概述
数据手册
替代型号LTC3026EMSE 概述
1.5A Low Input Voltage VLDO Linear Regulator 1.5A低输入电压VLDO线性稳压器 稳压芯片
LTC3026EMSE 数据手册
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PDF下载LTC3026
1.5A Low Input Voltage
VLDO Linear Regulator
U
FEATURES
DESCRIPTIO
The LTC®3026 is a very low dropout (VLDOTM) linear
regulatorthatcanoperateatinputvoltagesdownto1.14V.
The device is capable of supplying 1.5A of output current
with a typical dropout voltage of only 100mV. To allow
operation at low input voltages the LTC3026 includes a
boostconverterthatprovidesthenecessaryheadroomfor
the internal LDO circuitry.
■
Input Voltage Range:
1.14V to 3.5V (with Boost Enabled)
1.14V to 5.5V (with External 5V Boost)
■
Low Dropout Voltage: 100mV at IOUT = 1.5A
■
Adjustable Output Range: 0.4V to 2.6V
Output Current: Up to 1.5A
■
■
Excellent Supply Rejection Even Near Dropout
■
Shutdown Disconnects Load from VIN and VBST
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: IIN = 950µA at VIN = 1.5V
■
Low Shutdown Current:
IIN < 1µA (Typ), IBST = 0.1µA (Typ)
■
Stable with 10µF or Greater Ceramic Capacitors
■
Short-Circuit, Reverse Current Protected
■
Overtemperature Protected
■
Available in 10-Lead MSOP and 10-Lead
(3mm × 3mm) DUFN 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.
APPLICATIO S
■
High Efficiency Linear Regulator
■
Post Regulator for Switching Supplies
■
Microprocessor Supply
, 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.
Patent Pending
U
TYPICAL APPLICATIO
1.2V Output Voltage from 1.5V Input Supply
Dropout Voltage vs Output Current
L1
10µH
150
SW
BST
5V BOOST
CONVERTER
4.7µF
IN
100
V
= 1.5V
IN
1.2V
1.5V
2.0V
2.6V
+
–
0.4V
4.7µF
V
= 1.2V,
OUT
ADJ
OUT
1.5A
50
0
8.06k
4.02k
C
OUT
10µF
OFF ON
SHDN
GND
LTC3026
100k
1.0
1.5
PG
0
0.5
3026 TA01a
I
(A)
OUT
3026 TA01b
L1: MURATA LQH2MCN100K02
3026f
1
LTC3026
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
Operating Junction Temperature
VBST to GND ................................................ –0.3V to 6V
VIN to GND................................................... –0.3V to 6V
SHDN, and ADJ to GND ................ –0.3V to (VIN + 0.3V)
Output Short-Circuit Duration.......................... Indefinite
Range ............................................... –40°C to 125°C
Storage Temperature Range ................. –65°C to 125°C
Lead Temperature (MSE, Soldering, 10 sec) ........ 300°C
U
W
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
ORDER PART
TOP VIEW
NUMBER
NUMBER
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
LTC3026EDD
LTC3026EMSE
9
8
7
6
OUT
ADJ
PG
GND
SW
BST
11
11
SHDN
SHDN
DD PART
MARKING
MSE PART
MARKING
MSE PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 40°C/W
EXPOSED PAD IS GND (PIN 11)
MUST BE SOLDERED TO PCB
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 40°C/W
LBHW
LTBJB
EXPOSED PAD IS GND (PIN 11)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
(BOOST ENABLED, LSW = 10µH)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating 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
V
Operating Voltage
Operating Current
(Note 2)
●
1.14
3.5
V
IN
I
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
IN
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
I
Shutdown Current
V
= 0V, V = 3.5V
●
●
0.6
10
20
40
µA
INSHDN
SHDN
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
4.2
BSTUVLO
V
V
< 1.4V
≥ 1.4V
7
10
mA
mA
IN
IN
3026f
2
LTC3026
(BOOST DISABLED, VSW = 0V)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating 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
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
V
= 0V, V = 3.5V
IN
SHDN
SHDN
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
= 0V
SHDN
BSTSHDN
(BOOST ENABLED or DISABLED)
The ● denotes the specifications which apply over the full operating 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
