DC330A - Demo Manual

DEMO MANUAL DC330
LOW DROPOUT REGULATOR
LT1761 100mA Low Noise
Micropower LDO Regulators
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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.
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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.
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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
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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
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DEMO MANUAL DC330
LOW DROPOUT REGULATOR
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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.”
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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
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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
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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
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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
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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
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DEMO MANUAL DC330
LOW DROPOUT REGULATOR
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PCB LAYOUT A D FIL
Solder Mask Top
Solder Side
Solder Mask Bottom
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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
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