LTC3417AIFE#TRPBF Linear Technology, LTC3417AIFE#TRPBF Datasheet - Page 11

• Manufacturer Part Number: LTC3417AIFE#TRPBF
• Description: IC DC/DC CONV DUAL 20TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3417AIFE#TRPBF

• 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 ~ 85°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.
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
–
= I
–
OUT1
+I
+I
2
ΔI
OUT1
)/2. This simple worst case is commonly
ΔI
2
2
2
2
, the ripple is zero.
2
L1
)
)
L2
– V
= V
D 1– D
V
IN
(
OUT
OUT2
/2 = V
(
V
V
)
. The maximum typically oc-
IN
IN
OUT2
– V
RMS
OUT
or when V
.
)
IN
= 2V
OUT1
RMS
OUT2
OUT
= V
does not
1
, where
– V
OUT2
and I
IN
/2
=
2
Output Capacitor (C
The selection of C
ESR to minimize voltage ripple and load step transients.
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 avail-
able 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
ESR
OUT
V
OUT
L
COUT
O
) is determined by:
= ripple current in the inductor. The output ripple
= operating frequency, C
< 150mΩ
I
L
OUT1
ESR
OUT1
COUT
and C
and C
L
+
OUT2
= 0.35I
8 • f
OUT2
OUT
is driven by the required
O
OUT
1
• C
LOAD(MAX)
) Selection
LTC3417A
= output capacitance
have been met, the
OUT
, the output
L
IN
RIPPLE(P-P)
increases
and f
11
3417afb
O
=