≤ 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
V
V
= 1.5V, V
= 0.38, I = 1.5A
OUT
100
IN
ADJ
I
I
I
= 0.4V
–100
1.5
ADJ
OUT
LIM
ADJ
SHDN
Continuous Output Current
Output Current Current Limit
Output Voltage Noise
= V
IN
3
A
e
n
f = 10Hz to 100kHz, I = 800mA
L
Boost Disabled
Boost Enabled
110
210
µV
µV
RMS
RMS
V
V
SHDN Input High Voltage
1.14V ≤ V ≤ 3.5V
●
●
1.0
1.2
V
V
IHSHDN
IN
3.5V ≤ V ≤ 5.5V
IN
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
= 2mA
1
V
I
●
0.1
0.4
1
OLPG
OHPG
PG
I
PG Output High Leakage Current V = 5.5V
0.01
µA
PG
PG
Output Threshold (Note 4)
PG High to Low
PG Low to High
–12
–10
–9
–7
–6
–4
%
%
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired. 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 2: Minimum Operating Voltage required for regulation is:
Note 6: Dropout voltage is minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
V
≥ V
+ V
IN
OUT(MIN)
DROPOUT
output voltage will be equal to V – V
.
IN
DROPOUT
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).
Note 7: To maintain correct regulation
Note 4: PG threshold expressed as a percentage difference from the “V
V
≤ V
– 2.4V
ADJ
OUT
BST
Regulation Voltage” as given in the table.
3026f
3
LTC3026
U W
TYPICAL PERFOR A CE CHARACTERISTICS
IN Supply Current with Boost
Converter Disabled
IN Supply Current with Boost
Converter Enabled
BST 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
= 5V
BST
–40°C
25°C
BST
–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
1.0 1.5
1.0 1.5
3.0 3.5 4.0 4.5 5.0 5.5
(V)
3.0 3.5 4.0 4.5 5.0 5.5
(V)
V
V
V
IN
IN
IN
3026 G01
3026 G02
3026 G03
BST Voltage vs Temperature
ADJ Voltage vs Temperature
IN Shutdown Current
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
5.050
5.025
5.000
4.975
4.950
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
0
25
50
100 125
0
25
50
100 125
–50 –25
75
–50 –25
75
–50 –25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3026 G05
3026 G04
3026 G06
Ripple Rejection
Ripple Rejection
Dropout Voltage vs Input Voltage
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
C
OUT
40
=1.2V
= 800mA
= 10µF
20
C
OUT
0
1.4
1.6 1.8 2.0
(V)
2.4 2.6
2.0
(V)
2.4 2.6
1000
10000
1000000 1E+07
100000
1.2
2.2
1.2
1.8
V
2.2
100
1.4
1.6
V
FREQUENCY (Hz)
IN
IN
3026 G07
3026 G08
3026 G09
3026f
4
LTC3026
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Shutdown Threshold
Output Current Limit
BST to OUT Headroom Voltage
1200
900
600
300
2.22
2.20
2.18
2.16
2.14
2.12
2.10
2.08
2.06
2.04
2.02
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
V
= 0V
OUT
A
T
= 25°C
RISE
RISE
FALL
FALL
RISE
FALL
CURRENT LIMIT
–40°C
THERMAL LIMIT
25°C
125°C
1
2
3
4
5
6
1.5
2.0
3.0
2.5
1.0
3.5
–50
0
25
50
75
125
–25
100
V
IN
(V)
TEMPERATURE (°C)
V
IN
(V)
3026 G10
3026 G11
3026 G12
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
–40°C
25°C
85°C
OUT
I
OUT
R
= 8Ω
OUT
AC 20mV/DIV
V
= 0.8V
OUT
–40°C
25°C
85°C
OUT
R
= 8Ω
V
C
V
V
= 1.5V
100µs/DIV
1.0
1.5
2.0
V
2.5
(V)
3.0
3.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
(V)
OUT
OUT
IN
= 10µF
V
IN
IN
= 1.7V
= 5V
3026 G14
3026 G15
3026 G13
BST
BST Ripple and Feedthrough
to OUT
IN Supply Transient Response
BST/OUT Startup
HI
LO
5V
SHDN
BST
2V
1.5V
V
IN
V
BST
AC 20mV/DIV
1V
1.5V
V
OUT
AC
V
OUT
AC 5mV/DIV
10mV/DIV
OUT
0V
T
R
V
= 25°C
= 1Ω
IN
200µs/DIV
V
V
I
= 1.2V
V
I
= 1.2V
= 800mA
= 10µF
= 5V
A
OUT
OUT
IN
OUT
C
10µs/DIV
20µs/DIV
OUT
OUT
= 1.5V
= 1.7V
= 1A
C
3026 G16
3026 G17
3026 G18
OUT
BST
= 10µF
V
T
OUT
L
T
= 10µH
= 25°C
SW
A
= 25°C
A
3026f
5
LTC3026
U
U
U
PI FU CTIO S
IN (Pins 1, 2): Input Supply Voltage. Output load current
is supplied directly from IN. The IN pin should be locally
bypassed to ground if the LTC3026 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 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 suffi-
cient.
