LT1616 查看數據表（PDF） - Linear Technology
零件编号
产品描述 (功能)
比赛名单
LT1616 Datasheet PDF : 16 Pages
| |||
LT1616
APPLICATIO S I FOR ATIO
Shorted Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively, an LT1616 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
LT1616 is absent. This may occur in battery charging
applications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT1616’s
output. If the VIN pin is allowed to float and the SHDN pin
is held high (either by a logic signal or because it is tied to
VIN), then the LT1616’s internal circuitry will pull its
quiescent current through its SW pin. This is fine if your
system can tolerate a few mA in this state. If you ground
the SHDN pin, the SW pin current will drop to essentially
zero. However, if the VIN pin is grounded while the output
is held high, then parasitic diodes inside the LT1616 can
pull large currents from the output through the SW pin and
the VIN pin. Figure 7 shows a circuit that will run only when
the input voltage is present and that protects against a
shorted or reversed input.
PCB Layout
For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Figure 8 shows
the high current paths in the buck regulator circuit. Note
that large, switched currents flow in the power switch, the
D4
5
1
VIN
VIN
BOOST
LT1616
100k 4
6
SHDN
SW
GND
FB
100k
2
3
VOUT
BACKUP
D4: MBR0530
1616 F07
Figure 7. Diode D4 Prevents a Shorted Input from Discharging a
Backup Battery Tied to the Output; It Also Protects the Circuit from a
Reversed Input. The LT1616 Runs Only When the Input is Present
VIN SW
GND
VIN SW
GND
(a)
IC1
C1
VIN SW
GND
L1
D1
(b)
VSW
C2
1616 F08
(c)
Figure 8. Subtracting the Current When the Switch is On (a) from the Current When the Switch is Off (b) Reveals the Path of the High
Frequency Switching Current (c). Keep This Loop Small. The Voltage on the SW and BOOST Nodes Will Also be Switched; Keep These
Nodes as Small as Possible. Finally, Make Sure the Circuit is Shielded with a Local Ground Plane
11
Share Link: 