DEMO MANUAL DC330 LOW DROPOUT REGULATOR LT1761 100mA Low Noise Micropower LDO Regulators U DESCRIPTIO Demonstration circuit DC330 comprises two low noise micropower voltage regulators using the LT®1761 in the 5-lead SOT-23 package. These circuits are primarily used in cellular phones, voltage controlled oscillators, RF power supplies and as local regulators in larger systems. Their ability to tolerate a wide variety of output capacitors makes them ideal in space- and cost-sensitive systems. , LTC and LT are registered trademarks of Linear Technology Corporation. WW U W PERFORmANCE SU ARY TA = 25°C, VIN = 2.3V, VSHDN = 5V, ILOAD = 1mA, VOUT = 1.22V (JP1 or JP3 set on pins 1 and 2), unless otherwise specified. PARAMETER CONDITIONS MIN Input Voltage Range TYP 2.3 Output Voltage (Note 1) 1.205 1.220 MAX UNITS 20 V 1.235 V Output Voltage (Note 1) VIN = 2.8V, JP1 or JP3 on Pins 5 and 6 1.764 1.802 1.839 V Output Voltage (Note 1) VIN = 3V, JP1 or JP3 on Pins 7 and 8 1.954 1.999 2.044 V Output Voltage (Note 1) VIN = 3.5V, JP1 or JP3 on Pins 9 and 10 2.455 2.506 2.571 V Output Voltage (Note 1) VIN = 3.8V, JP1 or JP3 on Pins 11 and 12 2.742 2.817 2.894 V Output Voltage (Note 1) VIN = 4V, JP1 or JP3 on Pins 13 and 14 2.936 3.019 3.103 V Output Voltage (Note 1) VIN = 4.3V, JP1 or JP3 on Pins 15 and 16 3.207 3.300 3.396 V Output Voltage (Note 1) VIN = 5V, JP1 or JP3 on Pins 17 and 18 4.848 5.006 5.167 Line Regulation ∆VIN = 2.3V to 20V 1 5 mV Quiescent Current ILOAD = 0mA 20 35 µA 0.2 1 % 0.65 0.8 1.8 V V Load Regulation ∆ILOAD = 1mA to 100mA SHDN Pin Threshold (LT1761-SD) On-to-Off Off-to-On, ILOAD = 100mA Output Voltage Noise (LT1761-BYP) 0.45 ILOAD = 100mA, BW = 10Hz to 100kHz 20 V µVRMS Note 1: Output voltage variations include ±1% tolerance of feedback divider network. For tighter voltage range, use lower tolerance resistors or use fixed voltage output devices. U W U TYPICAL PERFORM ANCE CHARACTERISTICS AND BOARD PHOTO LT1761-BYP (5V Output) 10Hz to 100Hz Output Noise Typical Dropout Voltage DC330 Board Photo 500 DROPOUT VOLTAGE (mV) 450 400 350 TJ = 125°C 300 VOUT 100µV/DIV 250 TJ = 25°C 200 150 100 50 0 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 1761 G00 IL = 100mA 1ms/DIV DC330 BP 1 DEMO MANUAL DC330 LOW DROPOUT REGULATOR W W U PACKAGE A D SCHE ATIC DIAGRA SM TOP VIEW TOP VIEW 5 OUT IN 1 GND 2 BYP 3 4 ADJ SHDN 3 S5 PACKAGE 5-LEAD PLASTIC SOT-23 TP1 VIN1 U1 LT1761-BYP 5 OUT IN C2 1µF 25V BYP ADJ TP3 GND 3 LT1761ES5-SD USER 1.22V SELECT 1.8V C1 0.01µF 4 R9 249k 1% GND 2 4 ADJ S5 PACKAGE 5-LEAD PLASTIC SOT-23 LT1761ES5-BYP 1 5 OUT IN 1 GND 2 R1 1 3 5 7 9 11 13 15 17 JP1 2V R2 118k 1% 2.5V R3 158k 1% 2.8V R4 261k 1% 3V R5 324k 1% 3.3V R6 365k 1% 5V R7 422k 1% R8 768k 1% 2 4 6 8 10 12 14 16 18 TP2 VOUT1 C3 10µF TAIYO YUDEN TP4 GND CommConn Con. Inc. 6351-18P1 1 TP5 VIN2 JP2 TP8 SHDN C4 1µF 25V USER 1.22V SELECT 1.8V U2 LT1761-SD 5 OUT IN R10 3 SHDN ADJ GND 2 4 R18 249k 1% 1 3 5 7 9 11 13 15 17 JP3 R11 118k 1% 2V 2.5V R12 158k 1% 2.8V R13 261k 1% 3V R14 324k 1% 3.3V R15 365k 1% 5V R16 422k 1% 2 4 6 8 10 12 14 16 18 Figure 1. 100mA Low Noise LDO Regulator 2 C5 4.7µF 6.3V TAIYO YUDEN TP7 GND DC330 F01 CommConn Con. Inc. 6351-18P1 R17 768k 1% TP6 VOUT2 DEMO MANUAL DC330 LOW DROPOUT REGULATOR PARTS LIST REFERENCE DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE C1 1 0402YC103KAT2A 0.01µF 16V 10% X7R Capacitor AVX (843) 946-0362 C2, C4 C3 2 1 GRM40Y5U105Z025AL LMK325BJ106MN-T 1µF 25V 80% Ceramic Capacitor 10µF 25V XX% Ceramic Capacitor Murata Erie Taiyo Yuden (770) 436-1300 (408) 573-4150 C5 JP1, JP3 1 2 JMK212BJ475MG-T 50971 4.7µF 6.3V 20% X7R Capacitor 1mm Ctr Double Row Header Taiyo Yuden Comm Con (408) 