REG101 REG 101 SBVS026C – JULY 2001 DMOS 100mA Low-Dropout Regulator FEATURES DESCRIPTION ● NEW DMOS TOPOLOGY: Ultra Low Dropout Voltage: 60mV typ at 100mA Output capacitor NOT required for stability ● FAST TRANSIENT RESPONSE ● VERY LOW NOISE: 23µVrms ● HIGH ACCURACY: ±1.5% max ● HIGH EFFICIENCY: IGND = 500µA at IOUT = 100mA Not Enabled: IGND = 10nA ● 2.5V, 2.8V, 2.85V, 3.0V, 3.3V, 5.0V, AND ADJUSTABLE OUTPUT VERSIONS ● OTHER OUTPUT VOLTAGES AVAILABLE UPON REQUEST ● FOLDBACK CURRENT LIMIT ● THERMAL PROTECTION ● SMALL SURFACE-MOUNT PACKAGES: SOT23-5 and SO-8 The REG101 is a family of low-noise, low-dropout linear regulators with low ground pin current. Its new DMOS topology provides significant improvement over previous designs, including low dropout voltage (only 60mV typ at full load), and better transient performance. In addition, no output capacitor is required for stability, unlike conventional low-dropout regulators that are difficult to compensate and require expensive low ESR capacitors greater than 1µF. Typical ground pin current is only 500µA (at IOUT = 100mA) and drops to 10nA when not in enabled mode. Unlike regulators with PNP pass devices, quiescent current remains relatively constant over load variation and under dropout conditions. The REG101 has very low output noise (typically 23µVrms for VOUT = 3.3V with CNR = 0.01µF), making it ideal for use in portable communications equipment. Accuracy is maintained over temperature, line, and load variations. Key parameters are tested over the specified temperature range (–40°C to +85°C). The REG101 is well protected—internal circuitry provides a current limit that protects the load from damage. Thermal protection circuitry keeps the chip from being damaged by excessive temperature. The REG101 is available in the SOT23-5 and the SO-8 packages. APPLICATIONS ● ● ● ● ● ● PORTABLE COMMUNICATION DEVICES BATTERY-POWERED EQUIPMENT PERSONAL DIGITAL ASSISTANTS MODEMS BAR-CODE SCANNERS BACKUP POWER SUPPLIES Enable Enable VOUT VIN + 0.1µF NR REG101 (Fixed Voltage Versions) + COUT(1) VIN VOUT + REG101-A + COUT(1) Adj Gnd NR = Noise Reduction 0.1µF R1 Gnd R2 NOTE: (1) Optional. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright © 2000, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. www.ti.com ABSOLUTE MAXIMUM RATINGS(1) Supply Input Voltage, VIN ...................................................... –0.3V to 12V Enable Input ............................................................................ –0.3V to VIN Output Short-Circuit Duration ...................................................... Indefinite Operating Temperature Range (TJ) ................................ –55°C to +125°C Storage Temperature Range (TA) ................................... –65°C to +150°C Lead Temperature (soldering, 3s, SOT23-5, and SO-8) ..................... +240°C NOTE: (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION PACKAGE PACKAGE DRAWING NUMBER PACKAGE MARKING ORDERING NUMBER(1) TRANSPORT MEDIA 5V Output REG101NA-5 SOT23-5 331 R01B " " " " REG101UA-5 SO-8 182 REG101U50 " " " " REG101NA-5/250 REG101NA-5/3K REG101UA-5 REG101UA-5/2K5 Tape and Reel Tape and Reel Rails Tape and Reel SOT23-5 331 R01C " " " REG101NA-3.3/250 REG101NA-3.3/3K REG101UA-3.3 REG101UA-3.3/2K5 Tape and Reel Tape and Reel Rails Tape and Reel REG101NA-3/250 REG101NA-3/3K REG101UA-3 REG101UA-3/2K5 Tape