- PDF Free Download

Size: px

Start display at page:

Download ""

Milo Bates
5 years ago
Views:

1 8mA LOW DROP POSITIVE REGULATORS USTABLE AND FIXED 2.85V, 3.3V, 5.V FEATURES Space-saving SOT-223 Package Pin Compatible with Older Adjustable 3 Terminal Regulators Adjustable or Fixed Voltages of 2.85V, 3.3V or 5.V High Output Current... 8mA Low Dropout Voltage V at I = 8mA Guaranteed Dropout Voltage at Multiple Current Levels Line Regulation (Max)....2% Load Regulation (Max)....4% APPLICATIONS Active SCSI Terminators High Efficiency Linear Regulators Post Regulators for Switching Supplies Battery Chargers 5V - 3.3V Linear Regulators ORDERG FORMATION Part Number* Package Part Marking -CDB SOT CDB SOT CDB SOT CDB SOT CEB DDPAK CEB DDPAK-3-3.3CEB DDPAK-3-5.CEB DDPAK-3 *Ambient temperature range is determined by maximum operating power dissipation and a maximum die temperature of 125 C (see Power Dissipation and Thermal Design Section). TYPICAL APPLICATION GENERAL DESCRIPTION The is a low-dropout positive voltage regulator (LDO) with 8mA output current capability. It is available in fixed and adjustable output voltage versions, 2.85V (active SCSI terminators), 3.3V and 5.V. Output/reference voltage accuracy is guaranteed to ±1.%. Over-current protection is integrated onto the chip. Dropout is specified at 1.2V maximum at full rated output current and less than 1.V at low loads (<1mA). The SOT-223 package makes the especially attractive for tight physical layouts. For stability, a output capacitor is required. The is an NPN-based design which has significantly lower unused quiescent current than similar PNP-based regulators. P CONFIGURATIONS TAB IS V SOT Lead Package FRONT VIEW / DDPAK-3 FRONT VIEW / 11Ω V to 5.25V 22µF 11Ω 11Ω 18 to 27 LES Active Terminator for SCSI-2 Bus -5 6/5/97 TelCom Semiconductor reserves the right to make changes in the circuitry and 1 specifications of its devices.

2 ABSOLUTE MAXIMUM RATGS* Input Voltage Operating Voltage:, -3.3, V V Surge Voltage:, -3.3, V Operating Junction Temperature... C to 125 C Storage Temperature C to 15 C Lead Temperature (Soldering 1 sec)... 3 C *Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS Symbol Parameter Test Conditions Min Typ Max Unit Reference I = 1mA, (V V ) = 2V, T J = 25 C V Voltage 1 I 8mA, 1.4V (V V ) 1V (Note 1) Output Voltage I = 1mA, V = 4.85V, T J = 25 C V I 8mA, 4.25V V 1V (Note 1) I 5mA, V = 3.95V (Note 1) I = 1mA, V = 5.3V, T J = 25 C V I 8mA, 4.75V V 1V (Note 1) I = 1mA, V = 7V, T J = 25 C V I 8mA, 6.5V V 12V (Note 1) Line Regulation I = 1mA, 1.5V V V 15V (Notes 1 & 2).35.2 % I = ma, 4.25V V 1V (Notes 1 & 2) 1 6 mv -3.3 I = ma, 4.75V V 15V (Notes 1 & 2) I = ma, 6.5V V 15V (Notes 1 & 2) 1 1 Load Regulation (V V ) = 3V, 1mA, I 8mA (Notes 1 & 2).1.4 % V = 4.25V, I 8mA (Notes 1 & 2) 1 1 mv -3.3 V = 4.75V, I 8mA (Notes 1 & 2) V = 6.5V, I 8mA (Notes 1 & 2) 1 15 Dropout Voltage I = 1mA, (Note 1 & 3) V I = 5mA, (Note 1 & 3) I = 8mA, (Note 1 & 3) Current Limit (V V ) = 5V, T J = 25 C ma Minimum Load (V V ) = 15V (Note 1 & 4) ma Current Quiescent V 1V (Note 1) 5 1 ma Current -3.3 V 15V (Note 1) V 15V (Note 1) 5 1 Thermal Regulation T A = 25 C, 3msec Pulse.1.1 %W Ripple Rejection f RIPPLE = 12Hz (V V ) = 3V, V RIPPLE = 1Vp-p ( Note 1) 6 75 db Adjust Pin Current (Note 1) µa Adjust Pin Current Change 1mA I 8mA, 1.4V (V V ) 1V (Note 1).2 5 µa Temperature Stability.5 % Long Term Stability T A = 125 C, 1 Hrs..3 % RMS Output Noise (% of V ), 1Hz f 1kHz.3 % Thermal Resistance (Junction to Case, at Tab) 15 C/W NOTES: 1. Specifications apply over the full operating temperature range. 2. See thermal regulation specification for changes in output voltage due to heating effects. Load regulation and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. 3. Dropout voltage is specified over the full output current range of the device. Dropout voltage is defined as the minimum input/output differential measured at the specified output current. Test points and limits are also shown on the Dropout Voltage curve. 4. Minimum load current is defined as the minimum output current required to maintain regulation. -5 6/5/97 2