573-4150 (626) 301-4200 JP2 JP1, JP3 1 2 2802S-02G2 CTAIJ1MM-G 2mm 2-Pin Ctr. Jumper 1mm Single Insulated Shunts Comm Con Comm Con (626) 301-4200 (626) 301-4200 R1, R10 Optional R2, R11 0 2 CJ06-0R0JM CR05-1183FM 0Ω 5% 0.1W Chip Resistor 118k 1% 1/16W Chip Resistor AAC AAC (800) 508-1521 (800) 508-1521 R3, R12 R4, R13 2 2 CR05-1583FM CR05-2613FM 158k 1% 1/16W Chip Resistor 261k 1% 1/16W Chip Resistor AAC AAC (800) 508-1521 (800) 508-1521 R5, R14 R6, R15 2 2 CR05-3243FM CR05-3653FM 324k 1% 1/16W Chip Resistor 365k 1% 1/16W Chip Resistor AAC AAC (714) 255-9186 (714) 255-9186 R7, R16 R8, R17 2 2 CR05-4223FM 422k 1% 1/16W Chip Resistor 768k 1% 1/16W Chip Resistor AAC Panasonic (714) 255-9186 (714) 373-7334 R9, R18 TP1-TP8 2 8 2308-2 249k 1% 1/16W Chip Resistor Turret, Testpoint AAC Mill-Max (714) 255-9186 (516) 922-6000 U1 U2 1 1 LT1761-BYP LT1761-SD LDO Regulator IC LDO Regulator IC LTC LTC (408) 432-1900 (408) 432-1900 3 DEMO MANUAL DC330 LOW DROPOUT REGULATOR U OPERATIO Part Selection Output Capacitor Selection Two versions of the LT1761 are provided for evaluation. Both are adjustable versions, one with the low noise option, and the other with the low current shutdown option. Both allow selection of a number of common output voltages or a custom output voltage. Fixed voltage parts operate similarly to the adjustable parts, except that fixed voltage LT1761 regulators feature both low current shutdown and low noise operation. The output capacitor C3 is a 10µF X7R ceramic chip capacitor and C5 is a 3.3µF X7R ceramic chip capacitor. Care must be exercised in the selection of output capacitors should a different output capacitor be desired. Many ceramic capacitor dielectrics exhibit undesirable temperature and voltage characteristics that reduce their effective capacitance to as low as 10% to 20% of nominal value. For further information, see Linear Technology Application Note 83, “Performance Verification of Low Noise, Low Dropout Regulators,” Appendix B, “Capacitor Selection Considerations”; see also the Applications Information Section of this manual. Hook-Up Solid turret terminals are provided for easy connection to supplies and test equipment. Connect a 0V to 20V, 0.2A power supply across the VIN and GND terminals and the load across the VOUT and GND terminals. The SHDN pin can be disconnected from VIN by removing JP2 to allow separate shutdown control via a secondary control line. JP1 and JP3 can be used to select a number of common fixed output voltages or, in conjunction with R1 or R10, to create a custom output voltage using the formula: R1 or R10 = (VOUT – 1.22V)/4.93µA Output Voltage Noise Measuring output voltage noise can be a tricky process, further complicated by the low levels of noise inherent in a circuit such as this. Consideration must be given to regulator operating conditions, as well as the noise bandwidth of interest. Linear Technology has invested an enormous amount of time to provide accurate, relevant data to customers regarding noise performance. For further information on measuring output voltage noise, see Linear Technology Application Note 83, “Performance Verification of Low Noise, Low Dropout Regulators.” U W U U APPLICATIO S I FOR ATIO Noise Testing Considerations What noise bandwidth is of interest and why is it interesting? In most systems, the range of 10Hz to 100kHz is the information signal processing area of concern. Additionally, linear regulators produce little noise energy outside this region.1 These considerations suggest a measurement bandpass of 10Hz to 100kHz, with steep slopes at the band limits. Figure 2 shows a conceptual filter for LDO noise testing. The Butterworth