ltc3586 Linear Technology Corporation, ltc3586 Datasheet - Page 32

• Manufacturer Part Number: ltc3586
• Description: High Ef? Ciency Usb Power Manager With Boost, Buck-boost And Dual Bucks
• Manufacturer: Linear Technology Corporation

LTC3586
APPLICATIONS INFORMATION
32
Figure 9. Error Amplifi er with Type III Compensation
Figure 8. Error Amplifi er with Type I Compensation
Figure 10. Boost Converter Application Circuit
LTC3586
ERROR
AMP
V
IN4
V
SW4
OUT4
+
–
ERROR
FB4
AMP
+
–
FB3
V
0.8V
C3
L
C
PL
FB3
V
0.8V
C3
R2
C1
C2
C
P1
R1
R2
3586 F10
V
V
OUT3
OUT3
R1
R
3586 F09
R1
R2
C
FB
3586 F08
OUT
R3
C3
Boost Regulator Output Voltage Programming
The boost regulator can be programmed for output volt-
ages up to 5V. The output voltage is programmed using a
resistor divider from the V
pin such that:
where V
Typical values for R1 are in the range of 40k to 1M. Too
small a resistor will result in a large quiescent current in the
feedback network and may hurt effi ciency at low current.
Too large a resistor coupled with the FB4 pin capacitance
will create an additional pole which may result in loop
instability. If large values are chosen for R1 and R2, a
phase-lead capacitor C
the transient response. Recommended values for C
in the range of 2pF to 10pF.
Printed Circuit Board Layout Considerations
In order to be able to deliver maximum current under
all conditions, it is critical that the Exposed Pad on the
backside of the LTC3586 package be soldered to the PC
board ground. Failure to make thermal contact between
the Exposed Pad on the backside of the package and the
copper board will result in higher thermal resistances.
V
OUT
4
FB4
=
V
is 0.8V. See Figure 10.
FB
4
⎛
⎜
⎝
R
R
2
1
+
1
PL
⎞
⎟
⎠
across resistor R1 can improve
OUT4
pin connected to the FB4
PL
3586f
are