PFM/PWM Step-Down DC/DC Controller 57µA (Typ) Supply Current Outp

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PFM/PWM Step-Down DC/DC Controller 57µA (Typ) Supply Current Outp

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TC105
PFM/PWM Step-Down DC/DC Controller
57µA (Typ) Supply Current Output Current 0.5µA Shutdown Mode 300kHz Switching Frequency Small Inductor Size Programmable Soft-Start Typical Efficiency Small Package: 5-Pin SOT-23A
Package Type
5-Pin SOT-23A
VOUT SHDN
TC105
Applications
Palmtops Battery-Operated Systems Portable Instruments Positive Bias Generators Portable Communicators Hand-Held Scanners Down Converters
NOTE: 5-Pin SOT-23A equivalent EIAJ SC-74A
General Description
TC105 step-down (Buck) switching controller that furnishes output currents (max) while delivering typical efficiency 92%. TC105 normally operates pulse width modulation mode (PWM), automatically switches pulse frequency modulation (PFM) output loads greater efficiency. Oscillator frequency 300kHz, allowing small (22µH) inductors. Supply current draw only 102µA (max), reduced less than 0.5µA when SHDN input brought low. Regulator operation suspended during shutdown. TC105 accepts maximum input voltage 10V. TC105 available small 5-Pin SOT-23A package, occupies minimum board space ideal wide range applications.
Device Selection Table
Part Number
TC105503ECT TC105333ECT TC105303ECT
Output Voltage (V)*
Package
5-Pin SOT-23A 5-Pin SOT-23A 5-Pin SOT-23A
Osc. Freq. (kHz)
Operating Temp. Range
-40°C +85°C -40°C +85°C -40°C +85°C
*Other output voltages available. Please contact Microchip Technology Inc. details.
Functional Block Diagram
22µH (Sumida CD54) 470K MA737 0.033µF 3.3V VOUT
(From System Control Logic)
VOUT
SHDN
47µF Tantalum
TC105333ECT
9430 VBATT NiMH
10µF/16V
3.3V Regulated Supply Using NiMH Battery Pack Input
2002 Microchip Technology Inc.
DS21349B-page
TC105
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings*
Voltage -0.3V +12V Output Current .±100mA Voltage VOUT, EXT, SHDN Pins .-0.3V +0.3V Power Dissipation.150mW Operating Temperature Range. -40°C +85°C Storage Temperature Range -40°C +125°C
*Stresses above those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only functional operation device these other conditions above those indicated operation sections specifications implied. Exposure Absolute Maximum Rating conditions extended periods affect device reliability.
TC105 ELECTRICAL SPECIFICATIONS
Electrical Characteristics: Note fOSC kHz; 25°C, unless otherwise noted. Symbol ISTBY ISHDN fOSC VOUT Parameter Operating Supply Voltage Minimum Input Voltage Operating Supply Current Standby Supply Current Shutdown Supply Current Oscillator Frequency Output Voltage 0.975 0.65 10.0 1.025 0.20 IOUT VOUT external components VOUT external components external components; 3.0V 3.3V 5.0V VOUT SHDN VEXT (VIN 0.4V) external components; 3.0V 3.3V 5.0V VOUT SHDN VIN, VEXT 0.4V Units High; external components; VOUT SHDN external components; 3.0V, 3.3V VOUT SHDN 5.0V external components; 3.0V, 3.3V VOUT SHDN 5.0V SHDN VOUT 0.3V Note Test Conditions
DTYMAX Maximum Duty Cycle (PWM Mode) DTYPFM Duty Cycle (PFM Mode) REXTH SHDN Input Logic High SHDN Input Logic Resistance
REXTL
Resistance
Note
Efficiency
3.0V, 4.5V, IOUT 200mA 3.3V, 5.0V, IOUT 220mA 5.0V, 7.5V, IOUT 320mA factory output voltage setting.
DS21349B-page
2002 Microchip Technology Inc.
TC105
DESCRIPTIONS
descriptions pins listed Table 2-1.
TABLE 2-1:
(5-Pin SOT-23A)
FUNCTION TABLE
Symbol SHDN Description Switch transistor control output. This terminal connects gate external P-channel MOSFET base external transistor through current limiting resistor). Power supply voltage input. Ground terminal. Shutdown input (active low). device enters power shutdown state when this input brought low. During shutdown, regulator action suspended, supply current reduced less than 0.5µA. device resumes normal operation when SHDN again brought high. Voltage sense input. This input senses output voltage regulation must connected output voltage node shown application schematic this data sheet.
