LTC3026EDD#TRPBF [Linear]
LTC3026 - 1.5A Low Input Voltage VLDO Linear Regulator; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C;
| 型号： | LTC3026EDD#TRPBF |
| 厂家： | 
Linear |
| 描述： | LTC3026 - 1.5A Low Input Voltage VLDO Linear Regulator; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C 光电二极管 输出元件 调节器 |
| 文件： | 总16页 (文件大小：197K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3026
1.5A Low Input Voltage
VLDO Linear Regulator
FEATURES
DESCRIPTION
TheLTC®3026isaverylowdropout(VLDO™)linearregula-
tor that can operate at input voltages down to 1.14V. The
device is capable of supplying 1.5A of output current with
a typical dropout voltage of only 100mV. To allow opera-
tion at low input voltages the LTC3026 includes a boost
converter that provides the necessary headroom for the
internal LDO circuitry.
n
Input Voltage Range:
1.14V to 3.5V (with Boost Enabled)
1.14V to 5.5V (with External 5V Boost)
n
Low Dropout Voltage: 100mV at I
= 1.5A
OUT
n
n
n
n
n
n
Adjustable Output Range: 0.4V to 2.6V
Output Current: Up to 1.5A
Excellent Supply Rejection Even Near Dropout
Shutdown Disconnects Load from V and V
IN
BST
Output current comes directly from the input supply to
maximize efficiency. The boost converter requires only a
small chip inductor and ceramic capacitor for operation.
Additionally, the boosted output voltage of one LTC3026
can supply the boost voltage for other LTC3026s, thus
requiring a single inductor for multiple LDOs. A user
supplied boost voltage can be used eliminating the need
for an inductor altogether.
Low Operating Current: I = 950μA at V = 1.5V
IN
IN
Low Shutdown Current:
I < 1μA (Typ), I = 0.1μA (Typ)
IN
BST
n
n
n
n
Stable with 10μF or Greater Ceramic Capacitors
Short-Circuit, Reverse Current Protected
Overtemperature Protected
Available in 10-Lead MSOP and 10-Lead
(3mm × 3mm) DFN Packages
The LTC3026 regulator is stable with 10μF or greater
ceramic output capacitors. The device has a low 0.4V
reference voltage which is used to program the output
voltage via two external resistors. The device also has
internal current limit, overtemperature shutdown, and
reverse output current protection. The LTC3026 is avail-
able in a small 10-lead MSOP or low profile (0.75mm)
10-lead 3mm × 3mm DFN package.
APPLICATIONS
n
High Efficiency Linear Regulator
n
Post Regulator for Switching Supplies
n
Microprocessor Supply
L, LT, LTC, LTM, Linear Technology and the Linear logo 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. Patents pending.
TYPICAL APPLICATION
1.2V Output Voltage from 1.5V Input Supply
Dropout Voltage vs Output Current
150
L1
10μH
SW
BST
5V BOOST
CONVERTER
4.7μF
100
IN
0.4V
1.2V
1.5V
2.0V
2.6V
V
= 1.5V
IN
4.7μF
+
–
V
= 1.2V,
OUT
ADJ
OUT
50
0
1.5A
8.06k
C
OUT
10μF
OFF ON
SHDN
LTC3026
100k
4.02k
1.0
1.5
0
0.5
GND
PG
I
(A)
OUT
3026 TA01a
3026 TA01b
L1: MURATA LQH2MCN100K02
3026fc
1
LTC3026
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
to GND................................................. –0.3V to 6V
Operating Junction Temperature Range
BST
V to GND................................................... –0.3V to 6V
IN
(Note 8) .............................................–40°C to 125°C
Storage Temperature Range...................–65°C to 125°C
Lead Temperature (MSE, Soldering, 10 sec)......... 300°C
SHDN to GND............................................ –0.3V to 6.3V
ADJ to GND................................... –0.3V to (V + 0.3V)
IN
Output Short-Circuit Duration .......................... Indefinite
