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PDF TC126 Data sheet ( Hoja de datos )

Número de pieza TC126
Descripción (TC125) PFM Step-Up DC/DC Regulators
Fabricantes Microchip Technology 
Logotipo Microchip Technology Logotipo



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TC125/TC126
PFM Step-Up DC/DC Regulators
Features
• Assured Start-up at 0.9V
• PFM (100kHz Max Operating Frequency)
• 40µA Maximum Supply Current
(VOUT = 3V @ 30mA)
• 0.5µA Shutdown Mode (TC125)
• Voltage Sense Input (TC126)
• Requires Only Three External Components
• 80mA Maximum Output Current
• Small Package: 5-Pin SOT-23A
Applications
• Palmtops/PDAs
• Battery-Operated Systems
• Cameras
• Portable Communicators
Device Selection Table
Part
Number
Output
Voltage
(V)*
Package
Operating
Temp.
Range
TC125501ECT 5.0 5-Pin SOT-23A -40°C to +85°C
TC125331ECT 3.3 5-Pin SOT-23A -40°C to +85°C
TC125301ECT 3.0 5-Pin SOT-23A -40°C to +85°C
TC126503ECT 5.0 5-Pin SOT-23A -40°C to +85°C
TC126333ECT 3.3 5-Pin SOT-23A -40°C to +85°C
TC126303ECT 3.0 5-Pin SOT-23A -40°C to +85°C
*Other output voltages are available. Please contact
Microchip Technology Inc. for details.
Package Type
5-Pin SOT-23A
LX
GND
LX
GND
5 45 4
TC125
TC126
1
SHDN
2
PS
3
NC
12
SENSE VDD
3
NC
NOTE: 5-Pin SOT-23A is equivalent to the EIAJ SC-74A
General Description
The TC125/126 step-up (Boost) switching regulators
furnish output currents to a maximum of 80mA
(VIN = 2V, VOUT = 3V) with typical efficiencies above
80%. These devices employ pulse frequency modula-
tion (PFM) for minimum supply current at low loads.
They are ideal for battery-operated applications
powered from one or more cells. Maximum supply
current is less than 70µA at full output load, and less
than 5µA in standby (VOUT = 3V). Both devices require
only an external inductor, diode, and capacitor to
implement a complete DC/DC regulator.
The TC126 has separate output voltage sensing and
chip power inputs for greater application flexibility. The
TC125 combines the output voltage sensing and chip
power inputs onto a single package pin, but adds a
power-saving shutdown mode that suspends regulator
operation and reduces supply current to less than
0.5µA when the shutdown control input (SHDN) is low.
The TC125/TC126 are available in a small 5-Pin
SOT-23A package, occupy minimum board space and
use small external components. The TC125 accepts
input voltages from 2V to 10V. The TC126 accepts
input voltages from 2.2V to 10V. Both the TC125 and
TC126 have a start-up voltage of 0.9V at light load.
Typical Application
Sumida
100µH CD54
VIN
MA735
2 x "AA"
Cell
+
3V
54
LX GND
TC125
SHDN PS
12
NC
3
VOUT
5V @80mA
+
47µF/16V
Tantalum
Two Cell to 5V Boost Regulator
© 2002 Microchip Technology Inc.
DS21372B-page 1

