1307B View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
1307B Datasheet PDF : 20 Pages
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APPLICATIO S I FOR ATIO
VOUT
200mV/DIV
AC COUPLED
VOUT
200mV/DIV
AC COUPLED
LT1307/LT1307B
IL
51mA
1mA
5ms/DIV
1307 F11a
Figure 11a. VC Pin Left Unconnected. Output Ripple
Voltage is 300mVP-P Under Load
VOUT
200mV/DIV
AC COUPLED
IL
51mA
1mA
5ms/DIV
1307 F11b
Figure 11b. Inclusion of a 100k/22nF Series RC on VC
Pin Results in Overdamped Stable Response
VOUT
200mV/DIV
AC COUPLED
IL
51mA
1mA
1ms/DIV
1307 F11a
Figure 11c. Reducing C to 2nF Speeds Up Response,
Although Still Overdamped
IL
51mA
1mA
500µs/DIV
1307 F11b
Figure 11d. A 100k/200pF Series RC Shows Some
Underdamping
VOUT
200mV/DIV
AC COUPLED
IL
51mA
1mA
1ms/DIV
1307 F11b
Figure 11e. A 100k/680pF RC Provides Optimum
Settling Time with No Ringing
underdamping. Now settling time is about 300µs. Increas-
ing C to 680pF results in the response shown in Figure 11e.
This response has minimum settling time with no over-
shoot or underdamping.
Converters using a 2-cell input need more capacitance at
the output. This added capacitance moves in the output
pole, requiring added C at the VC pin network to prevent
loop oscillation.
Observant readers will notice R has been set to 100k for all
the photos in Figure 11. Usable R values can be found in
the 10k to 500k range, but after too many trips to the
resistor bins, 100k wins.
1307fa
11
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