PIN CONFIGURATION
TOP VIEW
TOP VIEW
IN
IN
1
2
3
4
5
10 OUT
IN
IN
GND
SW
BST
1
2
3
4
5
10 OUT
9
8
7
6
OUT
ADJ
PG
9
8
7
6
OUT
ADJ
PG
11
GND
SW
BST
11
SHDN
SHDN
MSE PACKAGE
10-LEAD PLASTIC MSOP
= 125°C, θ = 40°C/W
JA
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
DD PACKAGE
T
JMAX
10-LEAD (3mm × 3mm) PLASTIC DFN
= 125°C, θ = 40°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
JA
ORDER INFORMATION
LEAD FREE FINISH
LTC3026EDD#PBF
LTC3026EMSE#PBF
LEAD BASED FINISH
LTC3026EDD
TAPE AND REEL
PART MARKING
LBHW
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3026EDD#TRPBF
LTC3026EMSE#TRPBF
TAPE AND REEL
–40°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
LTBJB
PART MARKING
LBHW
PACKAGE DESCRIPTION
LTC3026EDD#TR
LTC3026EMSE#TR
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
LTC3026EMSE
LTBJB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
3026fc
2
LTC3026
ELECTRICAL CHARACTERISTICS (BOOST ENABLED, LSW = 10μH)
The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at
TA = 25°C. VIN = 1.5V, VOUT = 1.2V, CIN = CBST = 4.7μF, COUT = 10μF (all capacitors ceramic) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
V
Operating Voltage
Operating Current
(Note 2)
1.14
3.5
V
IN
I
IN
I
I
I
I
= 0mA, V
= 0mA, V
= 0mA, V
= 0mA, V
= 0.8V, V
= 1.2V, V
= 1.2V, V
= 1.2V, V
= V , V = 1.2V
1160
950
640
400
μA
μA
μA
μA
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
SHDN
SHDN
SHDN
SHDN
IN IN
= V , V = 1.5V
IN IN
= V , V = 2.5V
IN IN
= V , V = 3.5V
IN IN
l
I
Shutdown Current
V
SHDN
= 0V, V = 3.5V
0.6
10
20
40
μA
INSHDN
IN
Inductor Size Requirement
Inductor Peak Current Requirement
4.7
150
μH
mA
V
V
Boost Output Voltage Range
Boost Undervoltage Lockout
Boost Output Drive (Note 3)
V
= V
4.8
4.0
5
5.2
4.4
V
V
BST
SHDN
IN
l
4.2
BSTUVLO
V
IN
V
IN
< 1.4V
≥ 1.4V
7
10
mA
mA
(BOOST ENABLED, VSW = 0V)
The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at
TA = 25°C. VIN = 1.5V, VOUT = 1.2V, VBST = 5V, CIN = CBST = 1μF, COUT = 10μF (all capacitors ceramic) unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
5.5
200
20
UNITS
V
l
l
l
l
l
l
V
Operating Voltage
(Note 2)
1.14
IN
I
I
Operating Current
I
= 100μA, V
= V , 1.2V ≤ V ≤ 5V
95
0.6
5
μA
μA
V
IN
INSHDN
OUT
SHDN
IN
IN
Shutdown Current
V
SHDN
V
SHDN
= 0V, V = 3.5V
IN
V
V
Boost Operating Voltage (Note 7)
Undervoltage Lockout
Boost Operating Current
Boost Shutdown Current
= V
4.5
4.0
5.5
4.4
275
5
BST
IN
4.25
175
1
V
BSTUVLO
BST
I
I
I
= 100μA, V
= V
μA
μA
OUT
SHDN
IN
V
SHDN
= 0V
BSTSHDN
(BOOST ENABLED or DISABLED)
The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at
TA = 25°C. VIN = 1.5V, VOUT = 1.2V, CIN = CBST = 1μF, COUT = 10μF (all capacitors ceramic) unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Regulation Voltage (Note 5)
1mA ≤ I
1mA ≤ I
≤ 1.5A, 1.14V ≤ V ≤ 3.5V, V
= 5V, V
= 5V, V
= 0.8V
= 0.8V
0.397
0.395
0.4
0.4
0.403
0.405
V
V
ADJ
OUT
OUT
IN
BST
BST
OUT
OUT
l
l
l
l
l
≤ 1.5A, 1.14V ≤ V ≤ 3.5V, V
IN
OUT
Programming Range
0.4
2.6
250
100
V
mV
nA
A
Dropout Voltage (Note 6)
ADJ Input Current
V
IN
= 1.5V, V
= 0.38, I = 1.5A
OUT
100
ADJ
I
I
I
V
ADJ
= 0.4V
–100
1.5
ADJ
OUT
LIM
Continuous Output Current
Output Current Current Limit
Output Voltage Noise
V = V
SHDN IN
3
A
e
n
f = 10Hz to 100kHz, I = 800mA
Boost Disabled
Boost Enabled
L
110
210
μV
μV
RMS
RMS
3026fc
3
LTC3026
ELECTRICAL CHARACTERISTICS
VIN = 1.5V, VOUT = 1.2V, CIN = CBST = 1μF, COUT = 10μF (all capacitors ceramic) unless otherwise noted.