and Reel Tape and Reel Rails Tape and Reel REG101NA-2.85/250 REG101NA-2.85/3K REG101UA-2.85 REG101UA-2.85/2K5 Tape and Reel Tape and Reel Rails Tape and Reel REG101NA-2.8/250 REG101NA-2.8/3K REG101UA-2.8 REG101UA-2.8/2K5 Tape and Reel Tape and Reel Rails Tape and Reel REG101NA-2.5/250 REG101NA-2.5/3K REG101UA-2.5 REG101UA-2.5/2K5 Tape and Reel Tape and Reel Rails Tape and Reel REG101NA-A/250 REG101NA-A/3K REG101UA-A REG101UA-A/2K5 Tape and Reel Tape and Reel Rails Tape and Reel PRODUCT 3.3V Output REG101NA-3.3 " REG101UA-3.3 SO-8 182 REG101U33 " " " " 3V Output REG101NA-3 SOT23-5 331 R01D " " " " REG101UA-3 SO-8 182 REG101U30 " " " " SOT23-5 331 R01N " " " SO-8 182 REG101285 " " " SOT23-5 331 R01E " " " SO-8 182 REG101U28 " " " SOT23-5 331 R01G " " " SO-8 182 REG101U25 " " " 2.85V Output REG101NA-2.85 " REG101UA-2.85 " 2.8V Output REG101NA-2.8 " REG101UA-2.8 " 2.5V Output REG101NA-2.5 " REG101UA-2.5 " Adjustable Output REG101NA-A SOT23-5 331 R01A " " " " REG101UA-A SO-8 182 REG101UA " " " " NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “REG101UA-5/2K5” will get a single 2500-piece Tape and Reel. Many custom output voltage versions, from 2.5V to 5.1V in 50mV increments, are available upon request. Minimum order quantities apply. Contact factory for details. 2 REG101 SBVS026C ELECTRICAL CHARACTERISTICS Boldface limits apply over the specified temperature range, TJ = –40°C to +85°C. At TJ = +25°C, VIN = VOUT + 1V (VOUT = 2.5V for REG101-A), VENABLE = 1.8V, IOUT = 2mA, CNR = 0.01µF, and COUT = 0.1µF(1), unless otherwise noted. REG101NA REG101UA PARAMETER OUTPUT VOLTAGE Output Voltage REG101-2.5 REG101-2.8 REG101-2.85 REG101-3.0 REG101-3.3 REG101-5 REG101-A Reference Voltage Adjust Pin Current Accuracy Over Temperature vs Temperature Includes Line and Load Over Temperature DC DROPOUT VOLTAGE(2) For all models Over Temperature VOLTAGE NOISE Without CNR With CNR (all fixed voltage models) OUTPUT CURRENT Current Limit(3) Over Temperature Short-Circuit Current CONDITION 2.5 VREF IADJ TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance SOT23-5 Surface Mount SO-8 Surface Mount UNITS 50 ±0.8 IOUT = 2mA to 100mA, VIN = (VOUT + 0.4V) to 10V VIN = (VOUT + 0.6V) to 10V VDROP Vn IOUT = 2mA IOUT = 100mA IOUT = 100mA 4 60 f = 10Hz to 100kHz CNR = 0, COUT = 0 CNR = 0.01µF, COUT = 10µF ICL ISC IOUT = 100mA IENABLE 10 100 130 mV mV mV 1 ±1.5 ±2.2 ±2.0 µVrms µVrms 23µVrms/V • VOUT 7µVrms/V • VOUT 130 110 VENABLE ±2.7 V V V V V V V V µA % % ppm/°C % % 5.5 1.267 0.2 ±0.5 dVOUT/dT 170 60 mA mA mA 65 dB 1.8 –0.2 VENABLE = 1.8V to VIN, VIN = 1.8V to 6.5(4) VENABLE = 0V to 0.5V COUT = 1.0µF, RLOAD = 33Ω COUT = 1.0µF, RLOAD = 33Ω 1 2 200 1.5 220 240 VIN 0.5 100 100 IGND V V nA nA µs ms °C °C 160 140 Enable Pin Low INPUT VOLTAGE Operating Input Voltage Range(5) Specified Input Voltage Range Over Temperature MAX 2.5 2.8 2.85 3.0 3.3 5 THERMAL SHUTDOWN Junction Temperature Shutdown Reset from Shutdown GROUND PIN CURRENT Ground Pin Current TYP VOUT RIPPLE REJECTION f = 120Hz ENABLE CONTROL VENABLE High (output enabled) VENABLE Low (output disabled) IENABLE High (output enabled) IENABLE Low (output disabled) Output Disable Time Output Enable Time MIN 500 650 0.2 µA µA µA 1.8 VOUT + 0.4 VOUT + 0.6 10 10 10 V V V –40 –55 –65 +85 +125 +150 °C °C °C IOUT = 2mA IOUT = 100mA VENABLE ≤ 0.5V 400 500 0.01 VIN VIN > 1.8V VIN > 1.8V TJ TJ TA θJA θJA