LTC4160-1 LINER [Linear Technology], LTC4160-1 Datasheet - Page 25
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LTC4160-1
Manufacturer Part Number
LTC4160-1
Description
Switching Power Manager with USB On-The-Go And Overvoltage Protection
Manufacturer
LINER [Linear Technology]
Datasheet
1.LTC4160-1.pdf
(32 pages)
APPLICATIONS INFORMATION
Hot Plugging and USB Inrush Current Limiting
The overvoltage protection circuit provides inrush current
limiting due to the long time it takes for OVGATE to fully
enhance the N-channel MOSFET. This prevents the current
from building up in the cable too quickly and dampens
out any resonant overshoot on V
observe voltage overshoot on V
LTC4160/LTC4160-1 to a lab supply if the overvoltage
protection circuit is not used. This overshoot is caused by
the inductance of the long leads from the supply to V
Twisting the wires together from the supply to V
greatly reduce the parasitic inductance of these long leads
and keep V
manufactured with the power leads in close proximity and
thus have fairly low parasitic inductance.
Hot Plugging and USB On-The-Go
If there is more than 4.3V on V
enabled, the bidirectional switching regulator will not try
to drive V
supply is then connected to V
happen depending on the properties of the external sup-
ply. If the external supply has a regulation voltage higher
than 5.1V, the bidirectional switching regulator will stop
NTCBIAS
T
R
105k
R1
12.7k
NOM
R
100k
NTC
NTC
BUS
BUS
3
4
Figure 8. Modifi ed NTC Confi guration
. If USB On-The-Go is enabled and an external
0.349 • NTCBIAS
at a safe level. USB cables are generally
0.765 • NTCBIAS
0.1V
LTC4160/LTC4160-1
NTC BLOCK
BUS
–
+
–
+
+
–
BUS
BUS
, one of three things will
BUS
when connecting the
when On-The-Go is
. It is possible to
TOO_COLD
TOO_HOT
NTC_ENABLE
41601 F08
BUS
BUS
can
.
switching and V
of the external supply. If the external supply has a lower
regulation voltage and is capable of only sourcing current,
then V
will not source current to V
For a supply that can also sink current and has a regulation
voltage less than 5.1V, the bidirectional switching regulator
will source current into the external supply in an attempt
to bring V
holds V
switching regulator will source up to 680mA into the sup-
ply. If V
70mV then the short circuit timer will shut off the switching
regulator after 7.2ms. The FAULT pin will then go low to
indicate a short circuit current fault.
V
Session Request Protocol
When two On-The-Go devices are connected, one will be
the A device and the other will be the B device depending
on whether the device is connected to a micro-A or micro-
B plug. The A device provides power to the B device and
starts as the host. To prolong battery life, the A device
can power down V
If the A device has powered down V
request the A device to power up V
session using the session request protocol (SRP). The
SRP consists of data-line pulsing and V
B device must fi rst pulse the D
device must then pulse V
respond to the data-line pulse. The A device is required
to respond to only one of the pulsing methods. USB A
devices that never power down V
respond to the SRP .
For V
the A device allows a B device to differentiate between a
powered down On-The-Go device and a powered down
standard host. The B device will send out a pulse of current
that will raise V
connected to an On-The-Go A device which must have no
more than 6.5μF . An On-The-Go A device must drive V
as soon as the current pulse raises V
device is capable of responding to V
BUS
Bypass Capacitance and USB On-The-Go
BUS
BUS
BUS
BUS
pulsing, the limit on the V
BUS
will be regulated to 5.1V. The external supply
to more than V
is held to a voltage that is less than V
up to 5.1V. As long as the external supply
BUS
BUS
LTC4160/LTC4160-1
BUS
to a voltage between 2.1 and 5.25V if
will be held at the regulation voltage
when the BUS is not being used.
BUS
OUT
BUS
only if the A device does not
.
+ 70mV, the bidirectional
+
or D
BUS
BUS
BUS
BUS
BUS
BUS
–
are not required to
, the B device can
data lines. The B
BUS
above 2.1V if the
pulsing.
and start a new
capacitance on
pulsing. The
25
OUT
41601f
BUS
+