(BOOST ENABLED or DISABLED)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
SYMBOL PARAMETER
CONDITIONS
1.14V ≤ V ≤ 3.5V
MIN
TYP
MAX
UNITS
l
l
V
SHDN Input High Voltage
1.0
1.2
V
V
IHSHDN
IN
3.5V ≤ V ≤ 5.5V
IN
l
l
V
SHDN Input Low Voltage
SHDN Input High Current
SHDN Input Low Current
PG Output Low Voltage
1.14V ≤ V ≤ 5.5V
0.4
1
V
μA
μA
V
ILSHDN
IHSHDN
ILSHDN
IN
I
I
SHDN = V
–1
–1
IN
SHDN = 0V
1
V
I
= 2mA
= 5.5V
0.1
0.4
1
OLPG
OHPG
PG
I
PG Output High Leakage Current
Output Threshold (Note 4)
V
0.01
μA
PG
PG
PG High to Low
PG Low to High
–12
–10
–9
–7
–6
–4
%
%
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime. This IC has overtemperature protection that is
intended to protect the device during momentary overload conditions.
Junction temperatures will exceed 125°C when overtemperature is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
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. When operating at maximum output current, the input voltage
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
Note 2: Minimum Operating Voltage required for regulation is:
output voltage will be equal to V – V
.
IN
DROPOUT
V
≥ V
+ V
IN
OUT(MIN) DROPOUT
Note 7: To maintain correct regulation
Note 3: When using BST to drive loads other than LTC3026s, the load
must be high impedance during start-up (i.e. prior to PG going high).
V
OUT
≤ V
– 2.4V
BST
Note 8: The LTC3026E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3026I is guaranteed
over the full –40°C to 125°C operating junction temperature range.
Note 4: PG threshold expressed as a percentage difference from the
“V Regulation Voltage” as given in the table.
ADJ
TYPICAL PERFORMANCE CHARACTERISTICS
IN Supply Current with Boost
Converter Enabled
BST Supply Current with Boost
Converter Disabled
IN Supply Current with Boost
Converter Disabled
1.50
1.25
1.00
0.75
0.50
0.25
0
200
150
100
50
200
150
100
50
V
= 5V
V
BST
= 5V
BST
–40°C
25°C
–40°C
25°C
–40°C
25°C
85°C
85°C
125°C
85°C
125°C
0
0
1.0
1.5
2.0
2.5
(V)
3.0
3.5
2.0 2.5
2.0 2.5
3.0 3.5 4.0 4.5 5.0 5.5
1.0 1.5
3.0 3.5 4.0 4.5 5.0 5.5
(V)
1.0 1.5
V
V
V
(V)
IN
IN
IN
3026 G01
3026 G02
3026 G03
3026fc
4
LTC3026
TYPICAL PERFORMANCE CHARACTERISTICS
ADJ Voltage vs Temperature
IN Shutdown Current
BST Voltage vs Temperature
5.050
5.025
5.000
4.975
4.950
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
404
403
402
401
400
399
398
397
396
V
= 1.5V
IN
1mA
1.5A
3.5V
1.2V
V
V
V
= 5V
BST
IN
OUT
= 1.5V
2.5V
=1.2V
0
25
50
100 125
–50 –25
75
0
25
50
100 125
–50 –25
75
0
25
50
100 125
–50 –25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3026 G06
3026 G04
3026 G05
Dropout Voltage vs Input Voltage
Ripple Rejection
Ripple Rejection
200
180
160
140
120
100
80
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
V
OUT
= 0.38V
FB
10kHz
1MHz
I
=1.5A
100kHz
60
V
V
V
I
= 5V
= 1.5V
=1.2V
= 800mA
= 10μF
BST
IN
OUT
OUT
–40°C
25°C
85°C
125°C
V
V
I
= 5V
BST
OUT
OUT
40
=1.2V
= 800mA
= 10μF
20
C
C
OUT
OUT
0
1.4
1.6 1.8 2.0
(V)
2.4 2.6
1.2
2.2
2.0
(V)
2.4
2.6
1000
10000
1000000 1E+07
100000
1.2 1.4
1.6 1.8
V
2.2
100
V
FREQUENCY (Hz)
IN
IN
3026 G07
3026 G08
3026 G09
Shutdown Threshold
Output Current Limit
BST to OUT Headroom Voltage
2.22
2.20
2.18
2.16
2.14
2.12
2.10
2.08
2.06
2.04
2.02
1200
900
600
300
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
V
T
= 0V
OUT
A
= 25°C
RISE
RISE
FALL
FALL
RISE
FALL
CURRENT LIMIT
–40°C
25°C
125°C
THERMAL LIMIT
–50
0
25
50
75 100 125
–25
1.5
2.0
3.0
2.5
1
2
3
4
5
6
1.0
3.5
TEMPERATURE (°C)
V
(V)
V
(V)
IN
IN
3026 G12
3026 G10
3026 G11
3026fc
5
LTC3026
TYPICAL PERFORMANCE CHARACTERISTICS
Delay from Enable to PG with
Boost Disabled
Delay from Enable to PG with
Boost Enabled
Output Load Transient Response
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.5A
2mA
400
375
350
325
300
275
250
V
= 0.8V
OUT
OUT
I
OUT
R
= 8Ω
–40°C
25°C
85°C
OUT
AC 20mV/DIV
V
= 0.8V
OUT
OUT
R
= 8Ω
–40°C
25°C
85°C
3026 G15
1.0
1.5
2.0
V
2.5
(V)
3.0
3.5
50μs/DIV