been achieved. When providing an external BST voltage
(i.e. boost converter disabled) a 1µF low ESR ceramic
capacitor can be used.
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.
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.
GND (Pins 3, 11): Ground and Heat Sink. Connect to
PCB ground plane or large pad for optimum thermal
performance.
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.
SW (Pin 4): Boost Switching Pin. This is the boost
converter switching pin. A 4.7µH to 40µH inductor able to
handle a peak current of 150mA is connected from this pin
to VIN. 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.
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 Applications
Information section for more information on output
capacitance.
BST (Pin 5): Boost Output Voltage Pin. With boost con-
verter enabled bypass the BST pin with a ≥4.7µF low ESR
ceramic capacitor to GND (CBST). BST does not load VIN
when in shutdown, but is diode connected to IN through
the external inductor, thus, will not go to ground with VIN
present. UsersshouldnotpresentanyloadstotheBSTpin
(with boost enabled) until PG signals that regulation has
3026f
6
LTC3026
W
BLOCK DIAGRA
BOOST
CONVERTER
SW
4
6
5 BST
–
+
SHDN
SWITCHING
LOGIC
EN
IN
1,2
SHDN
0.4V
+
–
REFERENCE
UVLO
OUT
9,10
V
OFF
–
+
PG
–
7
–
+
+
0.372V
8
ADJ
OVERSHOOT DETECT
GND
3,11
3026 BD
3026f
7
LTC3026
U
OPERATIO
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.
converter disabled the user must provide an external 5V
supply to BST, or the BST pin can be tied to the boosted
supply of a second LTC3026 with the boost converter
enabled. Thus only one inductor is required for two (or
possibly more) functioning LTC3026s.
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
inductor connected between IN and SW can ramp the
inductor current to destructive levels, potentially destroy-
ing the inductor and/or the part.
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.
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 and an internal
4k resistor.
The operation of the boost converter is described as
follows. During the first half of the switching cycle, an
internal NMOS switch between SW and GND turns on,
ramping the inductor current. A peak comparator senses
when the inductor current reaches 100mA, at which point
the NMOS 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.
The LDO provides a high accuracy output capable of
supplying 1.5A of output current with a typical dropout
voltageofonly100mV.Asingleceramiccapacitorassmall
as 10µF is all that is required for output bypassing. A low
reference voltage allows the LTC3026 output to be pro-
grammed to much lower voltages than available in com-
mon LDOs (range of 0.4V to 2.6V).
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,
see Figure 1.
A burst comparator with hysteresis monitors the voltage
on the BST pin. When BST is above the upper threshold of
the comparator, no switching occurs. When BST falls
below the comparator’s lower threshold, switching com-
mences and the BST pin gets charged. The upper and
lower thresholds of the burst comparator are set to main-
tain a 5V supply at BST with approximately 40mV to 50mV
of ripple.
The LTC3026 also includes a soft-start feature to prevent
excessive current flow at VIN during start-up. When the
LDOisenabled, thesoft-startcircuitrygraduallyincreases
the LDO reference voltage from 0V to 0.4V over a period
of approximately 200µs, see Figure 2.
