DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR LT1762/LT1962 150mA and 300mA Low Noise Micropower LDO Regulators DESCRIPTIO U Demonstration circuits DC339-A/DC339-B are low noise micropower voltage regulators using the LT®1762 and LT1962 in the 8-lead MSOP package. These circuits are primarily used in cellular phones, voltage-controlled oscillators and RF power supplies, and as local regulators in larger systems. Their ability to tolerate a wide variety of output capacitors makes them ideal in spaceand cost-sensitive systems. , LTC and LT are registered trademarks of Linear Technology Corporation. W U WW PERFOR A CE SU ARY TA = 25°C, VIN = 2.3V, VSHDN = 5V, ILOAD = 1mA, VOUT = 1.22V (JP2 set on pins 1 and 2), unless otherwise specified. PARAMETER CONDITIONS MIN VIN = 3.5V, JP2 On Pins 5, 6 VIN = 4V, JP2 On Pins 7, 8 VIN = 4.3V, JP2 On Pins 9, 10 VIN = 5V, JP2 On Pins 11, 12 1.205 2.455 2.936 3.207 4.848 Input Voltage Range TYP MAX 20 V 1.220 2.506 3.019 3.300 5.006 1.235 2.571 3.103 3.396 5.167 V V V V V 2.3 Output Voltage (Note 1) UNITS Line Regulation ∆VIN = 2.3V to 20V 1 5 mV Quiescent Current ILOAD = 0 30 50 µA 0.2 1 % 0.65 0.8 1.8 V V Load Regulation ∆ILOAD = 1mA to 150mA (DC339-A) or 300mA (DC339-B) SHDN Pin Threshold On to Off Off to On, ILOAD = 150mA (DC339-A) or 300mA (DC339-B) Output Voltage Noise 0.45 ILOAD = 150mA (DC339-A) or 300mA (DC339-B) BW = 10Hz to 100kHz 20 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. W U U TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO LT1762 Typical Dropout Voltage LT1762 (5V Output) 10Hz to 100kHz Output Noise 500 Component Side DROPOUT VOLTAGE (mV) 450 400 350 TJ = 125°C 300 VOUT 100µV/DIV 250 200 TJ = 25°C 150 100 50 0 0 20 40 60 80 100 120 140 160 LOAD CURRENT (mA) COUT = 10µF IL = 150mA 1ms/DIV 1762 G47 1762 G01 1 DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR W U U TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO LT1962 Typical Dropout Voltage LT1962 (5V Output) 10Hz to 100kHz Output Noise 400 Component Side DROPOUT VOLTAGE (mV) 350 TJ = 125°C 300 250 200 VOUT 100µV/DIV TJ = 25°C 150 100 50 0 0 50 100 200 250 150 OUTPUT CURRENT (mA) COUT = 10µF IL = 300mA 300 1ms/DIV 1962 G47 1962 G01 U W W PACKAGE A D SCHE ATIC DIAGRA S TOP VIEW OUT SENSE/ADJ* BYP GND 8 7 6 5 1 2 3 4 IN NC NC SHDN MS8 PACKAGE 8-LEAD PLASTIC MSOP LT1762EMS8 LT1962EMS8 U1 LT1762/ LT1962EMS8 8 E1 IN JP1 E2 SHDN C1 1µF 0603 7 6 5 IN OUT NC ADJ NC BYP SHDN GND USER SELECT 1.22V 1 2 3 2.5V C2 0.01µF 3V R1 261k ADJ1 3.3V R2 365k 5V R3 422k R4 768k 4 2 1 4 3 6 5 JP2 8 7 10 9 12 11 DC339 F01 NOTE: UNLESS OTHERWISE SPECIFIED 1. THERE ARE TWO TYPES OF ASSEMBLY: DC339-A, LT1762, 150mA DC339-B, LT1962, 300mA R5 249k Figure 1. LT1762/LT1962 150mA/300mA Low Noise Micropower LDO Regulator 2 C3 10µF 10V 1210 E3 OUT E4 GND DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR PARTS LIST REFERENCE DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE ADJ1 0 C1 1 0603ZG105ZAT1A Optional Resistor 1µF 10V Y5V Chip Capacitor AVX (843) 946-0362 C2 1 0402ZG104ZAT1A 0.1µF 10V Y5V Chip Capacitor AVX (843) 946-0362 C3 1 LMK325BJ106MN 10µF 10V X7R Chip Capacitor Taiyo-Yuden (408) 573-4150 E1 to E4 4 2308-2 Pad Turret Mill-Max (516) 922-6000 JP1 0 JP2 1 6351-12G1 Connector, SMT2X6, 0.39" Gap Comm-Con (626) 301-4200 Shunts for JP1 and JP2 2 CTAIJ1MM-G Shunts for 0.39" Gap Comm-Con (626) 301-4200 R1 1 CR05-2613FM 261k 1/16W 1% Chip Resistor AAC (800) 508-1521 R2 1 CR05-3653FM 365k 1/16W 1% Chip Resistor AAC (800) 508-1521 R3 1 CR05-4223FM 422k 1/16W 1% Chip Resistor AAC (800) 508-1521 R4 1 CR05-7683FM 768k 1/16W 1% Chip Resistor AAC (714) 255-9186 R5 1 CR05-2493FM 249k 1/16W 1% Chip Resistor AAC (714) 255-9186 U1 1 LT1762EMS8 or LT1962EMS8 8-Lead MSOP IC Version -A 8-Lead MSOP IC Version -B LTC (408) 432-1900 Optional Jumper U OPERATIO HOOK-UP Solid turret terminals are provided for easy connection to supplies and test equipment. Connect a 0V to 20V, 0.5A power supply across the IN and GND terminals and the load across the OUT and GND terminals. The SHDN pin can be disconnected from IN via JP1 to allow for separate shutdown control via a secondary control line. JP2 can be used to select any of a number of common fixed output voltages, or used in conjunction with ADJ1 to create a custom output voltage using the formula: ADJ1 = (VOUT – 1.22V)/4.93µA OUTPUT CAPACITOR SELECTION The output capacitor C3 is a 10µF X7R ceramic chip capacitor. Should a different output capacitor be desired, care must be exercised with the selection. Many ceramic capacitor dielectrics exhibit strong temperature and voltage characteristics that reduce their effective capacitance to as low as 10% to 20% of nominal over the full range. For further information, see Linear Technology Application Note 83, “Performance Verification of Low Noise, Low Dropout Regulators,” Appendix␣ B, “Capacitor Selection Considerations,” reprinted below. CAPACITOR SELECTION CONSIDERATIONS Bypass Capacitance and Low Noise Performance Adding a capacitor between the regulator’s VOUT 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 within 1% of final value in under 100µs. With a 0.01µF bypass capacitor, the output settles 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. 