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
(V)
V
C
V
V
= 1.5V
= 10μF
OUT
OUT
IN
V
IN
IN
3026 G14
3026 G13
= 1.7V
= 5V
BST
BST Ripple and Feedthrough
to OUT
IN Supply Transient Response
BST/OUT Start-Up
HI
LO
5V
SHDN
2V
V
IN
V
1.5V
BST
AC 20mV/DIV
BST
1V
1.5V
V
OUT
AC
V
OUT
AC 5mV/DIV
10mV/DIV
OUT
0V
3026 G17
3026 G16
3026 G18
200μs/DIV
10μs/DIV
20μs/DIV
T
= 25°C
A
V
= 1.2V
= 800mA
= 10μF
= 5V
V
V
OUT
C
= 1.2V
OUT
OUT
OUT
OUT
BST
R
= 1Ω
OUT
I
= 1.5V
IN
V
= 1.7V
IN
C
V
I
= 1A
= 10μF
OUT
T
A
= 25°C
L
T
= 10μH
SW
A
= 25°C
PIN FUNCTIONS
IN (Pins 1, 2): Input Supply Voltage. Output load current
is supplied directly from IN. The IN pin should be locally
bypassedtogroundiftheLTC3026ismorethanafewinches
away from another source of bulk capacitance. In general,
the output impedance of a battery rises with frequency, so
it is usually advisable to include an input bypass capacitor
when supplying IN from a battery. A capacitor in the range
of 0.1μF to 4.7μF is usually sufficient.
GND (Pins 3, 11): Ground and Heat Sink. Connect to
PCB ground plane or large pad for optimum thermal
performance.
SW(Pin4):BoostSwitchingPin.Thisistheboostconverter
switching pin. A 4.7μH to 40μH inductor able to handle a
peak current of 150mA is connected from this pin to V .
IN
The boost converter can be disabled by shorting this pin
to GND. This allows the use of an external boosted supply
from a second LTC3026 or other source.
3026fc
6
LTC3026
PIN FUNCTIONS
BST (Pin 5): Boost Output Voltage Pin. With boost con-
PG (Pin 7): Power Good Pin. When PG is high impedance
OUT is in regulation, and low impedance when OUT is in
shutdown or out of regulation.
verter enabled bypass the BST pin with a ≥4.7μF low ESR
ceramic capacitor to GND (C ). BST does not load V
BST
IN
when in shutdown, but is diode connected to IN through
ADJ(Pin8):OutputAdjustPin.Thisistheinputtotheerror
amplifier. It has a typical bias current of 0.1nA flowing into
the pin. The ADJ pin reference voltage is 0.4V referenced
to ground. The output voltage range is 0.4V to 2.6V and is
typically set by connecting ADJ to a resistor divider from
OUT to GND. See Figure 2.
the external inductor, thus, will not go to ground with V
IN
present. Users should not present any loads to the BST
pin (with boost enabled) until PG signals that regulation
has been achieved. When providing an external BST volt-
age (i.e. boost converter disabled) a 1μF low ESR ceramic
capacitor can be used.
OUT(Pins9,10):RegulatedOutputVoltage.TheOUTpins
supply power to the load. A minimum output capacitance
of5μFisrequiredtoensurestability. Largeroutputcapaci-
tors may be required for applications with large transient
loads to limit peak voltage transients. See the Applica-
tions Information section for more information on output
capacitance.
SHDN (Pin 6): Shutdown Input Pin, Active Low. This pin
is used to put the LTC3026 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 (such
as IN) if not used.
BLOCK DIAGRAM
BOOST
CONVERTER
SW
4
6
5 BST
–
+
SHDN
SWITCHING
LOGIC
EN
IN
1,2
SHDN
REFERENCE
0.4V
+
–
UVLO
OUT
9,10
V
OFF
–
+
PG
–
7
–
+
+
0.372V
8
ADJ
OVERSHOOT DETECT
GND
3,11
3026 BD
3026fc
7
LTC3026
OPERATION
TheLTC3026isaVLDO(verylowdropout)linearregulator
which operates from input voltages as low as 1.14V. The
LDO uses an internal NMOS transistor as the pass device
in a source-follower configuration. The BST pin provides
thehighersupplynecessaryfortheLDOcircuitrywhilethe
output current comes directly from the IN input for high
efficiency regulation. The BST pin can either be supplied
off-chip by an external 5V source or it can be generated
through the internal boost converter of the LTC3026.
Ifanexternal5Vsupplyisused,theinternalboostconverter
can be disabled by shorting SW to GND except in cases
where the external 5V supply is current limited. If the
external 5V supply is current limited to less than 200mA
then the internal boost converter should be disabled by
floating the SW pin.
