DataSheet.es    


PDF CDRH4D18-100 Data sheet ( Hoja de datos )

Número de pieza CDRH4D18-100
Descripción Dual Micropower DC/DC Converter with Positive and Negative Outputs
Fabricantes Linear Technology 
Logotipo Linear Technology Logotipo



Hay una vista previa y un enlace de descarga de CDRH4D18-100 (archivo pdf) en la parte inferior de esta página.


Total 8 Páginas

No Preview Available ! CDRH4D18-100 Hoja de datos, Descripción, Manual

FEATURES
s Generates Well-Regulated Positive and
Negative Outputs
s Low Quiescent Current:
20µA in Active Mode (per Converter)
<1µA in Shutdown Mode
s Operates with VIN as Low as 1.2V
s Low VCESAT Switch: 250mV at 300mA
s Uses Small Surface Mount Components
s High Output Voltage: Up to ±34V
s Tiny 10-Pin MSOP Package
U
APPLICATIO S
s Small TFT LCD Panels
s Handheld Computers
s Battery Backup
s Digital Cameras
LT1945
Dual Micropower DC/DC
Converter with Positive and
Negative Outputs
DESCRIPTIO
The LT®1945 is a dual micropower DC/DC converter in a
10-pin MSOP package. Each converter is designed with a
350mA current limit and an input voltage range of 1.2V to
15V, making the LT1945 ideal for a wide variety of appli-
cations. Both converters feature a quiescent current of
only 20µA at no load, which further reduces to 0.5µA in
shutdown. A current limited, fixed off-time control scheme
conserves operating current, resulting in high efficiency
over a broad range of load current. The 36V switch allows
high voltage outputs up to ±34V to be easily generated
without the use of costly transformers. The LT1945’s low
off-time of 400ns permits the use of tiny, low profile
inductors and capacitors to minimize footprint and cost in
space-conscious portable applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
2.7V
TO 5V
C1
4.7µF
Dual Output (+12V, –20V) Converter
L1
10µH
C4
0.1µF
D1
8 10
VIN
2
SHDN1
SW1
1
NFB1
LT1945
4
SHDN2
5
FB2
GND PGND PGND SW2
37 96
D2
100pF 365k
24.9k
–20V
10mA
C2
1µF
115k
L2
10µH
C1: TAIYO YUDEN JMK212BJ475
C2, C3: TAIYO YUDEN TMK316BJ105
C4: TAIYO YUDEN EMK107BJ104
D1, D2, D3: ZETEX ZHCS400
L1, L2: MURATA LQH3C100
4.7pF
D3
C3
1M 1µF
12V
20mA
1945 TA01
Efficiency at VIN = 3.6V
90
85
+12V OUTPUT
80
–20V OUTPUT
75
70
65
60
55
50
0.1
1 10
LOAD CURRENT (mA)
100
1945 TA01a
1945f
1

1 page




CDRH4D18-100 pdf
LT1945
APPLICATIO S I FOR ATIO
Choosing an Inductor
Several recommended inductors that work well with the
LT1945 are listed in Table 1, although there are many other
manufacturers and devices that can be used. Consult each
manufacturer for more detailed information and for their
entire selection of related parts. Many different sizes and
shapes are available. Use the equations and recommenda-
tions in the next few sections to find the correct inductance
value for your design.
Table 1. Recommended Inductors
PART
VALUE (µH) MAX DCR ()
LQH3C4R7 4.7 0.26
LQH3C100 10 0.30
LQH3C220 22 0.92
CD43-4R7
CD43-100
CDRH4D18-4R7
CDRH4D18-100
4.7
10
4.7
10
0.11
0.18
0.16
0.20
DO1608-472
DO1608-103
DO1608-223
4.7
10
22
0.09
0.16
0.37
VENDOR
Murata
(714) 852-2001
www.murata.com
Sumida
(847) 956-0666
www.sumida.com
Coilcraft
(847) 639-6400
www.coilcraft.com
Inductor Selection—Boost Regulator
The formula below calculates the appropriate inductor
value to be used for a boost regulator using the LT1945 (or
at least provides a good starting point). This value pro-
vides a good tradeoff in inductor size and system perfor-
mance. Pick a standard inductor close to this value. A
larger value can be used to slightly increase the available
output current, but limit it to around twice the value
calculated below, as too large of an inductance will in-
crease the output voltage ripple without providing much
additional output current. A smaller value can be used
(especially for systems with output voltages greater than
12V) to give a smaller physical size. Inductance can be
calculated as:
( )VOUT VIN MIN + VD
L = ILIM tOFF
where VD = 0.4V (Schottky diode voltage), ILIM = 350mA
and tOFF = 400ns; for designs with varying VIN such as
battery powered applications, use the minimum VIN value
in the above equation. For most regulators with output
voltages below 7V, a 4.7µH inductor is the best choice,
even though the equation above might specify a smaller
value. This is due to the inductor current overshoot that
occurs when very small inductor values are used (see
Current Limit Overshoot section).
For higher output voltages, the formula above will give
large inductance values. For a 2V to 20V converter (typical
LCD Bias application), a 21µH inductor is called for with
the above equation, but a 10µH inductor could be used
without excessive reduction in maximum output current.
Inductor Selection—SEPIC Regulator
The formula below calculates the approximate inductor
value to be used for a SEPIC regulator using the LT1945.
As for the boost inductor selection, a larger or smaller
value can be used.
L
=
2
VOUT +
ILIM
VD

tOFF
Inductor Selection—Inverting Regulator
The formula below calculates the appropriate inductor
value to be used for an inverting regulator using the
LT1945 (or at least provides a good starting point). This
value provides a good tradeoff in inductor size and system
performance. Pick a standard inductor close to this value
(both inductors should be the same value). A larger value
can be used to slightly increase the available output
current, but limit it to around twice the value calculated
below, as too large of an inductance will increase the
output voltage ripple without providing much additional
output current. A smaller value can be used (especially for
systems with output voltages greater than 12V) to give a
smaller physical size. Inductance can be calculated as:
VOUT + VD
L = 2 ILIM
 tOFF
where VD = 0.4V (Schottky diode voltage), ILIM = 350mA
and tOFF = 400ns.
1945f
5

5 Page










PáginasTotal 8 Páginas
PDF Descargar[ Datasheet CDRH4D18-100.PDF ]




Hoja de datos destacado

Número de piezaDescripciónFabricantes
CDRH4D18-100Dual Micropower DC/DC Converter with Positive and Negative OutputsLinear Technology
Linear Technology

Número de piezaDescripciónFabricantes
SLA6805M

High Voltage 3 phase Motor Driver IC.

Sanken
Sanken
SDC1742

12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters.

Analog Devices
Analog Devices


DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares,
permitiéndote verlos en linea o descargarlos en PDF.


DataSheet.es    |   2020   |  Privacy Policy  |  Contacto  |  Buscar