SC553 SEMTECH | Alldatasheet
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Technical content
Features
Revision: April 20, 2004
Description
The SC553 is a low dropout linear regulator that operates from a +2.25V to +6.5V input range and delivers up to 150mA. A PMOS pass transistor allows the low 75µA supply current to remain independent of load, making these devices ideal for battery operated portable equipment such as cellular phones, cordless phones and personal digital assistants. The SC553 has an adjust pin (ADJ) enabling the user to set the output voltage anywhere from 1.25V to 6V. For a low noise version, see SC1453 and for an error flag see SC1457. Other features include low powered shutdown, short circuit protection, thermal shutdown protection and reverse battery protection. The SC553 comes in the tiny 5 lead SOT-23 package. ! Battery Powered Systems ! Cellular Telephones ! Cordless Telephones ! Personal Digital Assistants ! Portable Instrumentation ! Modems ! PCMCIA cards ! 5205 compatible pinout ! 2% output accuracy guaranteed over line, load and temperature ! Guaranteed 150 mA output current ! Very small external components - designed to work with ceramic capacitors ! Output adjustable from 1.25V to 6V ! Very low supply current ! Thermal overload protection ! Reverse battery protection ! Low power shutdown ! Full industrial temperature range ! Surface mount packaging (5 pin SOT-23) U1 SC553 3 4 IN GNDEN ADJ OUT 1uF VIN 1uF VOUT
Applications
Typical Application Circuit +•= 2R 1R1250.1VOUT
2 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 Absolute Maximum Ratings retemaraPl obmySm umixaMs tinU egatloVylppuStupnIV NI 7+ot6.0-V egatloVelbanEV NE Vot6.0- NI V egatloVniPtuptuOV TUO 7+ot6.0-V egatloVniPtsujdAV JDA 7+ot6.0-V tneibmAotnoitcnuJecnatsiseRlamrehT θ AJ 652W /C° esaCotnoitcnuJecnatsiseRlamrehT θ CJ 18W /C° egnaRerutarepmeTtneibmAgnitarepOT A 58+ot04-C ° egnaRerutarepmeTnoitcnuJgnitarepOT J 521+ot04-C ° egnaRerutarepmeTegarotST GTS 051ot56-C ° .ceS01)gniredloS(erutarepmeTdaeLT DAEL 003C ° Unless specified: VIN = 2.25V, VEN = VIN, IOUT = 100µA, CIN = COUT = 1µF, TA = 25°C. Values in bold apply over full operating ambient temperature range. retemaraPl obmySs noitidnoCn iMp yTx aMs tinU NI egnaRegatloVylppuSV NI 52.20 5.6 V tnerruCylppuSI Q I TUO V52.2,Am051otAm0= ≤ VNI ≤ V5.65 70 31A µ 061 tnerruCylppuSetatS-ffOI )FFO(Q VNI V,V5.6= NE V0=1 .00 .1A µ 5.1 JDA egatloVniPtsujdA )1( V JDA I TUO Am1=% 5.1-0 52.1% 5.1+V Am0 ≤ I TUO ≤ V52.2,Am051 ≤ VNI ≤ V5.5 %0.2-% 0.2+ tnerruCtupnIniPtsujdA )2( I JDA V JDA V3.1=5 10.00 05.2A n 000.5 TUO noitalugeReniL )1( GER )ENIL( VNI I,V5.5otV52.2= TUO V,Am1= JDA V= TUO 5.10 1V m noitalugeRdaoL )1( GER )DAOL( I TUO ,Am051otAm1.0=1 -0 1-V m VNI V,V52.2= JDA V= TUO 02-
Electrical Characteristics
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of th e parameters specified in the Electrical Characteristics section is not implied.
3 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 Unless specified: VIN = 2.25V, VEN = VIN, IOUT = 100µA, CIN = COUT = 1µF, TA = 25°C. Values in bold apply over full operating ambient temperature range. retemaraPl obmySs noitidnoCn iMp yTx aMs tinU ).tnoC(TUO timiLtnerruCI MIL 004 Am egatloVtuoporD )3()1( VD I TUO Am1=1 V m I TUO Am05=0 55 6V m I TUO Am001=0 015 21V m 551 I TUO Am051=0 510 91V m 032 NE dlohserhTtupnIelbanEV HI V52.2 ≤ VNI ≤ V5.6 6.1 V VLI V52.2 ≤ VNI ≤ V5.6 4.0 tnerruCsaiBtupnIelbanE )2( I NE V0 ≤ V NE ≤ VNI 5.0- 0 5.0+ Aµ noitcetorPerutarepmeTrevO leveLpirThgiHT IH 051C ° siseretsyHT TSYH 51C ° Notes: (1) Low duty cycle pulse testing with Kelvin connections required. (2) Guaranteed by design. (3) V OUT = 3.3V. Defined as the input to output differential at which the output voltage drops 100mV below the value measured at a differential of 1V. Not measurable on outputs set below 2.25V due to minimum V IN constraints. See Typical Characteristics for typical dropout voltage at other output voltage settings. Electrical Characteristics (Cont.)