A single LTC3026 boost converter can be used to drive
multiple bootstrapped LTC3026s with the internal boost
converters disabled. Thus a single inductor can be used
to power two (or possibly more) functioning LTC3026s.
In cases where all LTC3026s have the same input supply
(IN) the internal boost converters of the bootstrapped
LTC3026s are disabled by shorting SW to GND. If the
LTC3026s are not all connected to the same input supply
then the internal boost converters of the bootstrapped
LTC3026s are disabled by floating the SW pin.
Boost Converter Operation
For applications where an external 5V supply is not avail-
able, the LTC3026 contains an internal boost converter to
produce the necessary 5V supply for the LDO. The boost
converter utilizes Burst Mode® operation to achieve high
efficiency for the relatively low current levels needed for
the LDO circuitry. The boost converter requires only a
small chip inductor between the IN and SW pins and a
small 4.7μF capacitor at BST.
Care must be taken not to short the BST pin to GND, since
the body diode of the internal PMOS transistor connects
the BST and SW pins. Shorting BST to GND with an induc-
tor connected between IN and SW can ramp the inductor
current to destructive levels, potentially destroying the
inductor and/or the part.
The operation of the boost converter is described as fol-
lows.Duringthefirsthalfoftheswitchingcycle,aninternal
NMOS switch between SW and GND turns on, ramping
the inductor current. A peak comparator senses when the
inductorcurrentreaches100mA,atwhichpointtheNMOS
is turned off and an internal PMOS between SW and BST
turns on, transferring the inductor current to the BST pin.
The PMOS switch continues to deliver power to BST until
the inductor current approaches zero, at which point the
PMOS turns off and the NMOS turns back on, repeating
the switching cycle.
LDO Operation
An undervoltage lockout comparator (UVLO) senses the
BST pin voltage to ensure that the bias supply for the LDO
is greater than 4.2V before enabling the LDO. If BST is
below 4.2V, the UVLO shuts down the LDO, and OUT is
pulled to GND through the external divider.
The LDO provides a high accuracy output capable of
supplying 1.5A of output current with a typical dropout
voltage of only 100mV. A single ceramic capacitor as
small as 10μF is all that is required for output bypassing.
A low reference voltage allows the LTC3026 output to be
programmed to much lower voltages than available in
common LDOs (range of 0.4V to 2.6V).
Aburstcomparatorwithhysteresismonitorsthevoltageon
the BST pin. When BST is above the upper threshold of the
comparator,noswitchingoccurs.WhenBSTfallsbelowthe
comparator’s lower threshold, switching commences and
the BST pin gets charged. The upper and lower thresholds
of the burst comparator are set to maintain a 5V supply at
BST with approximately 40mV to 50mV of ripple.
The devices also include current limit and thermal over-
load protection, and will survive an output short-circuit
indefinitely. 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 LTC3026 has an option to disable the internal boost
converter. With the boost converter disabled, the LTC3026
becomes a bootstrapped device and the BST pin must be
driven by an external 5V supply, or driven by the BST pin
of a second LTC3026 with the boost converter enabled.
Burst Mode is a registered trademark of Linear Technology Corporation.
see Figure 1.
3026fc
8
LTC3026
OPERATION
1.5A
R2
R1
¥
´
V
ꢀ 0.4V 1ꢁ
I
V
OUT
OUT
¦
§
µ
¶
OUT
0mA
LTC3026
R2
R1
C
ADJ
OUT
OUT
AC 20mV/DIV
GND
3026 F03
Figure 3. Programming the LTC3026
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 3. Note that in shutdown the
output is turned off and the divider current will be zero
3026 F01
V
C
V
V
= 1.5V
100μs/DIV
OUT
OUT
IN
B
= 10μF
= 1.7V
= 5V
Figure 1. Output Load Step Response
once C
is discharged.
OUT
The LTC3026 operates at a relatively high gain of
270μV/A refered to the ADJ input. Thus, a load current
change of 1mA to 1.5A produces a 400μV drop at the ADJ
input. To calculate the change in the output, simply mul-
tiply by the gain of the feedback network (i.e. 1 + R2/R1).
For example, to program the output for 1.2V choose
R2/R1 = 2. In this example an output current change of
1mA to 1.5A produces –400μV • (1 + 2) = 1.2mV drop at
the output.