1 page




TC126 pdf
TC125/TC126
4.0 APPLICATIONS
4.1 Input Bypass Capacitors
Adding an input bypass capacitor reduces peak current
transients drawn from the input supply and reduces the
switching noise generated by the regulator. The source
impedance of the input supply determines the size of
the capacitor that should be used.
4.2 Inductor Selection
Selecting the proper inductor value is a trade-off
between physical size and power conversion require-
ments. Lower value inductors cost less, but result in
higher ripple current and core losses. They are also
more prone to saturate since the coil current ramps to
a higher value. Larger inductor values reduce both
ripple current and core losses, but are larger in physical
size and tend to increase the start-up time slightly. The
recommended inductor value for use with the TC125/
126 is 100µH. Inductors with a ferrite core (or equiva-
lent) are recommended. For highest efficiency, use an
inductor with a series resistance less than 20m.
4.3 Internal Transistor Switch Current
Limiting
The peak switch current is equal to the input voltage
divided by the RDSON of the internal switch. The
internal transistor has absolute maximum current rating
of 400mA with a design limit of 350mA. A built-in
oscillator frequency doubling circuit guards against
high switching currents. Should the voltage on the LX
pin rise above 1.1V, max while the internal N-channel
switch is ON, the oscillator frequency automatically
doubles to minimize ON time. Although reduced, switch
current still flows because the regulator remains in
operation. Therefore, the LX input is not internally
current limited and care must be taken never to exceed
the 350mA maximum limit. Failure to observe this will
result in damage to the regulator.
4.4 Output Diode
For best results, use a Schottky diode such as the
MA735, 1N5817, MBR0520L or equivalent. Connect
the diode between the PS and LX pins (TC125) or
SENSE and LX pins (TC126) as close to the IC as
possible. (Do not use ordinary rectifier diodes since the
higher threshold voltages reduce efficiency.)
4.5 Output Capacitor
The effective series resistance of the output capacitor
directly affects the amplitude of the output voltage
ripple. (The product of the peak inductor current and
the ESR determines output ripple amplitude.) There-
fore, a capacitor with the lowest possible ESR should
be selected. Smaller capacitors are acceptable for light
loads or in applications where ripple is not a concern.
The Sprague 595D series of tantalum capacitors are
among the smallest of all low ESR surface mount
capacitors available. Table 4-1 lists suggested
components and suppliers.
4.6 Board Layout Guidelines
As with all inductive switching regulators, the TC125/
126 generate fast switching waveforms that radiate
noise. Interconnecting lead lengths should be
minimized to keep stray capacitance, trace resistance,
and radiated noise as low as possible. In addition, the
GND pin, input bypass capacitor, and output filter
capacitor ground leads should be connected to a single
point. The input capacitor should be placed as close to
power and ground pins of the TC125/126 as possible.
TABLE 4-1: SUGGESTED COMPONENTS AND SUPPLIERS
Type
Surface Mount
Through-Hole
Inductors
Sumida
CD54 Series
CDR125 Series
Coiltronics
CTX Series
Murata
LQN6C Series
Sumida
RCH855 Series
RCH110 Series
Renco
RL1284-12
Capacitors
Matsuo
267 Series
Murata
GRM200 Series
Sprague
595D Series
Nichicon
F93 Series
Sanyo
OS-CON Series
Nichicon
PL Series
Diodes
Nihon
EC10 Series
Matsushita
MA735 Series
ON Semiconductor
1N5817 - 1N5822
© 2002 Microchip Technology Inc.
DS21372B-page 5

5 Page





TC126 arduino
TC125/TC126
Information contained in this publication regarding device
applications and the like is intended through suggestion only
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
No representation or warranty is given and no liability is
assumed by Microchip Technology Incorporated with respect
to the accuracy or use of such information, or infringement of
patents or other intellectual property rights arising from such
use or otherwise. Use of Microchip’s products as critical com-
ponents in life support systems is not authorized except with
express written approval by Microchip. No licenses are con-
veyed, implicitly or otherwise, under any intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, FilterLab,
KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER,
PICSTART, PRO MATE, SEEVAL and The Embedded Control
Solutions Company are registered trademarks of Microchip Tech-
nology Incorporated in the U.S.A. and other countries.
dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,
In-Circuit Serial Programming, ICSP, ICEPIC, microPort,
Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM,
MXDEV, MXLAB, PICC, PICDEM, PICDEM.net, rfPIC, Select
Mode and Total Endurance are trademarks of Microchip
Technology Incorporated in the U.S.A.
Serialized Quick Turn Programming (SQTP) is a service mark
of Microchip Technology Incorporated in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2002, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
© 2002 Microchip Technology Inc.
Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and Tempe, Arizona in July 1999
and Mountain View, California in March 2002.
The Company’s quality system processes and
procedures are QS-9000 compliant for its
PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals,
non-volatile memory and analog products. In
addition, Microchip’s quality system for the
design and manufacture of development
systems is ISO 9001 certified.
DS2372B-page 11

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