sections are the key to steep slopes and flatness in the passband. The small input level requires 60dB of low noise gain to provide adequate signal for the Butterworth filters. Figure␣ 3 details the filter scheme. The regulator under test is at the diagram’s center.2 A1–A3 make up a 60dB gain highpass section. A1 and A2, extremely low noise devices (<1nV/√Hz), com- 4 prise a 60dB gain stage with a 5Hz highpass input. A3 provides a 10Hz, 2nd order Butterworth highpass characteristic. The LTC®1562 filter block is arranged as a 4th order Butterworth lowpass. Its output is delivered via the 330µF-100Ω highpass network. The circuit’s output drives a thermally responding RMS voltmeter.3 Note that all circuit power is furnished by batteries, precluding ground loops from corrupting the measurement. Note 1: Switching regulators are an entirely different proposition, requiring very broadband noise measurement. See Reference 1. Note 2: Component choice for the regulator, more critical than might be supposed, is discussed in Appendix B, “Capacitor Selection Considerations.” Note 3: The choice of the RMS voltmeter is absolutely crucial to obtaining meaningful measurements. See Application Note 83 Appendix C, “Understanding and Selecting RMS Voltmeters.” DEMO MANUAL DC330 LOW DROPOUT REGULATOR U W U U APPLICATIO S I FOR ATIO 5Hz SINGLE ORDER HIGHPASS 10Hz 2nd ORDER BUTTERWORTH HP GAIN = 60dB IN 100kHz 4th ORDER BUTTERWORTH LP 5Hz SINGLE ORDER HIGHPASS 10Hz TO 100kHz AN83 F01 Figure 2. Filter Structure for Noise Testing LDOs. Butterworth Sections Provide Appropriate Response in Desired Frequency Range EXTERNAL INPUT + + 330µF + INPUT 100Ω 100Ω A1 LT1028 4.5V 4.7µF 4.7µF A2 LT1028 + NORMAL INPUT – – 6.19k 3.16k 4.99k – 2k 2.49k 5.9K A3 LT1224 –4.5V VIN IN 1µF 5VOUT OUT LT1761-5 0.01µF + 10µF SHDN BYP GND RLOAD (TYPICALLY 100mA) TYPICAL REGULATOR UNDER TEST 10k 10k 1 20 5.62k 2 19 13k 10k 3 18 10k 4 17 5 16 6 15 7 14 110k 8 13 110k 17.8k 9 12 43.2k 10 11 –4.5V 4.5V 110k LTC1562 –4.5V OUTPUT TO THERMALLY RESPONDING RMS VOLTMETER 0.1V FULL SCALE = 100µVRMS NOISE 10Hz TO 100kHz BW 330µF 100Ω + ALL RESISTORS 1% METAL FILM 4.7µF CAPACITORS = MYLAR, WIMA MKS-2 330µF CAPACITORS = SANYO OSCON ±4.5V DERIVED FROM 6AA CELLS POWER REGULATOR FROM APPROPRIATE NUMBER OF D SIZE BATTERIES 110k AN83 F02 Figure 3. Implementation of Figure 2. Low Noise Amplifiers Provide Gain and Initial Highpass Shaping. LTC1562 Filter Supplies 4th Order Butterworth Lowpass Characteristic 5 DEMO MANUAL DC330 LOW DROPOUT REGULATOR U W U U APPLICATIO S I FOR ATIO APPENDIX B CAPACITOR SELECTION CONSIDERATIONS Bypass Capacitance and Low Noise Performance Adding a capacitor between the regulator’s OUT and BYP pins lowers output noise. A good quality low leakage capacitor is recommended. This capacitor bypasses the regulator’s reference, providing a low frequency noise pole. A 0.01µF capacitor lowers the output voltage noise to 20µVRMS. Using a bypass capacitor also improves transient response. With no bypassing and a 10µF output capacitor, a 10mA to 500mA load step settles to within 1% of final value in under 100µs. With a 0.01µF bypass capacitor, the output settles to within 1% for the same load step in under 10µs; total output deviation is inside 2.5%. Regulator start-up time is inversely proportional to bypass capacitor size, slowing to 15ms with a 0.01µF bypass capacitor and 10µF at the output. Output Capacitance and Transient Response The regulators are designed to be stable with a wide range of output capacitors. Output capacitor ESR affects stability, most notably with small capacitors. A 3.3µF minimum output value with ESR of 3Ω or less is recommended