Junction-to-Ambient Junction-to-Ambient 200 150 °C/W °C/W NOTES: (1) The REG101 does not require a minimum output capacitor for stability. However, transient response can be improved with proper capacitor selection. (2) Dropout voltage is defined as the input voltage minus the output voltage that produces a 2% change in the output voltage from the value at VIN = VOUT + 1V at fixed load. (3) Current limit is the output current that produces a 10% change in output voltage from VIN = VOUT + 1V and IOUT = 2mA. (4) For VENABLE > 6.5V, see typical characteristic “IENABLE vs VENABLE”. (5) The REG101 no longer regulates when VIN < VOUT + VDROP (MAX). In drop-out, the impedance from VIN to VOUT is typically less than 1Ω at TJ = +25°C. REG101 SBVS026C 3 PIN CONFIGURATIONS Top View SOT23-5 SO-8 VOUT(2) 1 8 VIN(3) VIN 1 VOUT(2) 2 7 VIN(3) GND 2 NR/Adjust(1) 3 6 NC Enable 3 GND 4 5 Enable 5 VOUT 4 NR/Adjust(1) (N Package) (U Package) NOTE: (1) For REG101A-A: voltage setting resistor pin. All other models: noise reduction capacitor pin. (2) Both pin 1 and pin 2 must be connected. (3) Both pin 7 and pin 8 must be connected. 4 REG101 SBVS026C TYPICAL CHARACTERISTICS For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted. OUTPUT VOLTAGE CHANGE vs IOUT (VIN = VOUT + 1V, Output Voltage % Change Refered to IOUT = 50mA at +25°C) LOAD REGULATION vs TEMPERATURE (VIN = VOUT + 1V) 0.0% 0.80 Output Voltage Change (%) Output Voltage Change (%) 0.60 0.40 +25°C 0.20 +125°C 0.00 –0.20 –0.40 –55°C –0.1% 10mA < IOUT < 100mA –0.2% –0.3% 2mA < IOUT < 1000mA –0.60 –0.80 0 10 20 30 40 50 60 70 80 90 –0.4% –50 100 –25 0 0.10 15 0.08 IOUT = 2mA 5 IOUT = 50mA 0 –5 –10 IOUT = 100mA –15 1 2 3 75 100 125 IOUT = 100mA 0.06 0.04 0.02 (VOUT + 1V) < VIN < 10V 0.00 –0.02 –0.04 –0.06 –0.08 –20 0 50 LINE REGULATION vs TEMPERATURE 20 Output Voltage Change (%) Output Voltage Change (mV) LINE REGULATION (Referred to VIN = VOUT + 1V at IOUT = 50mA) 10 25 Temperature (°C) IOUT (mA) 4 5 6 7 8 –0.10 –50 (VOUT + 0.4V) < VIN < 10V –25 0 VIN – VOUT (V) 25 50 75 100 125 Temperature (°C) DC DROPOUT VOLTAGE vs TEMPERATURE DC DROPOUT VOLTAGE vs IOUT 100 100 DC Dropout Voltage (mV) DC Dropout Voltage (mV) IOUT = 100mA 80 +125°C 60 +25°C 40 –55°C 20 0 0 10 20 30 40 50 60 IOUT (mA) REG101 SBVS026C 70 80 90 100 80 60 40 20 0 –50 –25 0 25 50 75 100 125 Temperature (°C) 5 TYPICAL CHARACTERISTICS (Cont.) For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted. OUTPUT VOLTAGE ACCURACY HISTOGRAM OUTPUT VOLTAGE DRIFT HISTOGRAM 18 30 16 Percentage of Units (%) Percentage of Units (%) 25 14 12 10 8 6 4 20 15 10 5 2 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1.0 0.8 0.6 0.4 0.2 0.0 –0.2 –0.4 –0.6 –0.8 –1.0 0 Error (%) VOUT Drift (ppm/°C) OUTPUT VOLTAGE vs TEMPERATURE (Output Voltage % Change Referred to IOUT = 50mA at +25°C) GROUND PIN CURRENT, NOT ENABLED vs TEMPERATURE 1µ 0.50 VENABLE = 0.5V VIN = VOUT + 1V 0.30 100n IOUT = 2mA 0.20 0.10 0.00 IGND (A) Output Voltage Change (%) 0.40 IOUT = 50mA –0.10 10n –0.20 1n –0.30 IOUT = 100mA –0.40 –0.50 –50 –25 0 25 50 75 100 100p –50 125 –25 0 25 50 75 100 125 Temperature (°C) Temperature (°C) GROUND PIN CURRENT vs IOUT GROUND PIN CURRENT vs TEMPERATURE 600 600 VOUT = 5V VOUT = 5.0V 500 IOUT = 100mA 575 550 VOUT = 3.3V 300 IGND (µA) IGND (µA) 400 VOUT = 2.5V 200 525 VOUT = 3.3V 500 475 450 VOUT = 2.5V 100 425 VIN = VOUT + 1V 0 0 10 20 30 40 