VOUT
2002 Microchip Technology Inc.
DS21349B-page
TC105
DETAILED DESCRIPTION
Input Bypass Capacitors
TC105 PFM/PWM step-down DC/DC controller systems operating from more cells, line-powered applications. uses primary modulation scheme, automatically converts output duty cycles less than approximately 10%. conversion provides reduced supply current, therefore higher operating efficiency loads. TC105 uses external switching transistor, allowing construction switching regulators with output currents TC105 consumes only 102µA, max, supply current when VOUT 3.3V, placed 0.5µA shutdown mode bringing shutdown input (SHDN) low. regulator remains disabled while shutdown mode, output voltage discharges zero through load. Normal operation resumes when SHDN brought high. Other features include built-in undervoltage lockout (UVLO) externally programmable soft start time. Using input bypass capacitor reduces peak current transients drawn from input supply reduces switching noise generated regulator. source impedance input supply determines size capacitor that should used.
Output Capacitor
effective series resistance output capacitor directly affects amplitude output voltage ripple. (The product peak inductor current determines output ripple amplitude.) Therefore, capacitor with lowest possible should selected. Smaller capacitors acceptable light loads applications where ripple concern. Sprague 595D series tantalum capacitors among smallest surface mount capacitors available. Table lists suggested components suppliers.
Power Shutdown Mode
Inductor Selection
TC105 enters power shutdown mode when SHDN brought low. While shutdown, oscillator disabled output switch shut off. Normal regulator operation resumes when SHDN again brought high. SHDN tied input supply used.
Soft Start
Soft start allows output voltage gradually ramp from rated output value during start-up. This action minimizes eliminates) overshoot, general, reduces stress circuit components. Figure shows circuit required implement soft start (values 470K 0.033µF respectively, adequate most applications).
Selecting proper inductor value trade-off between physical size power conversion requirements. Lower value inductors cost less, result higher ripple current core losses. They also more prone saturate since coil current ramps faster could overshoot desired peak value. This only reduces efficiency, could also cause current rating external components exceeded. Larger inductor values reduce both ripple current core losses, larger physical size tend increase start-up time slightly. 22µH inductor recommended best overall compromise. highest efficiency, inductors with resistance (less than minimize radiated noise, consider using toroid, core shielded-bobbin inductor.
Undervoltage Lockout (UVLO)
Output Diode
TC105 disabled when below undervoltage lockout threshold. This threshold equal guaranteed minimum operating voltage TC105 (i.e., 2.2V). When UVLO active, TC105 completely disabled.
high operating frequency TC105 requires high-speed diode. Schottky diodes such MA737 1N5817 through 1N5823 (and equivalent surface mount versions) recommended. Select diode whose average current rating greater than peak inductor current whose voltage rating higher than VDDMAX.
DS21349B-page
2002 Microchip Technology Inc.
TC105
External Switching Transistor Selection
3.8.1 BOARD LAYOUT GUIDELINES
with inductive switching regulators, TC105 generates fast switching waveforms, which radiate noise. Interconnecting lead lengths should minimized keep stray capacitance, trace resistance radiated noise possible. addition, pin, input bypass capacitor output filter capacitor ground leads should connected single point. input capacitor should placed close power ground pins TC105 possible. length trace must also kept short possible.
complementary output with maximum resistance when high ground when low. designed directly drive P-channel MOSFET bipolar transistor through base current limiting resistor (Figure 4-2). transistor recommended applications where less than 2.5V. Otherwise, P-channel MOSFET preferred affords highest efficiency because does draw gate drive current. However, P-channel MOSFETs typically more expensive than bipolar transistors. P-channel MOSFET selection determined mainly on-resistance, gate-source threshold, gate charge requirements. Also, drain-to-source gate-to-source breakdown voltage ratings must greater than VDDMAX. total gate charge specification should less than 100nC best efficiency. MOSFET must capable handling required peak inductor current, should have very on-resistance that current. example, Si9430 MOSFET drain-to-source rating -20V, typical on-resistance rDSON 0.07 with -4.5V. Table lists suppliers external components recommended with TC105.
2002 Microchip Technology Inc.
DS21349B-page
TC105
APPLICATIONS
Circuit Examples
FIGURE 4-1:
SOFT START CIRCUIT
470K
SHDN/SS
Figure shows TC105 using switching transistor (Zetex FZT749) that VCESAT Other high beta transistors used, values need adjustment significantly different from that FZT749. circuit Figure utilizes P-channel MOSFET switching transistor (Silconix Si9430). This transistor member Littlefootfamily small outline MOSFETs.