HI
SHDN
LO
1.5V
OUT
0V
1.5V
0V
PG
Power Good Operation
3026 F02
T
= 25°C
100μs/DIV
A
R
V
= 1Ω
OUT
= 1.7V
IN
= 5V
The LTC3026 includes an open-drain power good (PG)
output pin with hysteresis. If the chip is in shutdown or
V
B
Figure 2. Soft-Start with Boost Disable
under UVLO conditions (V
< 4.25V), PG is low im-
BST
pedance to ground. PG becomes high impedance when
rises to 93% of its regulation voltage. PG stays high
The LTC3026 also includes a soft-start feature to prevent
V
OUT
excessive current flow at V during start-up. When the
impedanceuntilV
fallsbackdownto91%ofitsregula-
IN
OUT
LDOisenabled, thesoft-startcircuitrygraduallyincreases
the LDO reference voltage from 0V to 0.4V over a period
of approximately 200μs, see Figure 2.
tion value. A pull-up resistor can be inserted between PG
and a positive logic supply (such as IN, OUT, BST, etc.)
to signal a valid power good condition. V should be the
IN
minimum operating voltage (1.14V) or greater for PG to
function correctly.
Adjustable Output Voltage
The output voltage is set by the ratio of two external resis-
tors as shown in Figure 3. 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
goodtransientresponse,stabilityandaccuracythecurrent
in R1 should be at least 80μA, thus, the value of R1 should
be no greater than 5k. The current in R2 is the current in
Output Capacitance and Transient Response
The LTC3026 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 ca-
pacitors. An output capacitor of 10μF or greater with an
ESR of 0.05Ω or less is recommended to ensure stability.
3026fc
9
LTC3026
OPERATION
The LTC3026 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 LTC3026
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.
temperature and applied voltage. The most common di-
electrics 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 tem-
perature coefficients as shown in Figures 4 and 5. When
used with a 2V regulator, a 10μF Y5V capacitor can exhibit
an effective value as low as 1μF to 2μF 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, while the X5R is less expensive and
is available in higher values.
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
A minimum capacitance of 5μF must be maintained at all
times on the LTC3026 LDO output.
20
BOTH CAPACITORS ARE 10μF,
6.3V, 0805 CASE SIZE
0
–20
X5R
–40
–60
Y5V
–80
–100
0
1
2
3
4
5
6
DC BIAS VOLTAGE (V)
3026 F04
Figure 4. Ceramic Capacitor DC Bias Characteristics
20
X5R
0
–20
Y5V
–40
–60
–80
BOTH CAPACITORS ARE 10μF,
6.3V, 0805 CASE SIZE
–100
50
–50
–25
0
25
75
TEMPERATURE (°C)
3026 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
3026fc
10
LTC3026
OPERATION
Boost Converter Component Selection
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 gener-
ated by power devices.
A 10μH chip inductor with a peak saturation current (I
)
SAT
ofatleast150mAisrecommendedforusewiththeinternal
boost converter. The inductor value can range between
4.7μH to 40μH, but values less than 10μH result in higher
switchingfrequency,increasedswitchinglosses,andlower
max output current available at the BST pin. See Table 1
for a list of component suppliers.
A junction-to-ambient thermal coefficient of 40°C/W is
achieved by connecting the exposed pad of the MSOP
or DFN package directly to a ground plane of about
2
2500mm .
Table 1. Inductor Vendor Information
SUPPLIER
Coilcraft
Murata
PART NUMBER
0603PS-103KB
WEBSITE
Calculating Junction Temperature
www.coilcraft.com
www.murata.com
www.t-yuden.com
www.TDK.com
Example: Given an output voltage of 1.2V, an input voltage
of 1.8V 4%, an output current range of 0mA to 1A and
a maximum ambient temperature of 50°C, what will the
maximum junction temperature be?
LQH2MCN100K02
LB2016T100M
Taiyo Yuden
TDK
NLC252018T-100K
It is also recommended that the BST pin be bypassed to
ground with a 4.7μF or greater ceramic capacitor. Larger
values of capacitance will not reduce the size of the BST
ripplemuch,butwilldecreasetheripplefrequencypropor-
tionally. The BST pin should maintain 1μF of capacitance
at all times to ensure correct operation (See the “Output
Capacitance and Transient Response” section about
capacitor selection). High ESR tantalum and electrolytic
capacitors may be used, but a low ESR ceramic must be
used in parallel for correct operation.
The power dissipated by the device will be approximately:
I
(V
– V
)
OUT(MAX) IN(MAX)
OUT
where:
I
= 1A
OUT(MAX)
V
= 1.87V
IN(MAX)
so:
P = 1A(1.87V – 1.2V) = 0.67W
Even under worst-case conditions LTC3026’s BST pin
powerdissipationisonlyabout1mW, thuscanbeignored.
The junction to ambient thermal resistance will be on the
order of 40°C/W. The junction temperature rise above
ambient will be approximately equal to:
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C).
The majority of the power dissipated in the device will be
the output current multiplied by the input/output voltage
0.67W(40°C/W) = 26.8°C
differential: (I )(V – V ). Note that the BST current
OUT
IN
OUT
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
is less than 200μA even under heavy loads, so its power
consumption can be ignored for thermal calculations.
The LTC3026 has internal thermal limiting designed to
protectthedeviceduringmomentaryoverloadconditions.
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.
