LTC3035 - 300mA VLDO Linear Regulator with Charge Pump Bias Generator

LTC3035
300mA VLDO Linear
Regulator with Charge Pump
Bias Generator
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FEATURES
DESCRIPTIO
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The LTC®3035 is a micropower, VLDO™ (very low dropout) linear regulator which operates from input voltages as
low as 1.7V. The device is capable of supplying 300mA of
output current with a typical dropout voltage of only
45mV. To allow operation at low input voltages the LTC3035
includes a charge pump generator that provides the necessary bias voltage for the internal LDO circuitry. Output
current comes directly from the input supply for high
efficiency regulation. The charge pump bias generator
requires only a 0.1µF flying capacitor and a 1µF bypass
capacitor for operation. The low 0.4V internal reference
voltage allows the LTC3035 to be programmed to much
lower output voltages than commonly available in LDOs.
The output voltage is programmed via two tiny SMD
resistors. The LTC3035’s low quiescent current makes it
an ideal choice for use in battery-powered systems.
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Wide Input Voltage Range: 1.7V to 5.5V
Wide Adjustable Output Voltage Range:
0.4V to 3.6V
Built-In Charge Pump Generates High Side Bias
Very Low Dropout: 45mV at 300mA
± 2% Voltage Accuracy Over Temperature,
Supply, Load
Fast Transient Recovery
Low Operating Current: IIN = 100µA Typ
Low Shutdown Current: IIN = 1µA Typ
Stable with Ceramic Capacitor Down to 1µF
Output Current Limit
Thermal Overload Protected
Reverse Output Current Protected
Available in 8-Lead (3mm × 2mm) DFN Package
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APPLICATIO S
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Li-Ion to 3.3V Low Dropout Supplies
2 × AA to 1.8V Low Dropout Supplies
Low Power Handheld Devices
Low Voltage Logic Supplies
DSP Power Supplies
Cellular Phones
Portable Electronic Equipment
Handheld Medical Instruments
Post Regulator for Switching Supply Noise Rejection
Other features include high output voltage accuracy, excellent transient response, stability with ultralow ESR
ceramic capacitors as small as 1µF, short-circuit and
thermal overload protection, output current limiting and
reverse output current protection. The LTC3035 is available in a tiny, low profile (3mm × 2mm × 0.75mm) 8-lead
DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
VLDO is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6411531, others pending.
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TYPICAL APPLICATIO
0.1µF
60
CM
IN
1µF
0.4V
BIAS
GENERATOR
+
–
SHDN
CBIAS
1µF
OUT
LTC3035
OFF ON
BIAS
GND
ADJ
294k
40.2k
3035 TA01a
VOUT
3.3V
COUT 300mA
1µF
DROPOUT VOLTAGE (mV)
70
CP
Li-Ion
BATTERY
3.4V TO 4.2V
Dropout Voltage vs Load Current
3.3V Output Voltage from Li-Ion Battery
TA = 25°C
50
40
30
20
10
0
0
50
100
200
150
IOUT (mA)
250
300
3035 TA01b
3035f
1
LTC3035
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Notes 1, 2)
TOP VIEW
VIN to GND .................................................. – 0.3V to 6V
SHDN to GND ............................................. – 0.3V to 6V
CP, CM, BIAS to GND ................................. – 0.3V to 6V
ADJ to GND ................................................ – 0.3V to 6V
VOUT to GND ............................................... – 0.3V to 6V
Operating Junction Temperature
(Note 3) ........................................... – 40°C to 125°C
Storage Temperature Range ................ – 65°C to 125°C
Output Short Circuit Duration .......................... Indefinite
CP 1
CM 2
GND 3
9
IN 4
8
BIAS
7
SHDN
6
ADJ
5
OUT
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) IS GND,MUST BE SOLDERED TO PCB
ORDER PART NUMBER
LTC3035EDDB
DDB PART MARKING
LBRM
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full specified temperature
range, otherwise specifications are at TA = 25°C. VIN = 3.6V, VOUT = 3.3V, CFLY = 0.1µF, COUT = 1µF, CIN = 1µF, CBIAS = 1µF (all
capacitors ceramic) unless otherwise noted.
