LT1912EMSE#PBF Linear Technology, LT1912EMSE#PBF Datasheet - Page 12

• Manufacturer Part Number: LT1912EMSE#PBF
• Description: IC, STEP-DOWN REGULATOR, MSOP-10
• Manufacturer: Linear Technology

Specifications of LT1912EMSE#PBF

• Primary Input Voltage: 36V
• No. Of Outputs: 1
• Output Voltage: 20V
• Output Current: 2A
• No. Of Pins: 10
• Operating Temperature Range: -40°C To +125°C
• Supply Voltage Range: 3.6V To 36V
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 neces-
sary 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. Table 3 lists several Schottky diodes and their
manufacturers.
Table 3. Diode Vendors
LT1912
APPLICATIONS INFORMATION
Table 2. Capacitor Vendors
12
PART NUMBER
On Semicnductor
MBRM120E
MBRM140
Diodes Inc.
B220
B230
DFLS240L
International Rectifier
10BQ030
20BQ030
VENDOR
Panasonic
Kemet
Sanyo
Murata
AVX
Taiyo Yuden
I
D(AVG)
OUT
= I
is the output load current. The only reason to
OUT
PHONE
[phone]
[phone]
[phone]
[phone]
[phone]
(V
IN
(V)
– V
V
20
40
20
30
40
30
30
R
OUT
)/V
I
(A)
AVE
1
1
2
2
2
1
2
IN
V
F
(mV)
530
550
420
AT 1A
URL
www.panasonic.com
www.kemet.com
www.sanyovideo.com
www.murata.com
www.avxcorp.com
www.taiyo-yuden.com
V
F
(mV)
595
500
500
500
470
470
AT 2A
Ceramic Capacitors
A precaution regarding ceramic capacitors concerns the
maximum input voltage rating of the LT1912. A ceramic
input capacitor combined with trace or cable inductance
forms a high quality (under damped) tank circuit. If the
LT1912 circuit is plugged into a live supply, the input volt-
age can ring to twice its nominal value, possibly exceeding
the LT1912’s rating. This situation is easily avoided (see
the Hot Plugging Safely section).
Frequency Compensation
The LT1912 uses current mode control to regulate the
output. This simplifies loop compensation. In particular, the
LT1912 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 filter noise at the switching frequency, and is
required only if a phase-lead capacitor is used or if the
output capacitor has high ESR.
Loop compensation determines the stability and transient
performance. Designing the compensation network is a bit
complicated and the best values depend on the application
C
pin, as shown in Figure 2. Generally a capacitor (C
PART SERIES
Ceramic,
Polymer,
Tantalum
Ceramic,
Tantalum
Ceramic,
Polymer,
Tantalum
Ceramic
Ceramic,
Tantalum
Ceramic
F
) is not part of the loop compensation but
C
) in series to ground are used. In addi-
COMMANDS
EEF Series
T494, T495
POSCAP
TPS Series
1912fa
C
)