3 DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR U OPERATIO 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 or more of bypass capacitance, a 6.8µF output capacitor is required. The shaded regions of Figures B1 and B2 define 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 B3 and B4. 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. 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 can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure␣ B5’s trace in response to light tapping from a pencil. Similar vibration-induced behavior can masquerade as increased output voltage noise. 4.0 4.0 3.5 3.5 3.0 3.0 STABLE REGION STABLE REGION 2.5 ESR (Ω) ESR (Ω) 2.5 2.0 1.5 0.5 CBYP = 330pF CBYP ≥ 1000pF 1.0 0.5 0 0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (µF) DC339 B1 Figure B1. LT1762 Regulator Stability for Various Output and Bypass (CBYP) Capacitor Characteristics 4 CBYP = 0 CBYP = 100pF 1.5 CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP ≥ 3300pF 1.0 2.0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (µF) DC339 B2 Figure B2. LT1962 Regulator Stability for Various Output and Bypass (CBYP) Capacitor Characteristics DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR U OPERATIO 20 OUTPUT VOLTAGE NOISE BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF 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.” CHANGE IN VALUE (%) 0 X5R –20 –40 –60 Y5V –80 –100 0 2 4 14 8 6 10 12 DC BIAS VOLTAGE (V) 16 DC339 B3 Figure B3. Ceramic Capacitor DC Bias Characteristics Indicate Pronounced Voltage Dependence. Device Must Provide Desired Capacitance Value at Operating Voltage 40 CHANGE IN VALUE (%) 20 X5R 0 –20 –40 Y5V –60 –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF –100 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 DC339 B4 Figure B4. Ceramic Capacitor Temperture Characteristics Show Large Capacitance Shift. Effect Should Be Considered When Determining Circuit Error Budget 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), comprise 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. Note 2: Component choice for the regulator, more critical than might be supposed, is discussed in “Capacitor Selection Considerations.” Note 3: The choice of the RMS voltmeter is absolutely crucial to obtaining meaningful measurements. See Appendix C, Application Note 83 “Understanding and Selecting RMS Voltmeters.” 20µV/DIV 20µV/DIV Noise Testing Considerations DC339 B5 Figure B5. A Ceramic Capacitor Responds to Light Pencil Tapping. Piezoelectric Based Response Approaches 80µVP-P 5 DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR U OPERATIO 5Hz SINGLE ORDER HIGHPASS 10Hz 2nd ORDER BUTTERWORTH HP GAIN = 60dB IN 100kHz 4th ORDER BUTTERWORTH LP 5Hz SINGLE ORDER HIGHPASS 10Hz TO 100kHz DC339 F02 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 LT1762-5 0.01µF + 10µF SHDN BYP GND RLOAD (TYPICALLY 150mA) 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 DC339 F03 Figure 3. Implementation of Figure 2. Low Noise Amplifiers Provide Gain and Initial Highpass Shaping. LTC1562 Filter Supplies 4th Order Butterworth Lowpass Characteristic 6 DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR U W PCB LAYOUT A D FIL Component Side Silkscreen Component Side Component Side Solder Mask Component Side Paste Mask Solder Side Solder Side Solder Mask 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. 7 DEMO MANUAL DC339-A/-B LOW DROPOUT REGULATOR U PC FAB DRAWI G 2.00 C A B B A B A 2.00 B NOTES: UNLESS OTHERWISE SPECIFIED 1. MATERIAL: FR4 OR EQUIVALENT EPOXY, 2 OZ COPPER CLAD, THICKNESS 0.062 ±0.006 TOTAL OF 2 LAYERS 2. FINISH: ALL PLATED HOLES 0.001 MIN/0.0015 MAX COPPER PLATE, ELECTRODEPOSITED TIN-LEAD COMPOSITION BEFORE REFLOW, SOLDER MASK OVER BARE COPPER (SMOBC) 3. SOLDER MASK: BOTH SIDES USING LPI OR EQUIVALENT 4. SILKSCREEN: USING WHITE NONCONDUCTIVE EPOXY INK 5. UNUSED SMD COMPONENTS SHOULD BE FREE OF SOLDER 6. FILL UP ALL VIAS WITH SOLDER 7. SCORING 0.017 C SYMBOL DIAMETER NUMBER OF HOLES PLATED A 0.020 11 PLTD B 0.060 4 PLTD C 0.070 2 NPLTD TOTAL HOLES 17 DC339 FD 8 Linear Technology Corporation dc339 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