LTC3221EDC-5#TRMPBF Linear Technology, LTC3221EDC-5#TRMPBF Datasheet - Page 9

IC SW CAP/DBLR 5V 60MA 6DFN

LTC3221EDC-5#TRMPBF

Manufacturer Part Number
LTC3221EDC-5#TRMPBF
Description
IC SW CAP/DBLR 5V 60MA 6DFN
Manufacturer
Linear Technology
Type
Switched Capacitor (Charge Pump), Doublerr
Datasheet

Specifications of LTC3221EDC-5#TRMPBF

Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
5V
Current - Output
60mA
Frequency - Switching
600kHz
Voltage - Input
2.7 ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
6-DFN
Operating Supply Voltage (min)
2.7V
Operating Supply Voltage (max)
5.5V
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Pin Count
6
Mounting
Surface Mount
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Lead Free Status / Rohs Status
Compliant

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APPLICATIO S I FOR ATIO
be expressed by the following equation:
where f
is the value of the fl ying capacitor. The charge pump will
typically be weaker than the theoretical limit due to ad-
ditional switch resistance. However, for very light load ap-
plications, the above expression can be used as a guideline
in determining a starting capacitor value.
Ceramic Capacitors
Capacitors of different materials lose their capacitance
with higher temperature and voltage at different rates.
For example, a ceramic capacitor made of X7R material
will retain most of its capacitance from –40°C to 85°C,
whereas, a Z5U or Y5V style capacitor will lose considerable
capacitance over that range. Z5U and Y5V capacitors may
also have a very strong voltage coeffi cient causing them
to lose 50% or more of their capacitance when the rated
voltage is applied. Therefore when comparing different
capacitors, it is often more appropriate to compare the
amount of achievable capacitance for a given case size
rather than discussing the specifi ed capacitance value.
For example, over rated voltage and temperature condi-
tions, a 1µF 10V Y5V ceramic capacitor in a 0603 case
may not provide any more capacitance than a 0.22µF 10V
X7R capacitor available in the same 0603 case. In fact,
for most LTC3221-3.3/LTC3221-5/LTC3221 applications,
these capacitors can be considered roughly equivalent. The
capacitor manufacturer’s data sheet should be consulted
to determine what value of capacitor is needed to ensure
0.6µF at all temperatures and voltages.
Table 1 shows a list of ceramic capacitor manufacturers
and how to contact them.
Table 1. Ceramic Capacitor Manufacturers
AVX
Kemet
Murata
Taiyo Yuden
Vishay
R
OL MIN
(
OSC
)
is the switching frequency (600kHz) and C
2
V
IN
I
OUT
U
V
OUT
U
www.avxcorp.com
www.kemet.com
www.murata.com
www.t-yuden.com
www.vishay.com
f
OSC
W
1
C
FLY
U
FLY
Programming the LTC3221 Output Voltage (FB Pin)
While the LTC3221-3.3/LTC3221-5 versions have internal
resistive dividers to program the output voltage, the pro-
grammable LTC3221 may be set to an arbitrary voltage via
an external resistive divider. Figure 3 shows the required
voltage divider connection.
The voltage divider ratio is given by the expression:
Since the LTC3221 employs a voltage doubling charge
pump, it is not possible to achieve output voltages greater
than twice the available input voltage. The V
range required for regulation is given by the following
expression:
Where R
I
than V
is poor. Also, V
operating voltage of 1.8V.
The sum of the voltage divider resistors can be made large
to keep the quiescent current to a minimum. Any standing
current in the output divider (given by 1.23/R2) will be
refl ected by a factor of 2 in the input current. A reasonable
resistance value should be such that the standing current
is in the range of 10µA to 100µA when V
OUT
Maximum V
whichever is higher
Minimum V
R
R
2
1
is the maximum load current. V
OUT
=
Figure 3. Programming the Adjustable LTC3221
OL
1 23
LTC3221-3.3/LTC3221-5
V
.
LTC3221
OUT
by more than 0.6V, or else the line regulation
is the effective open-loop output resistance and
V
V
IN
GND
IN
OUT
FB
IN
=
< V
1
6
3
4
has to be higher than the minimum
(
V
OUT
OUT
R1
R2
+ 0.6
+
I
OUT
2
3221 F03
C1
R
C
V
OUT
OUT
OL
IN
= 1.23V (1 +
LTC3221/
)
cannot be higher
or
OUT
1 8
.
is regulated.
R1
R2
V
IN
;
)
supply
9
3221f

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