LTC3807_15 Datasheet, PDF (5/32 Pages) Linear Technology – Low IQ, Synchronous Step-Down Controller with 24V Output Voltage Capability

LTC3807
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified
operating junction temperature range, otherwise specifications are at T_A = 25°C (Note 2), V_IN = 12V, V_RUN = 5V, EXTV_CC = 0V unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
PGOOD Leakage Current
PGOOD Trip Level
V_PGOOD = 5V
V_FB with Respect to Set Regulated Voltage
V_FB Ramping Negative
Hysteresis
±1
µA
–13
–10
–7
%
2.5
%
V_FB Ramping Positive
Hysteresis
7
10
13
%
2.5
%
Delay for Reporting a Fault
25
µs
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 LTC3807 is tested under pulsed load conditions such that
T_J ≈ T_A. The LTC3807E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3807I is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC3807H is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC3807MP is tested and guaranteed over
the –55°C to 150°C operating junction temperature range. High junction
temperatures degrade operating lifetimes; operating lifetime is derated
for junction temperatures greater than 125°C. Note that the maximum
ambient temperature consistent with these specifications is determined by
specific operating conditions in conjunction with board layout, the rated
package thermal impedance and other environmental factors.
Note 3: The junction temperature (T_J, in °C) is calculated from the ambient
temperature (T_A, in °C) and power dissipation (P_D, in Watts) according to
the formula:
T_J = T_A + (P_D • θ_JA), where θ_JA is 43°C/W for the QFN or 38°C/W for the
TSSOP.
Note 4: The LTC3807 is tested in a feedback loop that servos V_ITH to a
specified voltage and measures the resultant V_FB. The specification at
85°C is not tested in production and is assured by design, characterization
and correlation to production testing at other temperatures (125°C for
the LTC3807E/LTC3807I, 150°C for the LTC3807H/LTC3807MP). For the
LTC3807MP, the specification at –40°C is not tested in production and is
assured by design, characterization and correlation to production testing
at –55°C.
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).
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency and Power Loss vs
Output Current
100 _{VIN = 12V}
BURST EFFICIENCY
90 VOUT = 3.3V
80
10000
1000
70
FCM LOSS
60
100
50
PULSE-SKIPPING
40 _LOSS
BURST LOSS
10
30
20
FCM EFFICIENCY
1
10
0
0.0001
PULSE-SKIPPING
EFFICIENCY
0.001 0.01 0.1
1
OUTPUT CURRENT (A)
0.1
10
FIGURE 12 CIRCUIT
3807 G01
Efficiency vs Output Current
100
90 ^{VOUT = 8.5V}
80
V_OUT = 3.3V
70
60
50
40
30
20
Burst Mode OPERATION
10
0 ^{VIN = 12V}
0.0001 0.001 0.01 0.1
1
10
OUTPUT CURRENT (A)
FIGURES 12, 14 CIRCUITS
3807 G02
For more information www.linear.com/LTC3807
Efficiency vs Input Voltage
100
98
V_OUT = 8.5V
96
94
92
90
88
V_OUT = 3.3V
86
84
82
80 ^{ILOAD = 2A}
0 5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
FIGURES 12, 14 CIRCUITS
3807 G03
3807f
5