to prevent oscillation. Transient response is a function of output capacitance. Larger values of output capacitance decrease peak deviations, providing improved transient response for large load current changes. Bypass capacitors, used to decouple individual components powered by the regulator, increase the effective output capacitor value. Larger values of reference bypass capacitance dictate larger output capacitors. For 100pF of bypass capacitance, 4.7µF of output capacitor is recommended. With 1000pF of bypass capacitance or larger, a 6.8µF output capacitor is required. Figure B1’s shaded region defines the regulator’s stability range. Minimum ESR needed is set by the amount of bypass capacitance used, while maximum ESR is 3Ω. Ceramic Capacitors Ceramic capacitors require extra consideration. They are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics provide high capacitance in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures B2 and B3. Used with a 5V regulator, a 10µF Y5V capacitor shows values as low as 1µF to 2µF over the operating temperature range. The X5R and X7R dielectrics have more stable characteristics and are more suitable for output capacitor use. The X7R type has better stability over temperature, while the X5R is less expensive and available in higher values. 4.0 20 STABLE REGION 2.5 2.0 CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP > 3300pF 1.5 1.0 0.5 1 X5R –20 –40 –60 Y5V –80 0 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (µF) AN83 FB01 Figure B1. Regulator Stability for Various Output and Bypass (CBYP) Capacitor Characteristics 6 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF 0 3.0 CHANGE IN VALUE (%) OUTPUT CAPACITOR ESR (Ω) 3.5 –100 0 2 4 8 6 10 12 DC BIAS VOLTAGE (V) 14 16 AN83 FB02 Figure B2. Ceramic Capacitor DC Bias Characteristics Indicate Pronounced Voltage Dependence. Device Must Provide Desired Capacitance Value at Operating Voltage DEMO MANUAL DC330 LOW DROPOUT REGULATOR U W U U APPLICATIO S I FOR ATIO Voltage and temperature coefficients are not the only problem sources. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure␣ B4’s trace in response to light tapping from a pencil. Similar vibration-induced behavior can masquerade as increased output voltage noise. 40 CHANGE IN VALUE (%) 20 X5R 0 –20 –40 20µV/DIV Y5V –60 –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF –100 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 200ms/DIV 125 AN83 FB04.tif AN83 FB03 Figure B3. Ceramic Capacitor Temperature Characteristics Show Large Capacitance Shift. Effect Should Be Considered When Determining Circuit Error Budget Figure B4. A Ceramic Capacitor Responds to Light Pencil Tapping. Piezoelectric Based Response Approaches 80µVP-P U W PCB LAYOUT A D FIL Silkscreen Top Paste Mask Top Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. Component Side 7 DEMO MANUAL DC330 LOW DROPOUT REGULATOR U W PCB LAYOUT A D FIL Solder Mask Top Solder Side Solder Mask Bottom U PC FAB DRAWI G 2.250 NOTES: UNLESS OTHERWISE SPECIFIED 1. MATERIAL: 2 LAYERS, O.O62" THK. FR-4 GLASS EPOXY, 2 0Z COPPER CLAD 2. ALL HOLES SHALL BE PLATED THRU. 3. PLATE THRU HOLES WITH COPPER 0.0014 MIN THICKNESS. ALL HOLE SIZES IN HOLE TABLE ARE AFTER PLATING. 4. SILKSCREEN: WITH WHITE EPOXY NON-CONDUCTIVE INK. 5. NO SILKSCREEN ALLOWED ON PADS LANDS. 6. SOLDER MASK: LPI, GREEN. 7. NO BLOCK SOLDERMASKING OF PAD ROWS. 8. SCORING: D A C C B 2.500 A 0.020 0.017 D 8 Linear Technology Corporation NUMBER SYMBOL DIAMETER OF HOLES PLATED 0.010 YES A 8 0.035 YES B 2 0.061 YES C 8 0.070 NO D 2 20 TOTAL HOLES dc330 LT/TP 0301 500 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 2001