The LTC3026 has an option to disable the internal boost
converter by shorting the SW pin to GND. With the boost
Burst Mode is a registered trademark of Linear Technology Corporation.
3026f
8
LTC3026
U
OPERATIO
1.5A
R2
R1
I
OUT
V
= 0.4V (1 +
)
V
OUT
OUT
0mA
LTC3026
R2
R1
C
ADJ
OUT
OUT
AC 20mV/DIV
GND
3026 F02
Figure 3. Programming the LTC3026
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.
V
C
V
V
= 1.5V
200µs/DIV
OUT
OUT
IN
B
= 10µF
= 1.7V
= 5V
Figure 1. Output Load Step Response
HI
LO
SHDN
OUT
1.5V
Power Good Operation
0V
1.5V
0V
The LTC3026 includes an open-drain power good (PG)
output pin with hysteresis. If the chip is in shutdown or
under UVLO conditions (VBST < 4.25V), PG is low imped-
ance to ground. PG becomes high impedance when VOUT
rises to 93% of its regulation voltage. PG stays high
impedance until VOUT falls back down to 91% of its
regulation value. A pull-up resistor can be inserted be-
tween PG and a positive logic supply (such as IN, OUT,
BST, etc.) to signal a valid power good condition. VIN
should be the minimum operating voltage (1.14V) or
greater for PG to function correctly.
PG
T
= 25°C
100µs/DIV
A
R
= 1Ω
OUT
V
V
= 1.7V
IN
= 5V
B
Figure 2. Soft-Start with Boost Disable
Adjustable Output Voltage
The output voltage is set by the ratio of two external
resistors as shown in Figure 3. The device servos the
output to maintain the ADJ pin voltage at 0.4V (referenced
toground). Thus, thecurrentinR1isequalto0.4V/R1. For
good transient response, stability and accuracy the cur-
rent 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 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 once COUT is discharged.
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 capaci-
toraffectsstability,mostnotablywithsmallcapacitors.An
output capacitor of 10µF or greater with an ESR of 0.05Ω
or less is recommended to ensure stability. 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 cur-
rentchanges.Notethatbypasscapacitorsusedtodecouple
3026f
9
LTC3026
U
OPERATIO
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.
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.
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 di-
electrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances
A minimum capacitance of 5µF must be maintained at all
times on the LTC3026 LDO output.
20
0
BOTH CAPACITORS ARE 10µF,
6.3V, 0805 CASE SIZE
X5R
–20
–40
–60
–80
–100
Y5V
0
1
2
3
4
5
6
DC BIAS VOLTAGE (V)
3026 F03
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 F04
Figure 5. Ceramic Capacitor Temperature Characteristics
3026f
10
LTC3026
U
OPERATIO
Boost Converter Component Selection
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
A 10µH chip inductor with a peak saturation current (ISAT
)
ofatleast150mAisrecommendedforusewiththeinternal
boost converter. The inductor value can range between
4.7µH to 40µH, but values less than 10µH result in higher
switching frequency, increased switching losses, and
lower max output current available at the BST pin. See
Table 1 for a list of component suppliers.
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.
Table 1. Inductor Vendor Information
A junction-to-ambient thermal coefficient of 40°C/W is
achieved by connecting the exposed pad of the MSOP or
DFNpackagedirectlytoagroundplaneofabout2500mm2.
SUPPLIER
Coilcraft
Murata
PART NUMBER
0603PS-103KB
WEBSITE
www.coilcraft.com
www.murata.com
www.t-yuden.com
www.TDK.com
LQH2MCN100K02
LB2016T100M
Calculating Junction Temperature
Taiyo Yuden
TDK
Example:Givenanoutputvoltageof1.2V, aninputvoltage
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?