PARAMETER
VIN Operating Voltage (Note 4)
VBIAS Output Voltage Range
VOUT Output Voltage Range
VIN Operating Current
VIN Shutdown Current
VADJ Regulation Voltage (Note 5)
IADJ ADJ Input Current
OUT Load Regulation (Referred to ADJ Pin)
Dropout Voltage (Note 6)
IOUT Continuous Output Current
IOUT Short Circuit Output Current
VOUT Output Noise Voltage
VIH SHDN Input High Voltage
VIL SHDN Input Low Voltage
IIH SHDN Input High Current
IIL SHDN Input Low Current
CONDITIONS
●
●
●
2.63V < VIN < 5.5V
1.7V < VIN < 2.63V
●
IOUT = 10µA
VSHDN = 0V
1mA < IOUT < 300mA, 1.7V < VIN < 5.5V,
VOUT = 1.5V
VADJ = 0.4V
IOUT = 1mA to 300mA
VIN = 1.7V, VADJ = 0.37V, IOUT = 300mA
MIN
1.7
4.8
1.85 • VIN
VADJ
●
●
0.392
●
–50
●
●
100
1
0.4
0
–0.2
45
UNITS
V
V
V
V
µA
µA
V
50
nA
mV
mV
mA
mA
µVrms
V
V
µA
µA
100
760
150
●
1.1
●
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
5
1.90 • VIN
MAX
5.5
5.3
1.95 • VIN
3.6
200
5
0.408
300
VADJ = VOUT = 0
F = 10Hz to 100kHz, IOUT = 150mA
SHDN = VIN
SHDN = 0V
TYP
–1
–1
0.3
1
1
Note 3: The LTC3035 regulator is tested and specified under pulse load
conditions such that TJ ≈ TA. The LTC3035 is 100% production tested at
25°C. Performance at –40°C and 125°C is assured by design,
characterization and correlation with statistical process control.
Note 4: Min Operating Input Voltage required for regulation is:
VIN > VOUT + VDROPOUT and VIN > 1.7V
3035f
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LTC3035
ELECTRICAL CHARACTERISTICS
Note 5: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must
be limited.
Note 6: Dropout voltage is minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to VIN – VDROPOUT.
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TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage vs Load Current
VIN Shutdown Current
4.5
60
50
110
TA = 125°C
105
3.5
40
TA = 25°C
30
TA = 85°C
3.0
IIN (µA)
TA = 125°C
2.5
2.0
TA = –40°C
TA = –40°C
0
50
100
200
150
IOUT (mA)
0
300
250
1
2
3
VIN (V)
80
4
404
TA = 125°C
ADJUST VOLTAGE (mV)
TA = 85°C
100
TA = 25°C
80
TA = –40°C
70
60
0
1
2
3
VIN (V)
4
5
6
3035 G04
3.5
4
4.5
VIN (V)
5
ADJ Voltage vs Input Voltage
404
VOUT = 3.3V
403
403
402
402
401
400
399
400
399
398
397
397
15 35 55 75
TEMPERATURE (°C)
95 115
3035 G05
VOUT = 1.5V
401
398
396
–45 –25 –5
6
5.5
3035 G03
ADJ VOLTAGE (mV)
VOUT = 1.5V
90
3
ADJ Voltage vs Temperature
VIN No Load Operating Current
110
6
5
LT1108 • TPC12
3035 G01
120
TA = –40°C
85
0.5
0
TA = 25°C
95
90
TA = 25°C
1.0
0
100
TA = 85°C
1.5
20
10
IIN (µA)
VOUT = 3.3V
4.0
IIN (µA)
DROPOUT VOLTAGE (mV)
VIN No Load Operating Current
115
5.0
70
396
0
1
2
3
VIN (V)
4
5
6
3035 G06
3035f
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LTC3035
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TYPICAL PERFOR A CE CHARACTERISTICS
SHDN Threshold (Rising)
vs Temperature
6
1000
5
900
4
3
2
1
0
SHDN Threshold (Falling)
vs Temperature
1000
900
VIN = 5.5V
SHDN THRESHOLD (mV)
SHDN THRESHOLD (mV)
BIAS VOLTAGE (V)
BIAS Voltage vs Input Voltage
800
VIN = 3.6V
700
VIN = 1.7V
600
400
–45
–20
55
30
5
80
TEMPERATURE (°C)
3035 G07
105
VIN = 1.7V
600
400
–45
130
–20
55
30
5
80
TEMPERATURE (°C)
105
130
3035 G09
3035 G08
VIN Ripple Rejection vs Frequency
Current Limit vs Input Voltage
900
VIN = 3.6V
700
500
500
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