3 APPLICATIONS Overload Protection The is protected against current (short-circuit) and thermal overload conditions. Thermal protection is triggered by a chip temperature exceeding 165 C. Current overload is triggered at approximately 95mA. Stability and Load Regulation The requires a capacitor from V to to provide compensation feedback to the internal gain stage. This is to ensure stability at the output terminal. Typically, a tantalum or 5µF aluminum electrolytic is sufficient. NOTE: It is important that the ESR for this capacitor does not exceed.5ω. The output capacitor does not have a theoretical upper limit and increasing its value will increase stability. C = or more is typical for high current regulator designs. NOTE: See Protection Diodes for limitations. Another benefit of larger output capacitance is improved transient load response (large di/dt in the load). Protection Diodes Typically no protection diodes are necessary for the. Unlike older regulators, the pin is protected internally from excessive currents. The pin can be driven with voltage transients as high as ±25V with respect to the output without damage to the device. Likewise, a diode between the input and output is not typically required. If the input voltage collapses the internal circuitry can absorb ~2A transient currents (<1µsec) without damage. This reverse current is much larger than most power supply designs can generate. However, if the output capacitor is VERY large (>1µF), instantaneous currents can be high enough to damage the chip. In this case, a high-current, fast-response diode is recommended. (See Figure 1). Output Voltage Adjust Like most LDOs, the regulates the output by comparing the output voltage, or a multiple thereof, to an internally generated reference voltage. On the adjustable version, the V REF is available externally as 1.25V (±1%) between V and (See Figure 2). The voltage divider formed by and should be set to conduct 1mA (minimum output load). The output voltage is given by the following equation: V = V REF ( 1 ) I On fixed voltage versions of the, the voltage divider is provided internally. Load Regulation The load regulation is limited by the resistance of the wire connecting it to the load (R p, Figure 3). For the adjustable version, the best load regulation is accomplished when the top of the resistor divider () is connected directly to the output pin of the, NOT to the high side of the load (Figure 3). When so connected, R p is not multiplied by the divider ratio. For the fixed output versions, the top of is internally connected to the output and the ground pin can be connected to the low side of the load as a negative side sense if, so desired. D1 1N42 (OPTIONAL) V C C 15µF V V I 5µA V REF V = V REF ( 1 ) I V Figure 1. Figure 2. Basic Adjustable Regulator -5 6/5/97 3