T = 26.8°C + 50°C = 76.8°C
A
Short-Circuit/Thermal Protection
The LTC3026 has built-in output short-circuit current
limiting as well as overtemperature protection. During
short-circuit conditions, internal circuitry automatically
3026fc
11
LTC3026
OPERATION
limits the output current to approximately 3A. At higher
temperatures, or in cases where internal power dissipa-
tion cause excessive self heating on-chip, the thermal
shutdowncircuitrywillshutdowntheboostconverterand
LDOwhenthejunctiontemperatureexceedsapproximately
150°C. It will reenable the converter and LDO once the
junction temperature drops back to approximately 140°C.
The LTC3026 will cycle in and out of thermal shutdown
without latchup or damage until the overstress condition
Layout Considerations
Connection from BST and OUT pins to their respec-
tive 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.
is removed. Long term overstress (T > 125°C) should
J
With the boost converter enabled, the SW pin will be
switching between ground and 5V whenever the BST pin
needstoberecharged. ThetransitionedgeratesoftheSW
pin can be quite fast (~10ns). Thus care must be taken to
make sure the SW node does not couple capacitively to
other nodes (especially the ADJ pin). Additionally, stray
capacitancetothisnodereducestheefficiencyandamount
of current available from the boost converter. For these
reasons it is recommended that the SW pin be connected
to the switching inductor with as short a trace as possible.
If the user has any sensitive nodes near the SW node, a
ground shield may be placed between the two nodes to
reduce coupling.
be avoided as it can degrade the performance or shorten
the life of the part.
Reverse Input Current Protection
The LTC3026 features reverse input current protection to
limit current draw from any supplementary power source
at the output. Figure 6 shows the reverse output current
limit for constant input and output voltages cases. Note:
Positive input current represents current flowing into the
V pin of LTC3026.
IN
With V
held at or below the output regulation voltage
OUT
andV varied,INcurrentflowwillfollowFigure6’scurves.
IN
I
reverse current ramps up to about 16μA as the V
IN
IN
BecausetheADJpinisrelativelyhighimpedance(depend-
ing on the resistor divider used), stray capacitance at this
pin should be minimized (<10pF) to prevent phase shift
in the error amplifier loop. Additionally 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.
approaches V . Reverse input current will spike up as
OUT
V approaches within about 30mV of V
as the reverse
IN
OUT
current protection circuitry is disabled and normal opera-
tion resumes. As V transitions above V the reverse
IN
OUT
current transitions into short-circuit current as long as
V
is held below the regulation voltage.
OUT
30
IN CURRENT
LIMIT ABOVE 1.45V
20
10
C
C
OUT
IN
1
2
3
4
5
IN
OUT 10
0
IN
9
8
7
6
OUT
ADJ
R2
R1
GND
SW
BST
–10
–20
–30
PG
SHDN
C
BST
3026 F07
0
0.9
INPUT VOLTAGE (V)
1.5
0.3
0.6
1.2
1.8
VIA CONNECTION TO GND PLANE
3026 F06
Figure 6. Input Current vs Input Voltage
Figure 7. Suggested Layout
3026fc
12
LTC3026
TYPICAL APPLICATIONS
Using 1 Boost with Multiple Regulators
V
= 2.5V
IN
TO ADDITIONAL
REGULATORS
10μH
BST
OUT
BST
OUT
SW
IN
SW*
4.7μF
1μF
LTC3026
LTC3026
V
V
OUT2
1.5V, 1.5A
OUT1
IN
1.8V, 1.5A
14k
11k
C
C
OUT1
OUT2
ADJ
PG
ADJ
PG
SHDN
SHDN
10μF
10μF
100k
100k
4.02k
4.02k
4.7μF
1μF
PG1
PG2
GND
GND
LTC3026 WITH BOOST ENABLED FANOUT:
3-LTC3026 FOR V <1.4V
BOOT STRAPPED LTC3026
(BOOST DISABLED)
IN
3026 TA02
5-LTC3026 FOR V >1.4V
IN
* THE SW PIN OF BOOTSTRAPPED LTC3026 SHOULD BE FLOATED (DISCONNECTED FROM GND) IN CASES WHERE THE BOOTSTRAPPED
LTC3026 DOES NOT SHARE THE SAME INPUT SUPPLY (IN) AS THE BOOSTING LTC3026.
2.5V Output from 3.3V Supply with External 5V Bias
V
= 5V
BIAS
BST
OUT
SW*
IN
1μF
LTC3026
V
OUT
V
= 3.3V
IN
2.5V, 1.5A
21k
C
OUT
ADJ
PG
SHDN
10μF
100k
4.02k
1μF
PG
GND
3026 TA03
* THE SW PIN SHOULD BE FLOATED (DISCONNECTED FROM GND)
IF THE EXTERNAL 5V BIAS SUPPLY IS CURRENT LIMITED TO LESS
THAN 200mA.
