LTC3850-1_15 Datasheet, PDF (5/38 Pages) Linear Technology – Dual, 2-Phase Synchronous Step-Down Switching Controller

LTC3850/LTC3850-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T_A = 25°C, V_IN = 15V, V_RUN1,2 = 5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Oscillator and Phase-Locked Loop
f_NOM
Nominal Frequency
f_LOW
Lowest Frequency
f_HIGH
Highest Frequency
R_MODE/PLLIN MODE/PLLIN Input Resistance
I_FREQ
Phase Detector Output Current
Sinking Capability
Sourcing Capability
PGOOD Output
V_FREQ = 1.2V
V_FREQ = 0V
V_FREQ ≥ 2.4V
f_MODE < f_OSC
f_MODE > f_OSC
450
500
550
kHz
210
250
290
kHz
700
780
860
kHz
250
kΩ
–13
µA
13
µA
V_PGL
I_PGOOD
V_PG
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I_PGOOD = 2mA
V_PGOOD = 5V
V_FB with Respect to Set Regulated Voltage
V_FB Ramping Negative
V_FB Ramping Positive
0.1
0.3
V
±2
µA
–5
– 7.5 –10
%
5
7.5
10
%
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 LTC3850E/LTC3850E-1 are guaranteed to meet performance
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3850I/LTC3850I-1 are
guaranteed to meet performance specifications over the –40°C to 85°C
operating temperature range.
Note 3: T_J is calculated from the ambient temperature T_A and power
dissipation P_D according to the following formulas:
LTC3850GN: T_J = T_A + (P_D • 95°C/W)
LTC3850UF: T_J = T_A + (P_D • 37°C/W)
LTC3850UFD: T_J = T_A + (P_D • 43°C/W)
Note 4: The LTC3850 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: V_SENSE(MAX) defaults to 50mV typical for the LTC3850-1.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Output Current
and Mode
100
V_IN = 12V
90 _{VOUT = 1.8V}
80
BURST
70
60
DCM
50
40
30 _CCM
20
10
0
10
100
1000
LOAD CURRENT (mA)
CIRCUIT OF FIGURE 14
10000
38501 G01
Efficiency vs Output Current
and Mode
100
90
BURST
80
70
60
DCM
50
40
30
CCM
20
10
0
10
V_IN = 12V
V_OUT = 3.3V
100
1000
10000
LOAD CURRENT (mA)
CIRCUIT OF FIGURE 14
38501 G02
Efficiency and Power Loss
vs Input Voltage
100
V_OUT = 3.3V
I_OUT = 2A
95
EFFICIENCY
90
POWER LOSS
85
80
5
10
15
20
INPUT VOLTAGE (V)
CIRCUIT OF FIGURE 14
2000
1500
1000
500
0
25
38501 G03
38501fc
5