Datasheet LTC3857 (Analog Devices) - 4

LTC3857
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS INTVCC Linear Regulator
VINTVCCVIN Internal VCC Voltage 6V < VIN < 38V, VEXTVCC = 0V 4.85 5.1 5.35 V VLDOVIN INTVCC Load Regulation ICC = 0mA to 50mA, VEXTVCC = 0V 0.7 1.1 % VINTVCCEXT Internal VCC Voltage 6V < VEXTVCC < 13V 4.85 5.1 5.35 V VLDOEXT INTVCC Load Regulation ICC = 0mA to 50mA, VEXTVCC = 8.5V 0.6 1.1 % VEXTVCC EXTVCC Switchover Voltage EXTVCC Ramping Positive 4.5 4.7 4.9 V VLDOHYS EXTVCC Hysteresis 250 mV
Oscillator and Phase-Locked Loop
f25kΩ Programmable Frequency RFREQ = 25k, PLLIN/MODE = DC Voltage 105 kHz f65kΩ Programmable Frequency RFREQ = 65k, PLLIN/MODE = DC Voltage 375 440 505 kHz f105kΩ Programmable Frequency RFREQ = 105k, PLLIN/MODE = DC Voltage 835 kHz fLOW Low Fixed Frequency VFREQ = 0V, PLLIN/MODE = DC Voltage 320 350 380 kHz fHIGH High Fixed Frequency VFREQ = INTVCC, PLLIN/MODE = DC Voltage 485 535 585 kHz fSYNC Synchronizable Frequency PLLIN/MODE = External Clock l 75 850 kHz
PGOOD1 and PGOOD2 Outputs
VPGL PGOOD Voltage Low IPGOOD = 2mA 0.2 0.4 V IPGOOD PGOOD Leakage Current VPGOOD = 5V ±1 μA VPG PGOOD Trip Level VFB with Respect to Set Regulated Voltage VFB Ramping Negative –13 –10 –7 % Hysteresis 2.5 % VFB with Respect to Set Regulated Voltage VFB Ramping Positive 7 10 13 % Hysteresis 2.5 % tPG Delay for Reporting a Fault 25 μs
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 3:
TJ is calculated from the ambient temperature TA and power may cause permanent damage to the device. Exposure to any Absolute dissipation PD according to the following formula: Maximum Ratings for extended periods may affect device reliability and TJ = TA + (PD • 34°C/W) lifetime.
Note 4:
The LTC3857 is tested in a feedback loop that servos VITH1,2 to a
Note 2:
The LTC3857 is tested under pulsed conditions such that specified voltage and measures the resultant VFB1,2. The specification at TJ ≈ TA. The LTC3857E is guaranteed to meet performance specifications 85°C is not tested in production. This specification is assured by design, from 0°C to 85°C. Specifications over the –40°C to 125°C operating characterization and correlation to production testing at 125°C. junction temperature range are assured by design, characterization and
Note 5:
Dynamic supply current is higher due to the gate charge being correlation with statistical process controls. The LTC3857I is guaranteed delivered at the switching frequency. See Applications information. over the full –40°C to 125°C operating junction temperature range.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay Note that the maximum ambient temperature is determined by specific times are measured using 50% levels. operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors.
Note 7:
The minimum on-time condition is specified for an inductor peak-to-peak ripple current ≥40% of IMAX (See Minimum On-Time Considerations in the Applications Information section). 3857fd 4 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS FUNCTIONAL DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY TYPICAL APPLICATION RELATED PARTS