LTC3417AIFE-1#PBF Linear Technology, LTC3417AIFE-1#PBF Datasheet - Page 11

• Manufacturer Part Number: LTC3417AIFE-1#PBF
• Description: IC BUCK SYNC ADJ 1A/1.5A 20TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3417AIFE-1#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 5 V
• Current - Output: 1A, 1.5A
• Frequency - Switching: 1.5MHz, 0.6MHz ~ 4MHz
• Voltage - Input: 2.25 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS INFORMATION
When D1 = D2 then the equation simplifi es to:
or
where the maximum average output currents I
equal the respective peak currents minus half the peak-
to-peak ripple currents:
These formula have a maximum at V
I
used to determine the highest I
For “out of phase” operation, the ripple current can be
lower than the “in phase” current.
In the “out of phase” case, the maximum I
occur when V
curs when V
= V
case ripple is about 75% of the worst case ripple in the
“in phase” mode. Also note that when V
V
Note that capacitor manufacturer’s ripple current ratings
are often based on only 2000 hours lifetime. This makes
it advisable to further derate the capacitor, or choose a
capacitor rated at a higher temperature than required.
Several capacitors may also be paralleled to meet the
size or height requirements of the design. An additional
0.1μF to 1μF ceramic capacitor is also recommended on
V
ceramic capacitor solution.
Output Capacitor (C
The selection of C
ESR to minimize voltage ripple and load step transients.
RMS
IN
IN
I
I
I
I
/2 and I
RMS
RMS
1
OUT1
2
for high frequency decoupling, when not using an all
=I
=I
= (I
LIM1
LIM2
. As a good rule of thumb, the amount of worst
= I
= I
1
(
(
+ I
1
1
1
–
–
OUT1
= I
+I
+I
2
ΔI
OUT1
)/2. This simple worst case is commonly
ΔI
2
2
2
2
, the ripple is zero.
2
L1
)
)
L2
OUT1
– V
= V
D 1– D
V
OUT1
IN
(
OUT
and C
/2 = V
OUT2
(
and C
V
V
)
. The maximum typically oc-
IN
IN
OUT2
OUT2
– V
OUT2
RMS
is driven by the required
OUT
or when V
.
) Selection
)
IN
= 2V
OUT1
RMS
OUT2
OUT
= V
does not
1
, where
– V
OUT2
and I
IN
/2
=
2
Typically, once the ESR requirement is satisfi ed, the
capacitance is adequate for fi ltering. The output ripple
(ΔV
where f
and ΔI
is highest at maximum input voltage, since ΔI
with input voltage. With ΔI
ripple will be less than 100mV at maximum V
1MHz with:
Once the ESR requirements for C
RMS current rating generally far exceeds the I
requirement, except for an all ceramic solution.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the capacitance, ESR or RMS
current handling requirement of the application. Aluminum
electrolytic, special polymer, ceramic and dry tantalum
capacitors are all available in surface mount packages. The
OS-CON semiconductor dielectric capacitor available from
Sanyo has the lowest ESR(size) product of any aluminum
electrolytic at a somewhat higher price. Special polymer
capacitors, such as Sanyo POSCAP , offer very low ESR, but
have a lower capacitance density than other types. Tantalum
capacitors have the highest capacitance density, but it has
a larger ESR and it is critical that the capacitors are surge
tested for use in switching power supplies. An excellent
choice is the AVX TPS series of surface tantalums, available
in case heights ranging from 2mm to 4mm. Aluminum
electrolytic capacitors have a signifi cantly larger ESR, and
are often used in extremely cost-sensitive applications
provided that consideration is given to ripple current
ratings and long term reliability. Ceramic capacitors have
the lowest ESR and cost but also have the lowest capaci-
tance density, high voltage and temperature coeffi cient
and exhibit audible piezoelectric effects. In addition, the
high Q of ceramic capacitors along with trace inductance
can lead to signifi cant ringing. Other capacitor types
include the Panasonic specialty polymer (SP) capacitors.
ESR
OUT
V
OUT
L
COUT
O
) is determined by:
= ripple current in the inductor. The output ripple
= operating frequency, C
< 150mΩ
I
L
ESR
COUT
L
+
= 0.35I
8 • f
LTC3417A-1
OUT
O
OUT
1
• C
LOAD(MAX)
= output capacitance
have been met, the
OUT
, the output
L
IN
RIPPLE(P-P)
increases
and f
11
3417a1fa
O
=