LT1054CSW#TRMPBF Linear Technology, LT1054CSW#TRMPBF Datasheet - Page 8

LT1054CSW#TRMPBF

Manufacturer Part Number
LT1054CSW#TRMPBF
Description
Manufacturer
Linear Technology
Type
Inverting/Step Upr
Datasheet

Specifications of LT1054CSW#TRMPBF

Operating Supply Voltage (min)
3.5V
Operating Supply Voltage (max)
15V
Operating Temp Range
0C to 100C
Operating Temperature Classification
Commercial
Package Type
SOIC W
Pin Count
16
Mounting
Surface Mount
Output Voltage
AdjV
Output Current
100mA
Lead Free Status / RoHS Status
Compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LT1054CSW#TRMPBFLT1054CSW
Manufacturer:
LT/凌特
Quantity:
20 000
Company:
Part Number:
LT1054CSW#TRMPBFLT1054CSW#PBF
Manufacturer:
LINEAR/凌特
Quantity:
20 000
APPLICATIONS
LT1054/LT1054L
20k or greater because the reference output current is
limited to 100 A. R2 should be chosen to be in the range
of 100k to 300k. For optimum results the ratio of C
is recommended to be 1/10. C1, required for good load
regulation at light load currents, should be 0.002 F for all
output voltages.
A new die layout was required to fit into the physical
dimensions of the S8 package. Although the new die of the
LT1054CS8 will meet all the specifications of the existing
LT1054 data sheet, subtle differences in the layout of the
new die require consideration in some application cir-
cuits. In regulating mode circuits using the 1054CS8 the
nominal values of the capacitors, C
approximately equal for proper operation at elevated
junction temperatures. This is different from the earlier
part. Mismatches within normal production tolerances
for the capacitors are acceptable. Making the nominal
capacitor values equal will ensure proper operation at
elevated junction temperatures at the cost of a small
degradation in the transient response of regulator cir-
cuits. For unregulated circuits the values of C
are normally equal for all packages. For S8 applications
assistance in unusual applications circuits, please consult
the factory.
It can be seen from the circuit block diagram that the
maximum regulated output voltage is limited by the supply
R2
R1
R2 = 20k
8
WHERE V
FOR EXAMPLE: TO GET V
PIN OF THE LT1054, CHOOSE R1 = 20k, THEN
*CHOOSE THE CLOSEST 1% VALUE
=
RESTART SHUTDOWN
V
REF
2
R3
R4
|
REF
V
2.5V
OUT
– 40mV
2
= 2.5V NOMINAL
|
–5V
|
– 40mV
|
+ 1
+ 1
OUT
|
TANTALUM
1.21V
V
= –5V REFERRED TO THE GROUND
U
= 102.6k*
OUT
|
10 F
+ 1
C
IN
INFORMATION
Figure 5
U
+
FB/SHDN
CAP
GND
CAP
W
IN
LT1054
+
and C
V
V
V
OSC
OUT
REF
OUT
V
+
OUT
+
V
IN
IN
U
, must be
and C
C
100 F
TANTALUM
+
OUT
2.2 F
IN
R1
R2
C1
/C
LT1054 • F05
OUT
OUT
voltage. For the basic configuration,
ground pin of the LT1054 must be less than the total of the
supply voltage minus the voltage loss due to the switches.
The voltage loss versus output current due to the switches
can be found in Typical Performance Characteristics. Other
configurations such as the negative doubler can provide
higher output voltages at reduced output currents (see
Typical Applications).
Capacitor Selection
For unregulated circuits the nominal values of C
should be equal. For regulated circuits see the section on
Regulation. While the exact values of C
noncritical, good quality, low ESR capacitors such as solid
tantalum are necessary to minimize voltage losses at high
currents. For C
be multiplied by four due to the fact that switch currents are
approximately two times higher than output current and
losses will occur on both the charge and discharge cycle.
This means that using a capacitor with 1 of ESR for C
will have the same effect as increasing the output imped-
ance of the LT1054 by 4 . This represents a significant
increase in the voltage losses. For C
less dramatic. C
at a current approximately equal to the output current and
the ESR of the capacitor will cause a step function to occur
in the output ripple at the switch transitions. This step
function will degrade the output regulation for changes in
output load current and should be avoided. Realizing that
large value tantalum capacitors can be expensive, a tech-
nique that can be used is to parallel a smaller tantalum
capacitor with a large aluminum electrolytic capacitor to
gain both low ESR and reasonable cost. Where physical
size is a concern some of the newer chip type surface
mount tantalum capacitors can be used. These capacitors
are normally rated at working voltages in the 10V to 20V
range and exhibit very low ESR (in the range of 0.1 ).
Output Ripple
The peak-to-peak output ripple is determined by the value
of the output capacitor and the output current. Peak-to-
peak output ripple may be approximated by the formula:
dV =
2fC
I
OUT
OUT
IN
OUT
the effect of the ESR of the capacitor will
is alternately charged and discharged
OUT
|
V
OUT
the affect of ESR is
IN
|
referred to the
and C
IN
and C
OUT
1054lfe
OUT
are
IN

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