LT3980EDE#TRPBF Linear Technology, LT3980EDE#TRPBF Datasheet - Page 12

• Manufacturer Part Number: LT3980EDE#TRPBF
• Description: IC SWITCHING REG STP-DN 2A 14DFN
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT3980EDE#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.79 ~ 52.2 V
• Current - Output: 2A
• Frequency - Switching: 100kHz ~ 2.4MHz
• Voltage - Input: 3.6 ~ 58 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

APPLICATIONS INFORMATION
LT3980
Low ESR is important, so choose one that is intended for
use in switching regulators. The ESR should be specifi ed
by the supplier, and should be 0.05Ω or less. Such a
capacitor will be larger than a ceramic capacitor and will
have a larger capacitance, because the capacitor must be
large to achieve low ESR. Table 2 lists several capacitor
vendors.
Table 2. Capacitor Vendors
VENDOR
Panasonic
Kemet
Sanyo
Murata
AVX
Taiyo Yuden www.taiyo-yuden.com Ceramic
Catch Diode
The catch diode conducts current only during switch off
time. Average forward current in normal operation can
be calculated from:
where I
consider a diode with a larger current rating than necessary
for nominal operation is for the worst-case condition of
shorted output. The diode current will then increase to the
typical peak switch current. Peak reverse voltage is equal
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 LT3980 will keep the
switch off when V
rated Schottky even when V
Ceramic Capacitors
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT3980 due to their piezoelectric
nature. When in Burst Mode operation, the LT3980’s
12
I
D(AVG)
OUT
= I
www.panasonic.com
www.kemet.com
www.sanyovideo.com Ceramic, Polymer,
www.murata.com
www.avxcorp.com
is the output load current. The only reason to
OUT
(V
URL
IN
IN
> 64V which allows the use of 64V
– V
OUT
IN
)/V
Ceramic, Polymer,
Tantalum
Ceramic, Tantalum T494, T495
Tantalum
Ceramic
Ceramic, Tantalum SOT-23
ranges up to 80V.
IN
PART SERIES
EEF Series
POSCAP
SOT-23
TPS Series
COMMANDS
switching frequency depends on the load current, and at
very light loads the LT3980 can excite the ceramic capaci-
tor at audio frequencies, generating audible noise. Since
the LT3980 operates at a lower current limit during Burst
Mode operation, the noise is nearly silent to a casual ear.
If this is unacceptable, use a high performance tantalum
or electrolytic capacitor at the output.
Frequency Compensation
The LT3980 uses current mode control to regulate the
output. This simplifi es loop compensation. In particular,
the LT3980 does not require the ESR of the output capacitor
for stability, so you are free to use ceramic capacitors to
achieve low output ripple and small circuit size. Frequency
compensation is provided by the components tied to the
V
and a resistor (R
tion, there may be lower value capacitor in parallel. This
capacitor (C
is used to fi lter noise at the switching frequency, and is
required only if a phase-lead capacitor is used or if the
output capacitor has high ESR.
C
LT3980
pin, as shown in Figure 2. Generally a capacitor (C
CURRENT MODE
POWER STAGE
g
m
C
F
= 5.3mho
V
R
C
C
3M
C
F
C
Figure 2. Model for Loop Response
) is not part of the loop compensation but
500μmho
C
) in series to ground are used. In addi-
g
AMPLIFIER
m
ERROR
=
–
+
GND
0.79V
SW
FB
R2
R1
TANTALUM
POLYMER
C
PL
ESR
C1
OR
+
3980 F02
OUTPUT
C1
CERAMIC
3980f
C
)