LT1945EMS Linear Technology, LT1945EMS Datasheet - Page 7

• Manufacturer Part Number: LT1945EMS
• Description: IC DC/DC CONV MICRPWR DUAL10MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost), Inverting, Flyback, Sepicr

Specifications of LT1945EMS

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: 1.23 ~ 36 V
• Current - Output: 350mA
• 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: Contains lead / RoHS non-compliant
• Power - Output: -
• Frequency - Switching: -

APPLICATIONS INFORMATION
of related parts.
Table 2. Recommended Capacitors
CAPACITOR TYPE
Ceramic
Ceramic
Ceramic
Setting the Output Voltages
Set the output voltage for Switcher 1 (negative output
voltage ) by choosing the appropriate values for feedback
resistors R1 and R2.
Set the output voltage for Switcher 2 (positive output
voltage) by choosing the appropriate values for feedback
resistors R1B and R2B (see Figure 1).
PACKAGE DESCRIPTION
R
R
1
1
=
=
R
1 23
2
.
R
(.0120 .0015)
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.305 0.038
V
⎛
⎝ ⎜
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
2
OUT
V
V
1 23
TYP
OUT
.
(.206)
+
5.23
MIN
– .
(
RECOMMENDED SOLDER PAD LAYOUT
2 10
1 23
−
•
1
⎞
⎠ ⎟
V
−
6
)
VENDOR
Taiyo Yuden
[phone]
www.t-yuden.com
AVX
[phone]
www.avxcorp.com
Murata
[phone]
www.murata.com
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
0.889 0.127
(.035 .005)
(.126 – .136)
3.2 – 3.45
(.0197)
0.50
BSC
GAUGE PLANE
(Reference LTC DWG # 05-08-1661)
(.007)
0.18
10-Lead Plastic MSOP
0.254
(.010)
MS Package
DETAIL “A”
DETAIL “A”
Diode Selection
For most LT1945 applications, the Zetex ZHCS400 sur-
face mount Schottky diode (0.4A, 40V) is an ideal choice.
Schottky diodes, with their low forward voltage drop and
fast switching speed, are the best match for the LT1945.
The Motorola MBR0520, MBR0530, or MBR0540 can also
be used. Many different manufacturers make equivalent
parts, but make sure that the component is rated to handle
at least 0.35A.
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 LT1945 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 capacitor in the feedback
network of the LT1945 (see the circuits in the Typical Ap-
plications section). Adding this small, inexpensive 4.7pF
capacitor will greatly reduce the output voltage ripple.
0 – 6 TYP
(.021 .006)
0.53 0.01
SEATING
PLANE
3.00 0.102
(.118 .004)
(.007 – .011)
(.192 .004)
0.17 – 0.27
(NOTE 3)
4.88 0.10
(.043)
MAX
1.10
(.0197)
0.50
10
TYP
1 2 3 4 5
9
8
7 6
(.118 .004)
3.00 0.102
(.0196 .003)
0.497 0.076
(.034)
0.86
NOTE 4
REF
(.005 .002)
0.13 0.05
MSOP (MS) 0402
REF
LT1945
1945fa
7