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
ripple much, but will decrease the ripple frequency pro-
portionally. The BST pin should maintain 1µF of capaci-
tance at all times to ensure correct operation (See “Output
Capacitance and Transient Response” section about ca-
pacitor 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:
IOUT(MAX)(VIN(MAX) – VOUT
)
where:
IOUT(MAX) = 1A
VIN(MAX) = 1.87V
so:
P = 1A(1.87V – 1.2V) = 0.67W
Thermal Considerations
Even under worst-case conditions LTC3026’s BST pin
power dissipation is only about 1mW, thus can be ig-
nored. 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:
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
differential: (IOUT)(VIN – VOUT). Note that the BST current
is less than 200µA even under heavy loads, so its power
consumption can be ignored for thermal calculations.
0.67W(40°C/W) = 26.8°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
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
TA = 26.8°C + 50°C = 76.8°C
3026f
11
LTC3026
U
OPERATIO
Short-Circuit/Thermal Protection
Reverse Input Current Protection
The LTC3026 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 3A. At higher
temperatures, or in cases where internal power dissipa-
tion cause excessive self heating on-chip, the thermal
shutdowncircuitrywillshutdowntheboostconverterand
LDO when the junction temperature exceeds approxi-
mately 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 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.
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
VIN pin of LTC3026.
With VOUT held at or below the output regulation voltage
and VIN varied, IN current flow will follow Figure 6’s
curves. IIN reverse current ramps up to about 16µA as the
VIN approaches VOUT. Reverse input current will spike up
as VIN approaches within about 30mV of VOUT as the
reversecurrentprotectioncircuitryisdisabledandnormal
operation resumes. As VIN transitions above VOUT the
reverse current transitions into short circuit current as
long as VOUT is held below the regulation voltage.
30
20
IN CURRENT
LIMIT ABOVE 1.45V
10
0
–10
–20
–30
0
0.9
INPUT VOLTAGE (V)
1.5
0.3
0.6
1.2
1.8
3026 F06
Figure 6. Input Current vs Input Voltage
3026f
12
LTC3026
U
OPERATIO
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.
Layout Considerations
Connection from BST 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.
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.
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
C
C
IN
OUT
1
2
3
4
5
IN
OUT 10
IN
9
8
7
6
OUT
ADJ
R2
R1
GND
SW
BST
PG
SHDN
C
BST
3026 F05
VIA CONNECTION TO GND PLANE
Figure 7. Suggested Layout
3026f
13
LTC3026
U
TYPICAL APPLICATIO S
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
OUT1
IN
1.8V, 1.5A
1.5V, 1.5A
C
OUT2
14k
11k
C
OUT1
10µF
ADJ
PG
ADJ
PG
SHDN
GND
SHDN
GND
10µF
100k
100k
4.02k
4.02k
4.7µF
1µF
PG1
PG2
LTC3026 WITH BOOST ENABLED FANOUT:
3-LTC3026 FOR V <1.4V
BOOT STRAPPED LTC3026
(BOOST DISABLED)
IN
3026 TA03
5-LTC3025 FOR VI >1.4V
N
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
GND
10µF
100k
4.02k
1µF
PG
3026 TA04
3026f
14
LTC3026
U
PACKAGE DESCRIPTIO
MSE Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1663)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 ± 0.102
2.794 ± 0.102
(.110 ± .004)
0.889 ± 0.127
(.035 ± .005)
(.081 ± .004)
1
DETAIL “A”
0.254
1.83 ± 0.102
(.072 ± .004)
(.010)
0° – 6° TYP
GAUGE PLANE
5.23
(.206)
MIN
2.083 ± 0.102 3.20 – 3.45
(.082 ± .004) (.126 – .136)
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
10
0.18
(.007)
0.50
(.0197)
BSC
0.305 ± 0.038