VIN (V)
VIN = 5.5V
800
70
VOUT = 0V
800
60
COUT = 10µF
50
600
REJECTION (dB)
CURRENT LIMIT (mA)
700
500
400
300
40
30
COUT = 1µF
20
200
10
100
0
1.5
2
2.5
3
3.5
4
4.5
5
5.5
VIN = 3.6V
VOUT = 3.3V
IOUT = 100mA
0
100
1k
VIN (V)
10k
100k
3035 G10
BIAS Output Ripple
VOUT
20mV/DIV
AC
VBIAS
50mV/DIV
AC
300mA
VOUT
5mV/DIV
AC
10mA
VIN = 3.6V
VOUT = 3.3V
COUT = 1µF
200µs/DIV
10M
3035 G13
Transient Response
IOUT
1M
FREQUENCY (Hz)
3035 G11
VIN = 3.6V
VOUT = 3.3V
CBST = 1µF
CFLY = 0.1µF
COUT = 1µF
IOUT = 1mA
500µs/DIV
3035 G12
3035f
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LTC3035
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PI FU CTIO S
CP (Pin 1): Flying Capacitor Positive Terminal.
ADJ (Pin 6): Adjust Input Pin. This is the input to the error
amplifier. The ADJ pin reference voltage is 0.4V referenced
to ground. The output voltage range is 0.4V to 3.6V and is
set by connecting ADJ to a resistor divider from OUT to
GND.
CM (Pin 2): Flying Capacitor Negative Terminal.
GND (Pin 3): Ground. Connect to a ground plane.
IN (Pin 4): Input Supply Voltage. The output load current
is supplied directly from IN. The IN pin should be locally
bypassed to ground if the LTC3035 is more than a few
inches away from another source of bulk capacitance. In
general, the output impedance of a battery rises with
frequency, so it is usually adviseable to include an input
bypass capacitor when supplying IN from a battery. A
capacitor of 1µF is usually sufficient.
SHDN (Pin 7): Shutdown Input, Active Low. This pin is
used to put the LTC3035 into shutdown. The SHDN pin
current is typically less than 10nA. The SHDN pin cannot
be left floating and must be tied to a valid logic level if
not used.
BIAS (Pin 8): BIAS Output Voltage Pin. BIAS is the output
of the charge pump and provides the high side supply for
the LTC3035 LDO circuitry. This pin should be locally
bypassed to ground by a 1µF or greater capacitor as close
as possible to the pin. Nothing else should be connected
to this pin.
OUT (Pin 5): Regulated Output Voltage. The OUT pin
supplies power to the load. A minimum ceramic output
capacitor of at least 1µF is required to ensure stability.
Larger output capacitors may be required for applications
with large transient loads to limit peak voltage transients.
See the Applications Information section for more information on output capacitance.
Exposed Pad (Pin 9): Ground and Heat Sink. Must be
soldered to PCB ground plane or large pad for optimal
thermal performance.
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BLOCK DIAGRA
8
BIAS
–
5V
1.9 • VIN
4
VMIN
+
EN
800kHz
OSCILLATOR
CHARGE
PUMP
CP
CM
7
1
VIN
SHDN
SOFT-START
REFERENCE
SHDN
0.400V
+
2
BIAS
–
OUT
5
2.5k
BIAS
UVLO
GND
PINS 3, 9
ADJ
6
3035 BD
3035f
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LTC3035
(Refer to Block Diagram)
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The LTC3035 is a VLDO (very low dropout) linear regulator
which operates from input voltages between 1.7V and
5.5V. The LDO uses an internal NMOS transistor as the
pass device in a source-follower configuration. The internal charge pump generator provides the high supply
necessary for the LDO circuitry while the output current
comes directly from the IN input for high efficiency
regulation.
