LT1944-1EMS#TRPBF Linear Technology, LT1944-1EMS#TRPBF Datasheet - Page 6

• Manufacturer Part Number: LT1944-1EMS#TRPBF
• Description: IC DC/DC CONV STP-UP DUAL 10MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost)r

Specifications of LT1944-1EMS#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: 1.23 ~ 36 V
• Current - Output: 100mA, 175mA
• Voltage - Input: 1.2 ~ 15 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -

APPLICATIO S I FOR ATIO
LT1944-1
limited to 100mA (or 175mA), the power switch of the
LT1944-1 can handle larger currents without problem, but
the overall efficiency will suffer. Best results will be ob-
tained when I
Capacitor Selection
Low ESR (Equivalent Series Resistance) capacitors should
be used at the output to minimize the output ripple voltage.
Multilayer ceramic capacitors are the best choice, as they
have a very low ESR and are available in very small
packages. Their small size makes them a good companion
to the LT1944-1’s MS10 package. Solid tantalum capaci-
tors (like the AVX TPS, Sprague 593D families) or OS-CON
capacitors can be used, but they will occupy more board
area than a ceramic and will have a higher ESR. Always use
a capacitor with a sufficient voltage rating.
Ceramic capacitors also make a good choice for the input
decoupling capacitor, which should be placed as close as
possible to the LT1944-1. A 4.7 F input capacitor is
sufficient for most applications. Table 2 shows a list of
several capacitor manufacturers. Consult the manufactur-
ers for more detailed information and for their entire
selection of related parts.
Table 2. Recommended Capacitors
CAPACITOR TYPE
Ceramic
Ceramic
Ceramic
6
PEAK
is kept below 400mA for the LT1944-1.
U
U
VENDOR
Taiyo Yuden
[phone]
www.t-yuden.com
AVX
[phone]
www.avxcorp.com
Murata
[phone]
www.murata.com
W
U
Setting the Output Voltage
Set the output voltage for each switching regulator by
choosing the appropriate values for feedback resistors R1
and R2 (see Figure 1).
Diode Selection
For most LT1944-1 applications, the Philips BAT54 or
Central Semiconductor CMDSH-3 surface mount Schottky
diodes are an ideal choice. Schottky diodes, with their low
forward voltage drop and fast switching speed, are the
best match for the LT1944-1. Many different manufactur-
ers make equivalent parts, but make sure that the compo-
nent is rated to handle at least 100mA.
Lowering Output Voltage Ripple
Using low ESR capacitors will help minimize the output
ripple voltage, but proper selection of the inductor and the
output capacitor also plays a big role. The LT1944-1
provides energy to the load in bursts by ramping up the
inductor current, then delivering that current to the load.
If too large of an inductor value or too small of a capacitor
value is used, the output ripple voltage will increase
because the capacitor will be slightly overcharged each
burst cycle. To reduce the output ripple, increase the
output capacitor value or add a 4.7pF feed-forward capaci-
tor in the feedback network of the LT1944-1 (see the
circuits in the Typical Applications section). Adding this
small, inexpensive 4.7pF capacitor will greatly reduce the
output voltage ripple.
R
1
R
2
1 23
V
.
OUT
V
1