3026fc
13
LTC3026
PACKAGE DESCRIPTION
MSE Package
10-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1664 Rev C)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 p 0.102
(.081 p .004)
1.83 p 0.102
(.072 p .004)
2.794 p 0.102
(.110 p .004)
0.889 p 0.127
(.035 p .005)
1
0.29
REF
0.05 REF
5.23
(.206)
MIN
2.083 p 0.102 3.20 – 3.45
(.082 p .004) (.126 – .136)
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
DETAIL “B”
10
0.50
(.0197)
BSC
0.305 p 0.038
(.0120 p .0015)
TYP
3.00 p 0.102
(.118 p .004)
(NOTE 3)
0.497 p 0.076
(.0196 p .003)
10 9
8
7 6
RECOMMENDED SOLDER PAD LAYOUT
REF
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
DETAIL “A”
0.254
(.010)
0o – 6o TYP
1
2
3
4 5
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 p 0.0508
(.004 p .002)
0.50
(.0197)
BSC
MSOP (MSE) 0908 REV C
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
3026fc
14
LTC3026
PACKAGE DESCRIPTION
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1669 Rev B)
0.70 p0.05
3.55 p0.05
2.15 p0.05 (2 SIDES)
1.65 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50
BSC
2.38 p0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.125
0.40 p 0.10
TYP
6
10
3.00 p0.10
(4 SIDES)
1.65 p 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
(DD) DFN REV B 0309
5
1
0.25 p 0.05
0.50 BSC
0.75 p0.05
0.200 REF
2.38 p0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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
3026fc
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC3026
TYPICAL APPLICATION
Efficient, Low Noise 1.5V Output from 1.8V DC/DC Buck Converter
(LTC3026 Boost Converter Disabled)
4.5V b V b 5.5V
IN
33pF
200pF
30k
1
2
3
4
5
10
I
SW
–
TH
R
SENSE
0.04Ω
0.1μF
LTC1773
9
8
7
6
RUN/SS SENSE
1μF
V
1.8V
2A
BUCK
SYNC/FCB
V
IN
SW
IN
BST
OUT
ADJ
PG
L1
LTC3026
2.5μH
V
1.5V
1.5A
V
TG
BG
OUT
FB
C
IN
11k
GND
47μF
10V
C
OUT
SHDN
10μF
1μF
4.02k
Si9942DY
100k
C
47μF
10V
BUCK
PG
GND
100k
1%
80.6k
1%
3026 TA04
C
, C : TAIYO YUDEN LMK550BJ476MM
IN BUCK
L1: CDRH5D28
R
: IRC LR1206-01-R040-F
SENSE
RELATED PARTS
PART NUMBER
LT1761
DESCRIPTION
COMMENTS
100mA, Low Noise LDO in ThinSOT
150mA, Low Noise LDO
300mV Dropout Voltage, Low Noise: 20μV
300mV Dropout Voltage, Low Noise: 20μV
300mV Dropout Voltage, Low Noise: 20μV
, V = 1.8V to 20V, ThinSOT Package
RMS IN
LT1762
, V = 1.8V to 20V, MS8 Package
RMS IN
LT1763
500mA, Low Noise LDO
, V = 1.8V to 20V, SO-8 Package
RMS IN
LT1764A
3A, Fast Transient Response, Low Noise LDO 340mV Dropout Voltage, Low Noise: 40μV
, V = 2.7V to 20V,
RMS IN
TO-220 and DD Packages
LT1844
150mA, Very Low Dropout LDO
300mA, Low Noise LDO
80mV Dropout Voltage, Low Noise <30μV
, V = 1.6V to 6.5V,
RMS IN
Stable with 1μF Output Capacitors, ThinSOT Package
LT1962
270mV Dropout Voltage, Low Noise 20μV , V = 1.8V to 20V, MS8 Package
RMS IN
LT1963A
1.5A Low Noise, Fast Transient Response LDO 340mV Dropout Voltage, Low Noise: 40μV
, V = 2.5V to 20V,
RMS IN
TO-220, DD, SOT-223 and SO-8 Packages
LT1964
LTC3025
LT3150
200mA, Low Noise, Negative LDO
340mV Dropout Voltage, Low Noise 30μV
, V = –1.8V to –20V,
RMS IN
ThinSOT Package
300mA Micropower VLDO Linear Regulator
45mV Dropout Voltage, Low Noise 80μV
, V = 0.9V to 5.5V,
RMS IN
Low I : 54μA, 2mm × 2mm 6-Lead DFN Package
Q
Fast Transient Response, VLDO Regulator
Controller
0.035mV Dropout Voltage via External FET, V : 1.3V to 10V
IN
3026fc
LT 0609 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2005
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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LTC3026EMSE#PBF
LTC3026 - 1.5A Low Input Voltage VLDO Linear Regulator; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C
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