Charge Pump Operation
The LTC3035 contains a charge pump to produce the
necessary bias voltage supply for the LDO. The charge
pump utilizes Burst Mode operation to achieve high
efficiency for the relatively low current levels needed for
the LDO circuitry. The charge pump requires only a small
0.1µF flying capacitor between the CP and CM pins and a
1µF bypass capacitor at BIAS.
An internal oscillator centered at 800kHz controls the
two-phase switching cycle of the charge pump. During the
first phase a current source charges the flying capacitor
between VIN and GND. During the second phase, the
capacitor’s positive terminal connects to BIAS and the
current source drives the capacitor’s minus terminal,
delivering charge to the BIAS bypass capacitor and increasing its voltage.
A burst comparator with hysteresis monitors the voltage
on the BIAS pin. When BIAS is above the upper threshold
of the comparator, the oscillator is disabled and no switching occurs. When BIAS falls below the comparator’s lower
threshold, the oscillator is enabled and the BIAS pin gets
charged. The thresholds of the burst comparator are
dynamically adjusted to maintain a DC level shown by
Figure 1. BIAS regulates to 1.9 • VIN or 5V, whichever
voltage is lower. The voltage ripple at BIAS is controlled to
approximately 1% of its DC value.
LDO Operation
An undervoltage lockout comparator (UVLO) senses the
BIAS voltage to ensure that the BIAS supply for the LDO is
greater than 90% of its regulation value before
enabling the LDO. Once the LDO gets enabled, the UVLO
threshold switches to 50% of its regulation value. Thus the
BIAS voltage must fall below 50% of its regulation voltage
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1.9 • VIN
BIAS (V)
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APPLICATIO S I FOR ATIO
3.23
1.7
2.63
VIN (V)
5.5
3035 F01
Figure 1. LTC3035 BIAS Voltage vs VIN Voltage
before the LDO disables. When the LDO is disabled, OUT
is pulled to GND through the external divider and an
internal 2.5k resistor.
The LDO provides a high accuracy output capable of
supplying 300mA of output current with a typical dropout
voltage of only 45mV. A single ceramic capacitor as small
as 1µF is all that is required for output bypassing. The low
reference voltage allows the LTC3035 output to be
programmed from 0.4V to 3.6V.
As shown in the Block Diagram, the charge pump output
at BIAS supplies the LDO circuitry while the output current
comes directly from the IN input for high efficiency
regulation. The low quiescent supply current, IIN = 100µA,
drops to IIN = 1µA typical in shutdown making the LTC3035
an ideal choice for use in battery-powered systems.
The device also includes current limit, thermal overload
protection, and reverse output current protection. The fast
transient response of the follower output stage overcomes
the traditional tradeoff between dropout voltage, quiescent current and load transient response inherent in most
LDO regulator architectures. The LTC3035 also includes
overshoot detection circuitry which brings the output back
into regulation when going from heavy to light output
loads (see Figure 2).
The LTC3035 also includes a soft-start feature to prevent
excessive current flow during start-up. After the BIAS
voltage reaches regulation, the soft-start circuitry gradually increases the LDO reference voltage from 0V to 0.4V
over a period of about 600µs. There is a short 700µs delay
from the time BIAS reaches regulation until the LDO
output starts to rise (see Figure 3).
3035f
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LTC3035
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APPLICATIO S I FOR ATIO
( )
R2
VOUT = 0.4V 1 +
R1
VOUT
R2
VOUT
20mV/DIV
AC
COUT
ADJ
R1
GND
3035 F04
300mA
Figure 4. Programming the LTC3035
IOUT
0mA
VIN = 3.6V
VOUT = 3.3V
COUT = 1µF
200µs/DIV
3035 F02
Figure 2. Output Step Response
ON
SHDN
OFF
current change of 1mA to 300mA produces a – 0.2mV
drop at the ADJ input. To calculate the change refered to
the output simply multiply by the gain of the feedback
network (i.e., 1 + R2/R1). For example, to program the
output for 3.3V choose R2/R1 = 7.25. In this example an
output current change of 1mA to 300mA produces
–0.2mV • (1 + 7.25) = 1.65mV drop at the output.