50 IOUT (mA) 6 60 70 80 90 100 VIN = VOUT + 1V 400 –50 –25 0 25 50 75 100 125 Temperature (°C) REG101 SBVS026C TTYPICAL CHARACTERISTICS (Cont.) For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted. RIPPLE REJECTION vs FREQUENCY RIPPLE REJECTION vs (VIN – VOUT) 80 30 IOUT = 2mA REG101-3.3 25 IOUT = 2mA COUT = 10µF 60 50 IOUT = 100mA Ripple Rejection (dB) Ripple Rejection (dB) 70 IOUT = 100mA COUT = 10µF 40 30 20 COUT = 0µF 10 20 15 10 Frequency = 100kHz COUT = 10µF IOUT = 100mA 5 0 0 10 100 1k 10k 100k 1M 10M 0 0.1 0.2 0.3 Frequency (Hz) 0.4 0.5 RMS NOISE VOLTAGE vs COUT REG101-5.0 0.9 1 100 REG101-5.0 Noise Voltage (µVrms) Noise Voltage (µVrms) 0.8 110 50 40 REG101-3.3 30 20 REG101-2.5 10 CNR = 0.01µF 10Hz < BW < 100kHz 0 90 REG101-3.3 80 REG101-2.5 70 60 50 40 CNR = 0µF 10Hz < BW < 100kHz 30 20 1 0.1 10 1 10 COUT (µF) COUT = 1µF COUT = 0µF eN (µV/√Hz) 1 IOUT = 100mA CNR = 0.01µF 1 COUT = 1µF 0.1 COUT = 0µF COUT = 10µF 0.01 COUT = 10µF 0.01 10 100 1k Frequency (Hz) REG101 SBVS026C 10k 1k NOISE SPECTRAL DENSITY 10 IOUT = 100mA CNR = 0µF 0.1 100 CNR (pF) NOISE SPECTRAL DENSITY eN (µV/√Hz) 0.7 RMS NOISE VOLTAGE vs CNR 60 10 0.6 VIN - VOUT (V) 10k 100k 10 100 1k 10k 100k Frequency (Hz) 7 TYPICAL CHARACTERISTICS (Cont.) For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted. CURRENT LIMIT vs TEMPERATURE FOLDBACK CURRENT LIMIT 180 3.5 160 3.0 ICL 140 2.5 2.0 IOUT (mA) ICL 1.5 100 80 1.0 ISC ISC 60 0.5 0 20 40 60 80 100 120 140 160 180 40 –50 –25 0 25 50 LOAD TRANSIENT RESPONSE LINE TRANSIENT RESPONSE REG101-3.3 VIN = 4.3V 200mV/div COUT = 0µF VOUT COUT = 10µF VOUT IOUT 10mA COUT = 0 REG101-3.3 IOUT = 100mA VOUT VOUT 5.3V VIN 4.3V 10µs/div 50µs/div TURN-ON TURN-OFF VOUT 250µs/div COUT = 1.0µF RLOAD = 33Ω VOUT COUT = 0µF RLOAD = 1600Ω VENABLE 1V/div 1V/div COUT = 10µF RLOAD = 33Ω REG101-3.3 VIN = VOUT + 1V CNR = 0.01µF COUT = 10µF RLOAD = 33Ω 1V/div COUT = 0µF RLOAD = 33Ω 125 COUT = 10µF COUT = 0µF RLOAD = 1600Ω 1V/div 100 Output Current (mA) 100mA 8 75 Temperature (°C) 50mV/div 0 200mV/div VIN = VOUT + 1V 120 50mV/div Output Voltage (V) REG101-3.3 VENABLE REG101-3.3 CNR = 0.01µF 200µs/div REG101 SBVS026C TYPICAL CHARACTERISTICS (Cont.) For all models, at TJ = +25°C and VENABLE = 1.8V, unless otherwise noted. IENABLE vs VENABLE POWER UP/POWER DOWN 10µ VOUT = 3.0V RLOAD = 30Ω 500mV/div IENABLE (A) 1µ 100n T = +25°C T = +125°C VIN 10n VOUT T = –55°C 1n 6 7 8 9 10 1s/div VENABLE (V) RMS NOISE VOLTAGE vs CADJ ADJUST PIN CURRENT vs TEMPERATURE 0.350 80 REG101–A 70 0.250 IADJ (µA) COUT = 0.1µF 10Hz < frequency < 100kHz 60 Vn (rms) 0.300 VOUT = 3.3V 50 40 0.200 0.150 0.100 30 0.050 0.000 20 10 200mV/div 100 1k 10k –50 100k 10mA REG101 SBVS026C 25 50 75 100 LOAD TRANSIENT-ADJUSTABLE VERSION LINE TRANSIENT-ADJUSTABLE VERSION COUT = 0 VOUT 50mV/div COUT = 10µF 125 COUT = 0 VOUT COUT = 10µF VOUT VOUT REG101–A 100mA 0 Temperature (°C) 50mV/div 200mV/div –25 CADJ (pF) VIN = 4.3V 5.3V VOUT = 3.3V IOUT REG101–A IOUT = 100mA CFB = 0.01µF VOUT = 3.3V VIN 4.3V 9 BASIC OPERATION the input supply voltage. This is recommended to improve ripple rejection by reducing input voltage ripple. The REG101 series of LDO (Low Drop-Out) linear regulators offers a wide selection of fixed output voltage versions and an adjustable output version. The REG101 belongs to a family of new generation LDO regulators that utilize a DMOS pass transistor to achieve