(.0120 ± .0015)
TYP
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.497 ± 0.076
(.0196 ± .003)
REF
10 9
8
7 6
RECOMMENDED SOLDER PAD LAYOUT
0.86
1.10
(.034)
REF
(.043)
MAX
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
NOTE:
4.90 ± 0.152
(.193 ± .006)
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
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.127 ± 0.076
(.005 ± .003)
MSOP (MSE) 0603
1
2
3
4 5
0.50
(.0197)
BSC
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
6
0.38 ± 0.10
10
0.675 ±0.05
3.50 ±0.05
1.65 ±0.05
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
2.15 ±0.05 (2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PACKAGE
OUTLINE
(DD10) DFN 1103
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
0.25 ± 0.05
0.50
BSC
2.38 ±0.10
(2 SIDES)
2.38 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
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
3026f
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LTC3026
U
TYPICAL APPLICATIO
Efficient, Low Noise 1.5V Output from 1.8V DC/DC Buck Converter
(LTC3026 Boost Converter Disabled)
4.5V ≤ V ≤ 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
C
OUT
SHDN
GND
10V
10µF
1µF
4.02k
Si9942DY
100k
C
BUCK
PG
100k
1%
80.6k
1%
47µF
10V
3026 TA02
C
, C
: TAIYO YUDEN LMK550BJ476MM
IN BUCK
L1: CDRH5D28
: IRC LR1206-01-R040-F
R
SENSE
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT1761
100mA, Low Noise LDO in ThinSOT
300mV Dropout Voltage, Low Noise: 20µV
ThinSOT Package
, V = 1.8V to 20V,
RMS IN
LT1762
150mA, Low Noise LDO
300mV Dropout Voltage, Low Noise: 20µV
MS8 Package
, V = 1.8V to 20V,
RMS IN
LT1763
500mA, Low Noise LDO
300mV Dropout Voltage, Low Noise: 20µV
, V = 1.8V to 20V, SO-8 Package
RMS IN
LT1764A
3A, Fast Transient Response, Low Noise LDO
340mV Dropout Voltage, Low Noise: 40µV
TO-220 and DD Packages
, V = 2.7V to 20V,
RMS IN
LTC1844
LT1962
LT1963A
LT1964
LTC3025
LT3150
150mA, Very Low Dropout LDO
80mV Dropout Voltage, Low Noise <30µV
Stable with 1µF Output Capacitors, ThinSOT Package
, V = 1.6V to 6.5V,
RMS IN
300mA, Low Noise LDO
270mV Dropout Voltage, Low Noise: 20µV
MS8 Package
, V = 1.8V to 20V,
RMS IN
1.5A Low Noise, Fast Transient Response LDO
200mA, Low Noise, Negative LDO
340mV Dropout Voltage, Low Noise: 40µV
SOT-223 and SO-8 Packages
, V = 2.5V to 20V, TO-220, DD,
RMS IN
340mV Dropout Voltage, Low Noise 30µV
ThinSOT Package
, V = –1.8V to –20V,
RMS IN
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
3026f
LT/TP 0405 500 • 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
LTC3026EMSE 替代型号
| 型号 | 制造商 | 描述 | 替代类型 | 文档 |
| LTC3026EMSE#TRPBF | Linear | 暂无描述 | 完全替代 |
|
LTC3026EMSE 相关器件
| 型号 | 制造商 | 描述 | 价格 | 文档 |
| LTC3026EMSE#PBF | Linear | LTC3026 - 1.5A Low Input Voltage VLDO Linear Regulator; Package: MSOP; Pins: 10; Temperature Range: -40&deg;C to 85&deg;C | 获取价格 |
|
| LTC3026EMSE#TRPBF | Linear | 暂无描述 | 获取价格 |
|
| LTC3026EMSEPBF | Linear | 1.5A Low Input Voltage VLDO Linear Regulator | 获取价格 |
|
| LTC3026EMSETR | Linear | 1.5A Low Input Voltage VLDO Linear Regulator | 获取价格 |
|
| LTC3026EMSETRPBF | Linear | 1.5A Low Input Voltage VLDO Linear Regulator | 获取价格 |
|
| LTC3026_1 | Linear | 1.5A Low Input Voltage VLDO Linear Regulator | 获取价格 |
|
| LTC3026_1208 | Linear | 1.5A Low Input Voltage VLDO Linear Regulator | 获取价格 |
|
| LTC3035 | Linear | 300mA VLDO Linear Regulator with Charge Pump Bias Generator | 获取价格 |
|
| LTC3035 | ADI | 具有充电泵偏置发生器的 300mA VLDO 线性稳压器 | 获取价格 |
|
| LTC3035EDDB | Linear | 300mA VLDO Linear Regulator with Charge Pump Bias Generator | 获取价格 |
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