Datasheet LTC3855 (Analog Devices) - 5

LTC3855 e lecTrical characTerisTics
The
l
denotes the specifications which apply over the full operating junction temperature range (E-Grade), otherwise specifications are at TA = 25°C. VIN = 15V, VRUN/SS = 5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS On Chip Driver
TG RUP TG Pull-Up RDS(ON) TG High 2.6 Ω TG RDOWN TG Pull-Down RDS(ON) TG Low 1.5 Ω BG RUP BG Pull-Up RDS(ON) BG High 2.4 Ω BG RDOWN BG Pull-Down RDS(ON) BG Low 1.1 Ω
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
Note 4:
The LTC3855 is tested in a feedback loop that servos VITH1,2 to a may cause permanent damage to the device. Exposure to any Absolute specified voltage and measures the resultant VFB1,2. Maximum Rating condition for extended periods may affect device
Note 5:
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 LTC3855E is guaranteed to meet performance specifications
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay from 0°C to 85°C. Specifications over the –40°C to 85°C operating times are measured using 50% levels. junction temperature range are assured by design, characterization and
Note 7:
The minimum on-time condition is specified for an inductor correlation with statistical process controls. The LTC3855I is guaranteed peak-to-peak ripple current ≥40% of IMAX (see Minimum On-Time to meet performance specifications over the full –40°C to 125°C operating Considerations in the Applications Information section). junction temperature range.
Note 8:
Guaranteed by design.
Note 3:
TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formulas: LTC3855UJ: TJ = TA + (PD • 33°C/W) LTC3855FE: TJ = TA + (PD • 25°C/W) Typical perForMance characTerisTics
Efficiency vs Output Current Efficiency vs Output Current Full Load Efficiency and Power and Mode and Mode Loss vs Input Voltage
100 100 90 5 90 90 1.8V Burst Mode EFFICIENCY 80 OPERATION 80 Burst Mode OPERATION 70 70 1.2V POWER LOSS (W) 85 4 60 DCM 60 V DCM V 50 IN = 12V IN = 12V V 50 OUT = 1.8V VOUT = 1.2V 1.8V 40 40 EFFICIENCY (%) CCM EFFICIENCY (%) CCM EFFICIENCY (%) 80 POWER LOSS 3 30 30 1.2V 20 20 10 10 CIRCUIT OF FIGURE 19 CIRCUIT OF FIGURE 19 CIRCUIT OF FIGURE 19 0 0 75 2 0.01 0.1 1 10 100 0.01 0.1 1 10 100 5 10 15 20 LOAD CURRENT (A) LOAD CURRENT (A) INPUT VOLTAGE (V) 3855 G23 3855 G24 3855 G24 3855f Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Block Diagram Operation Applications Information Typical Applications Package Description Related Parts