΩ, TA = 25°C 450 500 550 kHz FREQ = 12.5 kΩ 3 MHz Synchronizable Frequency Range fSYNC PLLIN/SPREAD = external clock 0.1 3 MHz PLLIN Input High Level 2.2 V PLLIN Input Low Level 0.5 V Spread Spectrum Frequency Range PLLIN/SPREAD = INTVCC (Relative to fOSC) Minimum Frequency 0 % Maximum Frequency 20 % PGOOD OUTPUT PGOOD Voltage Low PGOOD current (IPGOOD) = 2 mA, TA = 25°C 0.2 0.4 V PGOOD Leakage Current PGOOD = 5 V ±1 µA PGOOD Trip Level VFB rising, TA = 25°C 7 10 13 % VFB with Respect to Set Regulated Voltage Hysteresis 1.6 % VFB falling, TA = 25°C –13 –10 –7 % Hysteresis 1.6 % PGOOD Delay for Reporting a Fault 25 µs 1 This specification is not tested in production. 2 The LTC7891 is tested in a feedback loop that servos VITH to a specified voltage and measures the resultant VFB. 3 SENSE− bias current is reflected to the input supply by the formula IVIN = ISENSE− × VOUT/(VIN × η), where η is the efficiency. 4 Rise and fall times are measured using 10% and 90% levels. Delay times are measured using 50% levels. 5 SW falling to BGxx rising and BGxx falling to SW rising delay times are measured at the rising and falling thresholds on SW and BGxx of approximately 1 V. See Figure 41 and Figure 42. 6 The minimum on-time condition specified for inductor peak-to-peak ripple current is >40% of the maximum load current (IMAX) (see the Minimum On Time Considerations section).
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Document Outline Features Applications Typical Application Circuit General Description Specifications Electrical Characteristics Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Functional Diagram Main Control Loop Power and Bias Supplies (VIN, EXTVCC, DRVCC, and INTVCC) High-Side Bootstrap Capacitor Dead Time Control (DTCA and DTCB Pins) Startup and Shutdown (RUN and TRACK/SS Pins) Light Load Operation: Burst Mode Operation, Pulse Skipping Mode, or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum, and Phase-Locked Loop (FREQ and PLLIN/SPREAD Pins) Output Overvoltage Protection Foldback Current Power Good 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 Dead Time Control (DTCA and DTCB Pins) DTCx Pins Tied to GND (Adaptive Dead Time Control) DTCx Pins Tied to INTVCC (Smart Near Zero Dead Time Control) DTCx Pins Connected with a Resistor to GND Power FET Selection CIN and COUT Selection Setting the Output Voltage RUN Pin and Undervoltage Lockout Soft Start and Tracking (TRACK/SS Pin) INTVCC Regulators (OPTI-DRIVE) Topside FET Driver Supply (CB) Minimum On Time Considerations Fault Conditions: Current Limit and Foldback Fault Conditions: Overvoltage Protection Fault Conditions: Overtemperature Protection Phase-Locked Loop and Frequency Synchronization Efficiency Considerations Checking Transient Response Design Example PCB Layout Checklist PCB Layout Debugging Typical Applications Related Products Outline Dimensions Ordering Guide Evaluation Boards Automotive Products