4 V Rp PARASITIC LE RESISTANCE Table 1. Thermal Copper Area Resistance Topside* Backside Board Area (Junction-to-Ambient) 25 Sq. mm 25 Sq. mm 25 Sq. mm 45 C/W 1 Sq. mm 25 Sq. mm 25 Sq. mm 45 C/W CONNECT TO CASE R L 225 Sq. mm 25 Sq. mm 25 Sq. mm 53 C/W 1 Sq. mm 25 Sq. mm 25 Sq. mm 59 C/W 1 Sq. mm 1 Sq. mm 1 Sq. mm 52 C/W 1 Sq. mm 1 Sq. mm 55 C/W *Tab of device attached to topside copper Figure 3. Connections for Best Load Regulation Power Dissipation and Thermal Design As mentioned earlier, the has thermal overload protection which limits internal temperature to 165 C. However, device functionality is only guaranteed to a maximum junction temperature of 125 C. Since internal power dissipation can be >1 watt, careful thermal design is essential. The is supplied in a SOT-223 package which is intended to be directly surface-mounted to the PC-board. Because there is no dedicated heat sink, power dissipation to ambient is performed largely by the PC board and its copper material. The power dissipation and junction temperature for the in a SOT-223 are given by the following equations: P D = (V V ) x (I ) T JUNCTION = T AMBIENT (P D x Θ JA ) CONNECT TO LOAD NOTE: T JUNCTION must not exceed 125 C The Θ JC (junction to external tab) for the SOT-223 is 15 C/W. Depending upon heatsink parameters, the Θ CA can be as low as 3 C/W. Therefore, the total thermal resistance (Θ JA ) is at least 45 C/W. Table 1 shows thermal resistance measurements taken with the mounted on 1/16 inch 2-layer PCB with 1oz. copper foil. NOTE: The TAB pin does not have to be soldered to all copper layers for effective heat transfer. Use Table 1 only as a rough guide since thermal interactions with adjacent components cannot be predicted. Soldering Methods The recommended methods of soldering the SOT-223 package are: vapor phase re-flow and infrared re-flow with component preheat within 65 C of the solder temperature. Hand soldering and wave soldering methods are not recommended since they can damage the part with excessive thermal gradients across the surface area of the package. Thermal shock to the package (>3 C per second) must be minimized. Ripple Rejection Ripple Rejection curves were generated using an adjustable output with a bypass capacitor from to ground. To obtain the performance shown in the curves, the impedance of the bypass capacitor (at the ripple frequency) should be less than. is typically 1Ω to 2Ω. For example at 12Hz, with = 1Ω, the adjust capacitor should be at least 13µF. Only.16µF would be required at 1kHz. The output ripple increases as the ratio of the output voltage to the reference voltage (V /V REF ) in fixed voltage devices, and adjustable devices without an adjust pin capacitor. For example, at 5V, output ripple will increase by a factor of 4 (5/1.25V). Ripple rejection will be reduced by 12db from the value shown on the curve. -5 6/5/97 4

5 TYPICAL APPLICATIONS 1.2V-1V Adjustable Regulator 5V Regulator with Shutdown V C1* 1k 121Ω C2 V** V SHDN 1k 2N394 1k 121Ω 1% 365Ω 1% 5V * NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS ** V = 1.25V ( 1 ) Remote Sensing V 25Ω 121Ω R p (MAX DROP 3mV) V LM31A kΩ RL PUT 5V 365Ω 1pF 5µF RETURN 25Ω RETURN Adjusting Output Voltage of Fixed Regulators Battery Charger V > 12V -5. 5V TO 1V V 1.25V IF RS V * 1k *OPTIONAL IMPROVES RIPPLE REJECTION V 1.25V (1 ) IF = RS (1 ) IF V = 1 RS (1 ) -5 6/5/97 5

6 TYPICAL APPLICATIONS (Cont.) Battery Backed Up Regulated Supply Improving Ripple Rejection V 6.5V SELECT FOR CHARGE RATE -5. 5Ω V LE 5.V BATTERY V V 16.5V 121Ω 1% 15µF *C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE AT RIPPLE FREQUENCY 365Ω 1% C1* High Efficiency Dual Supply FEEDBACK PATH MUR41 47µF 3.3V PUT (TYPICAL) V MUR41 47µF -5. 5V.5A 1N42 SWITCHG REGULATOR MUR41 47µF -5. 1N42 5V.5A Low Dropout Negative Supply V -5. FLOATG PUT V = 5V -5 6/5/97 6

