LTC3706
16
3706fd
APPLICATIONS INFORMATION
LTC3706
78mV MAX
I
S
+
I
S
–
3706 F03a
• •
LTC3706
78mV MAX
I
S
+
I
S
–
3706 F03c
• •
Figure 3a. High Side Inductor:
Easier Layout, Low Noise, Accurate
Figure 3c. Switch Current Sensing: Easy Layout,
Accurate, Higher Efficiency, High V
OUT
Capable
Figure 3. Current Sensing Techniques
LTC3706
78mV MAX
I
S
+
I
S
–
3706 F03b
• •
LTC3706
V
CC
1.28V MAX
TRIP
5W TO
50Ω
I
S
+
I
S
–
3706 F03d
• •
•
•
Figure 3b. Low Side Inductor:
Accurate, Low Noise, High V
OUT
Capable
Figure 3d. Current Transformer:
Highest Efficiency, High V
OUT
Capable
current (high side or low side) is generally less noisy but
dissipates more power than sensing the switch current
(Figures 3a and 3b). High side inductor current sensing
provides a more convenient layout than low side (no split
ground plane), but can only be used for output voltages
up to 5.5V, due to the common mode limitations of the
current sense inputs (I
S
+
and I
S
–
). For most applications,
low side switch current sensing will be a good solution
(Figure 3c).
For high current applications where efficiency (power dis-
sipation) is very important, a current sense transformer
may be used. As shown in Figure 3d, the I
S
–
pin should
be tied off to V
CC
when a current sense transformer is
used. This causes the I
S
+
pin to become a single ended
(nondifferential) current sense input with a maximum
current sense voltage of 1.28V. Figure 3d shows a typical
application circuit using a current transformer.
