LTC3855_15 Datasheet, PDF (5/44 Pages) Linear Technology – Dual, Multiphase Synchronous DC/DC Controller with Differential Remote Sense

LTC3855
Electrical Characteristics The l denotes the specifications which apply over the full operating
junction temperature range (E-Grade), otherwise specifications are at T_A = 25°C. V_IN = 15V, V_RUN/SS = 5V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP MAX UNITS
On Chip Driver
TG R_UP
TG R_DOWN
BG R_UP
BG R_DOWN
TG Pull-Up R_DS(ON)
TG Pull-Down R_DS(ON)
BG Pull-Up R_DS(ON)
BG Pull-Down R_DS(ON)
TG High
TG Low
BG High
BG Low
2.6
Ω
1.5
Ω
2.4
Ω
1.1
Ω
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3855E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3855I is guaranteed
to meet performance specifications over the full –40°C to 125°C operating
junction temperature range.
Note 3: T_J is calculated from the ambient temperature T_A and power
dissipation P_D according to the following formulas:
LTC3855UJ: T_J = T_A + (P_D • 33°C/W)
LTC3855FE: T_J = T_A + (P_D • 25°C/W)
Note 4: The LTC3855 is tested in a feedback loop that servos V_ITH1,2 to a
specified voltage and measures the resultant V_FB1,2.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7: The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ≥40% of I_MAX (see Minimum On-Time
Considerations in the Applications Information section).
Note 8: Guaranteed by design.
Typical Performance Characteristics
Efficiency vs Output Current
and Mode
100
90 _{Burst Mode}
80 OPERATION
70
60
DCM
50
V_IN = 12V
V_OUT = 1.8V
40
CCM
30
20
10
0
0.01
CIRCUIT OF FIGURE 19
0.1
1
10
LOAD CURRENT (A)
100
3855 G23
Efficiency vs Output Current
and Mode
100
90
80
Burst Mode
OPERATION
70
60
DCM
50
V_IN = 12V
V_OUT = 1.2V
40
CCM
30
20
10
0
0.01
CIRCUIT OF FIGURE 19
0.1
1
10
LOAD CURRENT (A)
100
3855 G24
Full Load Efficiency and Power
Loss vs Input Voltage
90
5
1.8V
EFFICIENCY
1.2V
85
4
1.8V
80
POWER LOSS
3
1.2V
CIRCUIT OF FIGURE 19
75
5
10
15
INPUT VOLTAGE (V)
2
20
3855 G24
3855f