LT3663EMS8E-5#PBF Linear Technology, LT3663EMS8E-5#PBF Datasheet - Page 9

• Manufacturer Part Number: LT3663EMS8E-5#PBF
• Description: IC BUCK 5V 1.2A 8MSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT3663EMS8E-5#PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 5V
• Current - Output: 1.2A
• Frequency - Switching: 1MHz
• Voltage - Input: 7.5 ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP Exposed Pad, 8-HMSOP, 8-eMSOP
• Primary Input Voltage: 36V
• No. Of Outputs: 1
• Output Voltage: 5V
• Output Current: 1.2A
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Switching Frequency Max: 1.65MHz
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS INFORMATION
Catch Diode
The catch diode conducts current only during switch-off
time. Average forward current in normal operation is
calculated from:
where I
grammed by the I
to the regulator input voltage. Use a Schottky diode with a
reverse voltage rating greater than the input voltage. The
overvoltage protection feature in the LT3663 keeps the
switch off when V
45V rated Schottky even when V
Input Capacitor
Bypass the input of the LT3663 circuit with a 1μF or higher
value ceramic capacitor of X7R or X5R type. Y5V types
have poor performance over temperature and applied volt-
age and are not recommended. If the input power source
has high impedance, or there is signifi cant inductance
due to long wires or cables, additional bulk capacitance
may be necessary. This can be provided with a low per-
formance electrolytic capacitor. Step-down regulators
draw current from the input supply in pulses with very
fast rise and fall times. The input capacitor is required
to reduce the resulting voltage ripple at the LT3663 and
to force this very high frequency switching current into
a tight local loop, minimizing EMI. Place the capacitor in
close proximity to the LT3663 and the catch diode; (see
the PCB Layout section).
Output Capacitor
A 10μF or greater ceramic capacitor is recommended to
provide low output ripple and good transient response.
Ceramic capacitors have very low equivalent series re-
sistance (ESR) and provide the best ripple performance.
I
D AVG
(
OUT
)
=
I
is the maximum output load current pro-
OUT
LIM
V
IN
IN
resistor. Peak reverse voltage is equal
> 39V (typical) allowing the use of a
–
V
IN
V
OUT
IN
ranges up to 60V.
Use X5R or X7R types and keep in mind that a ceramic
capacitor biased with V
nominal capacitance.
High performance electrolytic capacitors can be used for
the output capacitor. Low ESR is important, so choose
one that is intended for use in switching regulators. Keep
the ESR less than 0.1Ω.
I
The LT3663 output current limit controls the maximum
current delivered from the LT3663 regulator. This allows
tighter control of the system power dissipation and also
protects the inductor and diode from overheating during
an overload or short circuit condition. A resistor con-
nected from I
Table 1 details the I
current limits.
Table 1. Output Current Limit vs R
There may be a reason in some applications to move the
output current limit. The following simple circuit demon-
strates how the output current limit can be adjusted:
LIM
Figure 3. Circuit for Multiple Values of Output Current Limit
OUTPUT CURRENT LIMIT (A)
Resistor
OFF , R
ON, R
ILIM
= RA + RB
ILIM
0.4
0.6
0.8
1.0
1.2
LIM
= RA
pin to GND programs the output current.
LIM
resistor values for specifi c output
OUT
RA
RB
has less than its specifi ed
LIM
Value
I
LIM
R
ILIM
LT3663
VALUE (kΩ)
48.7
36.5
28.7
140
75
LT3663
3663 F03
3663fb
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