ultra-low dropout performance and freedom from output capacitor constraints. Ground pin current remains under 650µA over all line, load, and temperature conditions. All versions have thermal and overcurrent protection, including foldback current limit. The REG101 does not require an output capacitor for regulator stability and is stable over most output currents and with almost any value and type of output capacitor up to 10µF or more. For applications where the regulator output current drops below several milliamps, stability can be enhanced by: adding a 1kΩ to 2kΩ load resistor; using capacitance values less than 10µF; or keeping the effective series resistance greater than 0.05Ω including the capacitor’s ESR and parasitic resistance in printed circuit board traces, solder joints, and sockets. Figure 1 shows the basic circuit connections for the fixed voltage models. Figure 2 gives the connections for the adjustable output version (REG101A) and example resistor values for some commonly used output voltages. Values for other voltages can be calculated from the equation shown in Figure 2. INTERNAL CURRENT LIMIT The REG101 internal current limit has a typical value of 170mA. A foldback feature limits the short-circuit current to a typical short-circuit value of 60mA. This helps to protect the regulator from damage under all load conditions. A characteristic of VOUT versus IOUT is given in Figure 3 and in the Typical Characteristics section. FOLDBACK CURRENT LIMIT 3.5 Although an input capacitor is not required, it is good analog design practice to connect a 0.1µF low ESR capacitor across REG101 In 0.1µF REG101-3.3 Output Voltage (V) Enable VIN 3.0 Gnd NR 2.0 ICL 1.5 1.0 ICL VOUT Out 2.5 0.5 COUT 0 CNR 0.01µF 0 20 40 60 80 100 120 140 160 180 Output Current (mA) Optional FIGURE 1. Fixed Voltage Nominal Circuit for REG101. FIGURE 3. Foldback Current Limit of the REG101-3.3 at 25°C. Enable 3 EXAMPLE RESISTOR VALUES 5 VOUT 1 VIN REG101 4 0.1µF IADJ 2 Gnd R1 CFB 0.01µF COUT VOUT (V) R1 (W)(1) R2 (Ω)(1) 2.5 11.3k 1.13k 11.5k 1.15k 3.0 15.8k 1.58k 11.5k 1.15k 3.3 18.7k 1.87k 11.5k 1.15k 5.0 34.0k 3.40k 11.5k 1.15k Load Adj R2 Optional Pin numbers for SOT23 package. NOTE: (1) Resistors are standard 1% values. VOUT = (1 + R1/R2) • 1.267V To reduce current through divider, increase resistor values (see table at right). As the impedance of the resistor divider increases, IADJ (~200nA) may introduce an error. CFB improves noise and transient response. FIGURE 2. Adjustable Voltage Circuit for REG101A. 10 REG101 SBVS026C OUTPUT NOISE A precision band-gap reference is used for the internal reference voltage, VREF. This reference is the dominant noise source within the REG101 and it generates approximately 29µVrms in the 10Hz to 100kHz bandwidth at the reference output. The regulator control loop gains up the reference noise, so that the noise voltage of the regulator is approximately given by: RMS NOISE VOLTAGE vs CNR 110 100 REG101-5.0 Noise Voltage (µVrms) ENABLE The Enable pin is active HIGH and compatible with standard TTL-CMOS levels. Inputs below 0.5V (max) turn the regulator off and all circuitry is disabled. Under this condition, ground pin current drops to approximately 10nA. When a pull-up resistor is used, and operation down to VIN = 1.8V is required, use values < 50kΩ. 90 REG101-3.3 80 REG101-2.5 70 60 50 40 CNR = 0µF 10Hz < BW < 100kHz 30 20 1 100 10 10k 1k CNR (pF) FIGURE 5. Output Noise versus Noise Reduction Capacitor. R + R2 V VN = 29 µVrms 1 = 29 µVrms • OUT R2 VREF Since the value of VREF is 1.267V, this relationship reduces to: VN = 23 µVrms • VOUT V Connecting a capacitor, CNR, from the Noise Reduction (NR) pin to ground, as shown in Figure 4, forms a low-pass filter for the voltage reference. For CNR = 10nF, the total noise in the 10Hz to 100kHz bandwidth is reduced by approximately a factor of 2.8 for VO = 3.3V. This noise reduction effect is shown in Figure 5 and as “RMS Noise Voltage vs CNR” in the Typical Characteristics section. Noise can be further reduced by carefully choosing an output capacitor, COUT. Best overall noise performance is achieved with very low (< 0.22µF) or very high (> 2.2µF) values of COUT. See “RMS Noise Voltage vs COUT” in the Typical Characteristics section. The REG101 utilizes an internal charge pump to develop an internal supply voltage sufficient to drive the gate of the DMOS pass element above VIN. The charge-pump switching noise (nominal switching frequency = 2MHz) is not measurable at the output of the regulator over most values of COUT and IOUT. The REG101 adjustable version does not have the noisereduction pin available, however, the adjust pin is the summing junction of the error amplifier. A capacitor, CFB, connected from the output to the adjust pin will reduce both the output noise and the peak error from a load transient. See the typical characteristics for output noise performance. VIN NR (fixed output versions only) Low Noise Charge Pump CNR (optional) Enable VREF (1.26V) DMOS Pass Transistor VOUT Over Current Over Temp Protection R1 R2 Adj (Adjustable Versions) REG101 NOTE: R1 and R2 are internal on fixed output versions. FIGURE 4. Block Diagram. REG101 SBVS026C 11 DROP-OUT VOLTAGE The REG101 uses an N-channel DMOS as the “pass” element. When the input voltage is within a few tens of millivolts of the output voltage, the DMOS device behaves like a resistor. Therefore, for low values of VIN to VOUT, the regulator’s input-to-output resistance is the RdsON of the DMOS pass element (typically 600mΩ). For static (DC) loads, the REG101 will typically maintain regulation down to VIN to VOUT voltage drop of 60mV at full rated output current. In Figure 6, the bottom line (DC dropout) shows the minimum VIN to VOUT voltage drop required to prevent drop-out under DC load conditions. For large step changes in load current, the REG101 requires a larger voltage drop across it to avoid degraded transient response. The boundary of this “transient drop-out” region is shown as the top line in Figure 6. Values of VIN to VOUT voltage drop above this line insure normal transient response. In the transient dropout region between “DC” and “Transient”, transient response recovery time increases. The time required to recover from a load transient is a function of both the magnitude and rate of the step change in load current and the available “headroom” VIN to VOUT voltage drop. Under worst-case conditions (full-scale load change with VIN to VOUT voltage drop close to DC dropout levels), the REG101 can take several hundred microseconds to re-enter the specified window of regulation. 