LTC3785_15 Datasheet, PDF (5/20 Pages) Linear Technology – 10V, High Efficiency, Synchronous, No RSENSE Buck-Boost Controller

LTC3785
Typical Performance Characteristics T_A = 25°C, unless otherwise noted.
V_FB vs Temperature
1.2255
1.2250
1.2245
1.2240
1.2235
1.2230
1.2225
1.2220
1.2215
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3785 G07
Normalized Oscillator Frequency
vs Temperature
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3785 G08
V_IN Start-Up Voltage
vs Temperature
2.490
V_IN Burst Quiescent Current
vs Temperature
100
2.485
95
2.480
90
2.475
85
2.470
2.465
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3785 G10
80
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3785 G11
Oscillator Frequency vs RT
1200
1000
800
600
400
200
0
20
40
60
80
100
RT (kΩ)
3785 G09
OV and UV Thresholds
vs Temperature
12
10
8
OV THRESHOLD
6
4
2
0
–2
–4
UV THRESHOLD
–6
–8
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3785 G12
Pin Functions
RUN/SS (Pin 1): Run Control and Soft-Start Input. An
internal 1µA charges the soft-start capacitor and will
charge to approximately 2.5V. During a current limit fault,
the soft-start capacitor will incrementally discharge. Once
the pin drops below 1.225V the IC will enter fault mode,
turning off the outputs for 32 times the soft-start time. If
>5µA (at RUN/SS = 1.225V) is applied externally, the part
will latch off after a fault is detected. If >40µA (at RUN/SS
= 1.225V) is applied externally, current limit faults will not
discharge the SS capacitor.
V_C (Pin 2): Error Amp Output. A frequency compensa-
tion network is connected from this pin to the FB pin to
compensate the loop. See Closing the Feedback Loop in
the Applications Information section for guidelines.
FB (Pin 3): Feedback Pin. Connect resistor divider tap
here. The feedback reference voltage is typically 1.225V
The output voltage can be adjusted from 2.7V to 10V ac-
cording to the following formula:
V_OUT
=
1.225V
•
R1+ R2
R2
3785fc