Output Capacitance and Transient Response
VBIAS
2V/DIV
0V
VOUT
2V/DIV
0V
VIN = 3.6V
VOUT = 3.3V
COUT = 1µF
CBIAS = 1µF
500µs/DIV
3035 F03
Figure 3. Bias and Output Start-Up Waveforms
Adjustable Output Voltage
The output voltage is set by the ratio of two external
resistors as shown in Figure 4. The device servos the
output to maintain the ADJ pin voltage at 0.4V (referenced
to ground). Thus the current in R1 is equal to 0.4V/R1. For
good transient response, stability and accuracy the
current in R1 should be at least 8µA, thus the value of R1
should be no greater than 50k. The current in R2 is the
current in R1 plus the ADJ pin bias current. Since the ADJ
pin bias current is typically <10nA it can be ignored in the
output voltage calculation. The output voltage can be
calculated using the formula in Figure 4. Note that in
shutdown the output is turned off and the divider current
will be zero once COUT is discharged.
The LTC3035 operates at a relatively high gain of
–0.7µV/mA referred to the ADJ input. Thus a load
The LTC3035 is designed to be stable with a wide range of
ceramic output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. An
output capacitor of 1µF or greater with an ESR of 0.05Ω or
less is recommended to ensure stability. The LTC3035 is
a micropower device and output transient response will be
a function of output capacitance. Larger values of output
capacitance decrease the peak deviations and provide
improved transient response for larger load current
changes. Note that bypass capacitors used to decouple
individual components powered by the LTC3035 will
increase the effective output capacitor value. High ESR
tantalum and electrolytic capacitors may be used, but a
low ESR ceramic capacitor must be in parallel at the
output. There is no minimum ESR or maximum capacitor
size requirements.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances
in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 5 and 6. When
used with a 3.3V regulator, a 1µF Y5V capacitor can lose
as much as 80% of its rated capacitance over the operating
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LTC3035
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APPLICATIO S I FOR ATIO
20
BOTH CAPACITORS ARE 1µF,
6.3V, 0402 CASE SIZE
CHANGE IN VALUE (%)
0
–20
Y5V
X5R
–40
–60
–80
–100
0
1
4
5
3
2
DC BIAS VOLTAGE (V)
6
3035 F05
Figure 5. Ceramic Capacitor DC Bias Characteristics
20
CHANGE IN VALUE (%)
0
available current, a 0.1µF or greater ceramic capacitor
should be used. Warning: A polarized capacitor such as
tantalum or aluminum should never be used for the flying
capacitor since its voltage can reverse upon start-up of the
LTC3035. Low ESR ceramic capacitors should always be
used for the flying capacitor.
A 1µF or greater low ESR (<0.1Ω) ceramic capacitor is
recommended to bypass the BIAS pin. Larger values of
capacitance will not reduce the size of the BIAS ripple
much, but will decrease the ripple frequency proportionally. The BIAS pin should maintain 0.4µF of capacitance at
all times to ensure correct operation. High ESR tantalum
and electrolytic capacitors may be used, but a low ESR
ceramic must be used in parallel for correct operation. It
is also recommended that IN be bypassed to ground with
a 1µF or greater ceramic capacitor.
X5R
Thermal Considerations
–20
Y5V
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be the output current
multiplied by the input/output voltage differential:
–40
–60
–80
BOTH CAPACITORS ARE 1µF,
6.3V, 0402 CASE SIZE
–100
0
25
50
–50
–25
TEMPERATURE (°C)
75
3035 F06
Figure 6. Ceramic Capacitor Temperature Characteristics
temperature range. The X5R only loses about 40% of its
rated capacitance over the operating temperature range.
The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output
capacitor. The X7R type has better stability across temperature and bias voltage, while the X5R is less expensive
and is available in higher values. In all cases, the output
capacitance should never drop below 0.4µF, or instability
or degraded performance may occur.
Charge Pump Component Selection
The flying capacitor controls the strength of the charge
pump. In order for the charge pump to deliver its maximum
(IOUT)(VIN – VOUT)
The LTC3035 has internal thermal limiting designed to
protect the device during momentary overload conditions.
For continuous normal conditions, the maximum junction
temperature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat-spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through holes can also be used to spread the heat
generated by power devices.
A junction to ambient thermal coefficient of 76°C/W is
achieved by connecting the Exposed Pad of the DFN
package directly to a ground plane of about 2500mm2.