140 Dropout Voltage (mV) 120 Full Scale IOUT Transient 100 80 60 TRANSIENT RESPONSE The REG101 response to transient line and load conditions improves at lower output voltages. The addition of a capacitor (nominal value 0.47µF) from the output pin to ground may improve the transient response. In the adjustable version, the addition of a capacitor, CFB (nominal value 10nF), from the output to the adjust pin will also improve the transient response. THERMAL PROTECTION The REG101 has thermal shutdown circuitry that protects the regulator from damage. The thermal protection circuitry disables the output when the junction temperature reaches approximately 160°C, allowing the device to cool. When the junction temperature cools to approximately 140°C, the output circuitry is again enabled. Depending on various conditions, the thermal protection circuit may cycle on and off. This limits the dissipation of the regulator, but may have an undesirable effect on the load. Any tendency to activate the thermal protection circuit indicates excessive power dissipation or an inadequate heat sink. For reliable operation, junction temperature should be limited to 125°C, maximum. To estimate the margin of safety in a complete design (including heat sink), increase the ambient temperature until the thermal protection is triggered. Use worst-case loads and signal conditions. For good reliability, thermal protection should trigger more than 35°C above the maximum expected ambient condition of your application. This produces a worst-case junction temperature of 125°C at the highest expected ambient temperature and worst-case load. The internal protection circuitry of the REG101 has been designed to protect against overload conditions. It was not intended to replace proper heat sinking. Continuously running the REG101 into thermal shutdown will degrade reliability. 40 DC 20 0 0 25 50 75 100 125 150 IOUT (mA) FIGURE 6. Transient and DC Dropout. 12 REG101 SBVS026C POWER DISSIPATION The REG101 is available in two different package configurations. The ability to remove heat from the die is different for each package type and, therefore, presents different considerations in the printed circuit-board layout. The PCB area around the device that is free of other components moves the heat from the device to the ambient air. While it is difficult-to-impossible to quantify all of the variables in a thermal design of this type, performance data for several configurations are shown in Figure 7. Power dissipation depends on input voltage, load condition, and duty cycle. Power dissipation is equal to the product of the average output current times the voltage across the output element, VIN to VOUT voltage drop. Power dissipation can be minimized by using the lowest possible input voltage necessary to assure the required output voltage. REGULATOR MOUNTING Solder pad footprint recommendations for the various REG101 devices are presented in the Application Bulletin AB-132, “Solder Pad Recommendations for Surface-Mount Devices” (SBFA015), available from the Texas Instruments web site (www.ti.com). PD = (VIN – VOUT ) • I OUT(AVG) 1.2 Power Dissipation (Watts) CONDITIONS SOT23-5 SO-8 1.0 0.8 0.6 PACKAGE θJA SOT23-5 200°C/W SO-8 150°C/W 0.4 0.3 0 0 25 50 75 100 125 Ambient Temperature (°C) FIGURE 7. Maximum Power Dissipation versus Ambient Temperature for the Various Packages. REG101 SBVS026C 13 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. 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