4 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 Notes: (1) Only available in tape and reel packaging. A reel contains 3000 devices. (2) Lead free product. This product is fully WEEE and RoHS compliant. rebmuNtraP )1( egakcaP RTKSI355CS5 -32-TOS TRTKSI355CS )2( Top View SOT-23-5L Pin Configuration Ordering Information Block Diagram #niPe maNniPn oitcnuFniP 1N I. niptupnI 2D NG. dedeenfigniknistaehrofdesuebnaC.nipdnuorG 3N E. desugniebtonfiNIottcennoC.nipelbanehgihevitcA 4J DA tiucriCnoitacilppAlacipyTees(redividrotsiserlanretxenaotnipsihtgnitcennoC.niptsujdA Vstes)1egapno TUO :ot 5T UO. Am051otpugnicruos,tuptuorotalugeR Pin Descriptions +•= 2R 1R1250.1VOUT
5 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 yyww Top Mark Bottom Mark yyww = Datecode (Example: 0108) 553 Marking Information Applications Information Theory Of Operation The SC553 is intended for applications where very low dropout voltage, low supply current and low output noise are critical. It provides a very simple, low cost solution that uses very little pcb real estate. Only two external capacitors are required for operation. The SC553 contains a bandgap reference trimmed for optimal temperature coefficient which is fed into the inverting input of an error amplifier. The output voltage of the regulator is divided down externally using a resistor divider and compared to the bandgap voltage via the adjust pin (ADJ). The error amplifier drives the gate of a low R DS(ON) P-channel MOSFET pass device to maintain VOUT such that V ADJ = V REF. An active high enable pin (EN) allows the regulator to be shut down. Pulling this pin low causes the device to enter a very low power shutdown mode, where it will draw typically 0.1µA from the input supply. The regulator has its own current limit circuitry to ensure that the output current will not damage the device during output short, overload or start-up. The current limit is guaranteed to be greater than 400mA to allow fast charging of the output capacitor and high initial currents for DSP initialization. The SC553 includes thermal shutdown circuitry to turn off the device if T J exceeds 150°C (typical), with the device remaining off until T J drops by 15°C (typical). Reverse battery protection circuitry ensures that the device cannot be damaged if the input supply is accidentally reversed, limiting the reverse current to less than 1.5mA. Component Selection - General Output capacitor - Semtech recommends a minimum capacitance of 1µF at the output with an equivalent series resistance (ESR) of < 1 Ω over temperature. While the SC553 has been designed to be used with ceramic capacitors, it does not have to be used with ceramic capacitors, allowing the designer a choice. Increasing the bulk capacitance will further reduce output noise and improve the overall transient response. Input capacitor - Semtech recommends the use of a 1µF ceramic capacitor at the input. This allows for the device being some distance from any bulk capacitance on the rail. Additionally, input droop due to load transients is reduced, improving overall load transient response. External voltage selection resistors - the use of 1% resistors, and designing for a current flow ≥ 10µA is recommended to ensure a well regulated output (thus R2 ≤ 125kΩ ). The output voltage (referring to Figure 1 below) will be: +•= 2R 1R1250.1VOUT U1 SC553 3 4 IN GNDEN ADJ OUT 1uF VIN 1uF VOUT Figure 1
6 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 Dropout Voltage vs. Output Voltage vs. Output Current Typical Characteristics Applications Information (Cont.) Thermal Considerations The worst-case power dissipation for this part is given by: ( ) )MAX(Q)MAX(IN)MAX(OUT)MIN(OUT)MAX(IN)MAX(D IVIVVP •+•−= (1) For all practical purposes, equation (1) can be reduced to the following expression: (2) Looking at a typical application, 3.3V to 2.8V at 150mA: VIN(MAX) = 3.3 + 5% = 3.465V VOUT(MIN) = 2.8V - 2% = 2.744V IOUT = 150mA TA = 85°C Inserting these values into equation (2) gives us: Using this figure, we can calculate the maximum thermal impedance allowable to maintain T J ≤ 125°C: 85125 P TT )MAX(D )MAX(A)MAX(J )MAX(JA °=−=−=θ With the standard SOT-23-5 Land Pattern shown at the end of this datasheet, and minimum trace widths, the thermal impedance junction to ambient for SC553 is 256°C/W. Thus no additional heatsinking is required for this example. The junction temperature can be reduced further (or higher power dissipation can be allowed) by the use of larger trace widths and connecting PCB copper to the GND pin (pin 2), which connects directly to the device substrate. Adding approximately one square inch of PCB copper to pin 2 will reduce θ JA to approximately 130°C/W and T J(MAX) for the example above to approximately 100°C. The use of multi layer boards with internal ground/power planes will lower the junction temperature and improve overall output voltage accuracy. Layout Considerations While layout for linear devices is generally not as critical as for a switching application, careful attention to detail will ensure reliable operation. 1) Attaching the part to a larger copper footprint will enable better heat transfer from the device, especially on PCBs where there are internal ground and power planes. 2) Place the input and output capacitors close to the device for optimal transient response and device behaviour. 3) While the external resistor divider does not need to be close to the device, care should be taken to avoid routing the connections next to any lines carrying large amounts of noise. The simplest solution is to place these resistors close to the device and routing the top of R1 to the load if not adjacent to the part. 4) Connect all ground connections directly to the ground plane. If there is no ground plane, connect to a common local ground point before connecting to board ground. 100 125 150 175 200 225 250 V OUT (V) VD (mV) TA = 25°C Top to bottom: IOUT = 150mA IOUT = 100mA IOUT = 50mA
7 2004 Semtech Corp. www.semtech.com POWER MANAGEMENT SC553 Semtech Corporation Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804 Outline Drawing - SOT-23-5 Land Pattern - SOT-23-5 Contact Information This land pattern is for reference only. Consult your manufacturing group to ensure you meet your companys manufacturability guidelines.