LTC1646CGN#TRPBF Linear Technology, LTC1646CGN#TRPBF Datasheet - Page 14
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LTC1646CGN#TRPBF
Manufacturer Part Number
LTC1646CGN#TRPBF
Description
IC CNTRLR HOTSWAP PCIDUAL 16SSOP
Manufacturer
Linear Technology
Type
Hot-Swap Controllerr
Datasheet
1.LTC1646CGNPBF.pdf
(20 pages)
Specifications of LTC1646CGN#TRPBF
Applications
CompactPCI™
Internal Switch(s)
No
Voltage - Supply
3.3V, 5V
Operating Temperature
0°C ~ 70°C
Mounting Type
Surface Mount
Package / Case
16-SSOP (0.150", 3.90mm Width)
Linear Misc Type
Positive Low Voltage
Family Name
LTC1646
Package Type
SSOP N
Operating Supply Voltage (min)
2.7V
Operating Supply Voltage (max)
7V
Operating Temperature (min)
0C
Operating Temperature (max)
70C
Operating Temperature Classification
Commercial
Product Depth (mm)
3.99mm
Product Height (mm)
1.5mm
Mounting
Surface Mount
Pin Count
16
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
APPLICATIO S I FOR ATIO
LTC1646
(RTOL = ±1%, ±2% or ±5%) and standard sense resistor
values. Equation 7 can be used to calculate the nominal
value from the maximum value found by Equation 6:
Often, the result of Equation 7 may not yield a standard
sense resistor value. In this case, two sense resistors with
the same RTOL can be connected in parallel to yield
R
The last step requires calculating a new value for
I
R
breaker threshold, V
for I
for I
selected and the process repeated. The new value for
I
Example : A 5V supply exhibits a nominal 5A load with a
maximum load current of 6.8A (I
sense resistors with ±5% RTOL will be used. According to
Equation 6, V
The nominal sense resistor value is (Equation 7):
And the new current-limit trip point is Equation 8:
14
TRIP(MAX)
TRIP(MAX, NEW)
SENSE(NOM)
SENSE
I
where R
R
TRIP MAX NEW
R
R
TRIP(MAX, NEW)
SENSE NOM
TRIP(MAX)
SENSE MAX
SENSE NOM
(
(R
(I
(
(
(
SENSE(MIN)
SENSE MIN
TRIP(MAX, NEW)
,
.
CB(MIN)
, a larger sense resistor value should be
)
)
)
is given by Equation 8:
)
=
=
(
=
=
be much greater than the design value
I
R
R
U
1
1
TRIP MAX
V
R
CB(MAX)
SENSE MAX
= 50mV and R
SENSE MAX
+
) and the upper limit for the circuit
+
)
CB MIN
V
SENSE MIN
=
⎛
⎜
⎝
⎛
⎜
⎝
CB MAX
(
(
RTOL
RTOL
R
100
100
(
U
) based on a minimum value for
SENSE NOM
(
(
(
)
. Should the calculated value
)
⎞
⎟
⎠
)
=
⎞
⎟
⎠
)
)
)
(
50
=
6 8
LOAD(MAX)
SENSE(MAX)
.
W
mV
1
0 0074
A
+
)
.
• –
⎛
⎜
⎝
⎡
⎢
⎣
=
100
1
5
0 0074
Ω
.
⎛
⎜
⎝
⎞
⎟
⎠
= 6.8A), and
RTOL
is given by:
100
=
U
0 007
Ω
.
⎞
⎟
⎠
⎤
⎥
⎦
(7)
( )
Ω
8
Since I
R
to lower I
I
Output Voltage Monitor
The status of both 5V and 3.3V output voltages is moni-
tored by the power good function. In addition, the PCI_RST#
signal is logically combined on-chip with the HEALTHY#
signal to create LOCAL_PCI_RST# (see Table 4).
Table 4. LOCAL_PCI_RST# Truth Table
If either of the output voltages drop below the power good
threshold for more than 50µs, the HEALTHY# signal will be
pulled high and the LOCAL_PCI_RST# signal will be pulled
low.
Precharge
The PRECHARGE input and DRIVE output pins are in-
tended for use in generating the 1V precharge voltage that
is used to bias the bus I/O connector pins during board
insertion. The LTC1646 is also capable of generating
precharge voltages other than 1V. Figure 8 shows a circuit
that can be used in applications requiring a precharge
voltage less than 1V. The circuit in Figure 9 can be used for
applications that need precharge voltages greater than 1V.
Table 5 lists suggested resistor values for R1 and R2 vs
precharge voltage for the application circuits shown in
Figures 8 and 9.
LOAD(MAX)
SENSE
PCI_RST#
I
R
TRIP MAX NEW
SENSE N M
LO
LO
HI
HI
TRIP(MAX, NEW)
should be selected and the process repeated again
(
TRIP(MAX, NEW)
(
.
0
,
V
CB MAX
)
• –
(
)
⎡
⎢
⎣
=
1
HEALTHY#
R
)
⎛
⎜
⎝
V
SENSE MIN
LO
LO
HI
HI
> I
RTOL
CB MAX
100
without substantially affecting
(
LOAD(MAX)
(
⎞
⎟
⎠
)
⎤
⎥
⎦
)
=
=
0 0065
65
, a larger value for
.
mV
LOCAL_PCI_RST#
=
LO
LO
LO
HI
9 8
.
A
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