0.033µF
TC105
Shutdown Used
470K SHDN 0.033µF (From System Control Logic)
SHDN/SS
TC105
Shutdown Used
FIGURE 4-2:
EXTERNAL TRANSISTOR CONNECTION
VOUT VOUT
TC105
TC105
P-Channel MOSFET
Bipolar Transistor
DS21349B-page
2002 Microchip Technology Inc.
TC105
FIGURE 4-3: REGULATOR USING TRANSISTOR
FZ749 10µF 22µH Sumida CD-54
2.5V
MA737
47µF Tantalum
VOUT 1.8V 470K
VOUT 2200
SHDN/SS
0.033µF
TC105
FIGURE 4-4:
REGULATOR USING P-CHANNEL MOSFET
Si9430 10µF 22µH Sumida CD-54
MA737
47µF Tantalum
VOUT 470K 0.033µF
VOUT SHDN/SS
TC105
TABLE 4-1:
Type Surface Mount
SUGGESTED COMPONENTS SUPPLIERS
Inductors Sumida CD54 Series CDRH Series Coilcraft Series Capacitors Series Sprague 595D Series Diodes Semiconductor MBRS340T3 Nihon Series Matsushita MA737 Sanyo OS-CON Series Nichicon Series United Chemi-Con Series Series Semiconductor TMOS Power MOSFETs (i.e., MTP30P06V) Transistors Silconix Little Foot MOSFET Series Zetex FZT749 Bipolar Transistor Toshiba 2SA1213 Transistor
Miniature Through-Hole Standard Through-Hole
Sumida Series Coilcraft Series Coiltronics Series
2002 Microchip Technology Inc.
DS21349B-page
TC105
PACKAGING INFORMATION
Package Marking Information
represents first decimal voltage Symbol (300kHz) Voltage
represents product classification; TC105 represents first integer voltage Symbol (300kHz) Voltage
represents production code
DS21349B-page
2002 Microchip Technology Inc.
TC105
Taping Form
Component Taping Orientation 5-Pin SOT-23A (EIAJ SC-74A) Devices
User Direction Feed
Device Marking
Standard Reel Component Orientation Suffix Device (Mark Right Side
Carrier Tape, Number Components Reel Reel Size
Package Carrier Width Pitch Part Full Reel Reel Size
5-Pin SOT-23A
3000
Package Dimensions
SOT-23A-5
.075 (1.90) REF.
.122 (3.10) .098 (2.50) .020 (0.50) .012 (0.30) .122 (3.10) .106 (2.70) .057 (1.45) .035 (0.90) .006 (0.15) .000 (0.00)
.071 (1.80) .059 (1.50)
.037 (0.95) REF.
MAX. .024 (0.60) .004 (0.10)
.010 (0.25) .004 (0.09)
Dimensions: inches (mm)
2002 Microchip Technology Inc.
DS21349B-page
TC105
NOTES:
DS21349B-page
2002 Microchip Technology Inc.
TC105
Sales Support
Data Sheets Products supported preliminary Data Sheet have errata sheet describing minor operational differences recommended workarounds. determine errata sheet exists particular device, please contact following: Your local Microchip sales office Microchip Corporate Literature Center U.S. FAX: (480) 792-7277 Microchip Worldwide Site (www.microchip.com)
Please specify which device, revision silicon Data Sheet (include Literature using. Customer Notification System Register site (www.microchip.com/cn) receive most current information products.
2002 Microchip Technology Inc.
DS21349B-page11
TC105
NOTES:
DS21349B-page12
2002 Microchip Technology Inc.
TC105
Information contained this publication regarding device applications like intended through suggestion only superseded updates. your responsibility ensure that your application meets with your specifications. representation warranty given liability assumed Microchip Technology Incorporated with respect accuracy such information, infringement patents other intellectual property rights arising from such otherwise. Microchip's products critical components life support systems authorized except with express written approval Microchip. licenses conveyed, implicitly otherwise, under intellectual property rights.
Trademarks Microchip name logo, Microchip logo, FilterLab, KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER, PICSTART, MATE, SEEVAL Embedded Control Solutions Company registered trademarks Microchip Technology Incorporated U.S.A. 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 Total Endurance trademarks Microchip Technology Incorporated U.S.A. Serialized Quick Turn Programming (SQTP) service mark Microchip Technology Incorporated U.S.A. other trademarks mentioned herein property their respective companies. 2002, Microchip Technology Incorporated, Printed U.S.A., Rights Reserved.
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Microchip received QS-9000 quality system certification worldwide headquarters, design wafer fabrication facilities Chandler Tempe, Arizona July 1999 Mountain View, California March 2002. Company's quality system processes procedures QS-9000 compliant PICmicro 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, non-volatile memory analog products. addition, Microchip's quality system design manufacture development systems 9001 certified.
2002 Microchip Technology Inc.
DS21349B-page
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PFM/PWM Step-Down DC/DC Controller 57µA (Typ) Supply Current Outp

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