DC339A - Demo Manual

DEMO MANUAL DC339-A/-B
LOW DROPOUT REGULATOR
LT1762/LT1962
150mA and 300mA Low Noise
Micropower LDO Regulators
DESCRIPTIO
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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.
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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.
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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
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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
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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
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1
LT1762EMS8 or
LT1962EMS8
8-Lead MSOP IC Version -A
8-Lead MSOP IC Version -B
LTC
(408) 432-1900
Optional Jumper
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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.
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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
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DEMO MANUAL DC339-A/-B
LOW DROPOUT REGULATOR
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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
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DEMO MANUAL DC339-A/-B
LOW DROPOUT REGULATOR
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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
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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
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