3035f
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LTC3035
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OPERATIO
Calculating Junction Temperature
Example: Given an output voltage of 1.5V, an input voltage
of 1.8V to 3V, an output current range of 0mA to 100mA
and a maximum ambient temperature of 50°C, what will
the maximum junction temperature be?
The power dissipated by the device will be approximately:
IOUT(MAX)(VIN(MAX) – VOUT)
where:
IOUT(MAX) = 100mA
VIN(MAX) = 3V
so:
P = 100mA(3V – 1.5V) = 0.15W
Even under worst-case conditions LTC3035’s BIAS pin
power dissipation is only about 1mW, thus can be
ignored. The junction to ambient thermal resistance will be
on the order of 76°C/W. The junction temperature rise
above ambient will be approximately equal to:
0.15W(76°C/W) = 11.4°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
T = 50°C + 11.4°C = 61.4°C
Short-Circuit/Thermal Protection
The LTC3035 has built-in output short-circuit current
limiting as well as over temperature protection. During
short-circuit conditions, internal circuitry automatically
limits the output current to approximately 760mA. At
higher temperatures, or in cases where internal power
dissipation causes excessive self heating on chip, the
thermal shutdown circuitry will shut down the charge
pump and LDO when the junction temperature exceeds
approximately 155°C. It will reenable the converter and
LDO once the junction temperature drops back to approximately 140°C. The LTC3035 will cycle in and out of
thermal shutdown without latch-up or damage until the
overstress condition is removed. Long term overstress
(TJ>125°C) should be avoided as it can degrade the
performance or shorten the life of the part.
Layout Considerations
Connection from the BIAS and OUT pins to their respective
ceramic bypass capacitor should be kept as short as
possible. The ground side of the bypass capacitors should
be connected directly to the ground plane for best results
or through short traces back to the GND pin of the part.
Long traces will increase the effective series ESR and
inductance of the capacitor which can degrade
performance.
The CP and CM pins of the charge pump are switching
nodes. The transition edge rates of these pins can be quite
fast (~10ns). Thus care must be taken to make sure these
nodes do not couple capacitively to other nodes (especially the ADJ pin). Place the flying capacitor as close as
possible to the CP and CM pins for optimum charge pump
performance.
Because the ADJ pin is relatively high impedance
(depending on the resistor divider used), stray capacitance at this pin should be minimized (<10pF) to prevent
phase shift in the error amplifier loop. Additional special
attention should be given to any stray capacitances that
can couple external signals onto the ADJ pin producing
undesirable output ripple. For optimum performance
connect the ADJ pin to R1 and R2 with a short PCB trace
and minimize all other stray capacitance to the ADJ pin.
Figure 7 shows an example layout for the LTC3035.
CBIAS
1 CP
BIAS 8
2 CM
SHDN 7
CF
3 GND
ADJ 6
4 IN
OUT 5
CIN
R1
R2
COUT
VIA CONNECTION
TO GND PLANE
3035 F07
Figure 7. Suggested Layout
3035f
9
LTC3035
U
TYPICAL APPLICATIO
Low Noise Li-Ion to 3.3V Supply
0.1µF
L1
10µH
3.4V
600mA
S
3
VIN = 2.7V TO 4.2V
LTC3440
VIN
S
8
Li-Ion
SW2
SW1
7
SHDN/SS
VOUT
FB
S
S
6
CBIAS
1µF
BIAS
IN
CIN
1µF
4
CM
CP
LTC3035
SHDN
OUT
S
GND
ADJ
S
R1
357k
9
294k
C1
10µF
2
*
MODE/SYNC
1
RT
60.4k
S
OFF ON
RT
VC
GND
40.2k
10
C2
22µF
S
R3
15k
5
R2
200k
S
VOUT = 3.3V
≤ 300mA
I
COUT OUT
1µF
S
C5 1.5nF
+
S
S
S
S
S
3035 TA02
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
CIN, CBIAS, COUT: TDK C1005X5R0J105K
L1: SUMIDA CDRH6D38-100
Efficiency vs Output Current
Ripple Rejection
100
90
VIN = 2.7V
EFFICIENCY (%)
80
LTC3440
OUTPUT
AC
20mV/DIV
Burst Mode®
OPERATION
70
60
50
VIN = 4.2V
40
VIN = 3.6V
30
LTC3035
OUTPUT
AC
20mV/DIV
20
10
0
0.1
10
1
100
OUTPUT CURRENT (mA)
1000
IOUT = 25mA
20µs/DIV
3035 TA02c
3035 TA02b
Burst Mode IS A REGISTERED TRADEMARK OF
LINEAR TECHNOLOGY CORPORATION
3035f
10
LTC3035
U
PACKAGE DESCRIPTIO
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 ±0.05
(2 SIDES)
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
2.20 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ±0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 ± 0.10
8
2.00 ±0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.56 ± 0.05
(2 SIDES)
0.200 REF
0.75 ±0.05
0 – 0.05
4
0.25 ± 0.05
1
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 ±0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
3035f
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.