7 TYPICAL CHARACTERISTICS DROP VOLTAGE (V) Dropout Voltage (V - V ) PUT CURRENT (ma) TJ = 25 C TJ = 125 C DICATES GUARRANTEED TEST POT MIMUM OPERATG CURRENT (ma) Minimum Operating Current (Adjustable Device) T J = 125 C TJ = 25 C TJ = 55 C PUT/PUT DIFFERENTIAL (V) SHORT CIRCUIT CURRENT (A) Short-Circuit Current TJ = 125 C T J = 25 C PUT/PUT DIFFERENTIAL (V) PUT VOLTAGE DEVIATION (%) Load Regulation I LOAD = 8mA TEMPERATURE ( C) RIPPLE REJECTION (db) Ripple Rejection V RIPPLE 3Vp-p (V V ) 3V 2 C = 2µF AT f < 6Hz 1 C = 25µF AT f > 6Hz I =.5A 1 1 1k 1k 1k FREQUENCY (Hz) V RIPPLE.5Vp-p RIPPLE REJECTION (db) Ripple Rejection vs. Current V = 5V C = 25µF C = 25µF f RIPPLE = 12kHz V RIPPLE 3Vp-p f RIPPLE = 2kHz V RIPPLE.5Vp-p PUT CURENT (A) -5 6/5/97 7

8 TYPICAL CHARACTERISTICS (Cont.) Temperature Stability Adjust Pin Current 2. 1 PUT VOLTAGE CHANGE (%) UST P CURRENT (Aµ) TEMPERATURE ( C) TEMPERATURE ( C) Load Transient Response -5 Load Transient Response PUT VOLTAGE DEVIATION (V) LOAD CURRENT (A) C = C = TANTALUM V = 4.25V PRELOAD =.1A PUT VOLTAGE DEVIATION (V) LOAD CURRENT (A) C = C = TANTALUM V = 6.5V PRELOAD =.1A TIME (µsec) TIME (µsec) Line Transient Response -5 Line Transient Response PUT VOLTAGE DEVIATION (mv) C = 1µF C = TANTALUM I =.1A PUT VOLTAGE DEVIATION (mv) C = 1µF C = TANTALUM I =.1A PUT VOLTAGE (V) TIME (µsec) PUT VOLTAGE (V) TIME (µsec) -5 6/5/97 8

9 PACKAGE DIMENSIONS SOT (6.7).248 (6.3).122 (3.1).114 (2.9).287 (7.3).264 (6.7).146 (3.7).13 (3.3).41 (1.4).33 (.84).9 (2.3) TYP..31(.8).24 (.6).71 (1.8) MAX..4 (.1).8 (.2) 1 MAX..181 (4.6) TYP..36 (.91) M..14 (.35).9 (.24) DDPAK-3.67 (1.7).45 (1.14).41 (1.41).385 (9.78).183 (4.65).17 (4.32).55 (1.4).45 (1.14).65 (15.37).549 (13.95).37 (9.4).329 (8.38).51 (1.3).49 (1.24).37 (.94).26 (.66) 3-7 (5x).26 (.66).14 (.36).1 (.25). (.).11 (2.79).68 (1.72).1 (2.54) TYP. - 8 Dimensions: inches (mm) Sales Offices TelCom Semiconductor 13 Terra Bella Avenue P.O. Box 7267 Mountain View, CA TEL: FAX: liter@c2smtp.telcom-semi.com -5 6/5/97 TelCom Semiconductor Austin Product Center 911 Burnet Rd. Suite 214 Austin, TX TEL: FAX: TelCom Semiconductor H.K. Ltd. 1 Sam Chuk Street, Ground Floor San Po Kong, Kowloon Hong Kong TEL: FAX:

Advanced Monolithic Systems

Advanced Monolithic Systems 8mA LOW DROPOUT OLTAGE REGULATOR FEATURES Three Terminal Adjustable or Fixed oltages* 1.5, 1.8, 2.5, 2.85, 3.3 and 5. Output Current of 8mA Operates Down to 1 Dropout Line Regulation:.2