11
LTC3035
U
TYPICAL APPLICATIO S
Dual LDO Output (1.8V, 1.5V) from 2.5V Supply Rail
VIN
2.5V
0.1µF
1µF
1µF
CP
CM
IN
BIAS
LTC3035
SHDN OUT
0.1µF
BIAS
LTC3025
SHDN OUT
IN
140k
GND
0.1µF
VOUT = 1.8V
IOUT < 300mA
110k
GND
1µF
ADJ
ADJ
40.2k
VOUT = 1.5V
IOUT < 300mA
1µF
40.2k
3035 TA03
OFF ON
Dual LDO Output (1.5V, 1.2V) from 1.8V Supply Rail
VIN
1.8V
0.1µF
1µF
1µF
CP
CM
IN
BIAS
LTC3035
SHDN OUT
0.1µF
BIAS
LTC3025
SHDN OUT
IN
110k
GND
0.1µF
VOUT = 1.5V
IOUT < 300mA
1µF
ADJ
40.2k
80k
GND
ADJ
VOUT = 1.2V
IOUT < 300mA
1µF
40.2k
3035 TA04
OFF ON
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT 1761
100mA, Low Noise Micropower, LDO
VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 20µA, ISD < 1µA, VOUT = Adj,
1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V, ThinSOTTM Package.
Low Noise < 20µVRMSP-P, Stable with 1µF Ceramic Capacitors
LT1762
150mA, Low Noise Micropower LDO
VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 25µA, ISD < 1µA, VOUT = Adj,
2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20µVRMSP-P
LT1763
500mA, Low Noise Micropower LDO
VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 30µA, ISD < 1µA, VOUT = 1.5,
1.8V, 2.5V, 3V, 3.3V, 5V, S8 Package. Low Noise < 20µVRMSP-P
LTC1844
150mA, Very Low Dropout LDO
VIN: 1.6V to 6.5V, VOUT(MIN) = 1.25V, VDO = 0.08V, IQ = 40µA, ISD < 1µA, VOUT = Adj,
1.5V, 1.8V, 2.5V, 2.8V, 3.3V, ThinSOT Package. Low Noise < 30µVRMSP-P, Stable with
1µF Ceramic Capacitors
LT1962
300mA, Low Noise Micropower LDO
VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30µA, ISD < 1µA, VOUT = 1.5,
1.8V, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20µVRMSP-P
LT3020
100mA, Low Voltage, VLDO
VIN: 0.9V to 10V, VOUT(MIN) = 0.20V, VDO = 0.15V, IQ = 120µA, ISD < 3µA, VOUT = Adj,
DFN, MS8 Package
LTC3025
300mA, Micropower VLDO Linear Regulator
VIN: 0.9V to 5.5V, VBIAS: 2.5V to 5.5V, VOUT(MIN) = 0.4V, VDO = 0.05V, IQ = 54µA,
ISD < 1µA, VOUT = Adj, DFN Package. Stable with 1µF Ceramic Capacitors
LTC3026
1.5A, Low Input Voltage VLDO Linear Regulator
VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (External 5V Boost),
VOUT(MIN) = 0.4V, VDO = 0.15V, IQ = 400µA, ISD < 1µA, VOUT = Adj,
DFN, MSOP Packages. Stable with 10µF Ceramic Capacitors
®
ThinSOT is a trademark of Linear Technology Corporation.
3035f
12
Linear Technology Corporation
LT 1105 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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© LINEAR TECHNOLOGY CORPORATION 2005