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PDF LTC3026 Data sheet ( Hoja de datos )
| Número de pieza | LTC3026 | |
| Descripción | 1.5A Low Input Voltage VLDO Linear Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Features
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 IOUT = 1.5A
n Adjustable Output Range: 0.4V to 2.6V
n Output Current: Up to 1.5A
n Excellent Supply Rejection Even Near Dropout
n Shutdown Disconnects Load from VIN and VBST
n Low Operating Current: IIN = 950µA at VIN = 1.5V
n Low Shutdown Current:
IIN < 1µA (Typ), IBST = 0.1µA (Typ)
n Stable with 10µF or Greater Ceramic Capacitors
n Short-Circuit, Reverse Current Protected
n Overtemperature Protected
n Available in 10-Lead MSOP and 10-Lead
(3mm × 3mm) DFN Packages
Applications
n High Efficiency Linear Regulator
n Post Regulator for Switching Supplies
n Microprocessor Supply
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT, VLDO are trademarks of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
LTC3026www.DataSheet4U.com
1.5A Low Input Voltage
VLDO Linear Regulator
Description
The LTC®3026 is a very low dropout (VLDO™) linear regula-
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.
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.
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.
Typical Application
1.2V Output Voltage from 1.5V Input Supply
VIN = 1.5V
L1
10µH
SW
5V BOOST BST
CONVERTER
IN
4.7µF
0.4V +
–
OUT
OFF ON
SHDN
GND
LTC3026
ADJ
PG
L1: MURATA LQH2MCN100K02
4.7µF
8.06k
100k 4.02k
VOUT = 1.2V,
1.5A
COUT
10µF
3026 TA01a
Dropout Voltage vs Output Current
150
100
1.2V
1.5V
2.0V
2.6V
50
0
0 0.5 1.0 1.5
IOUT (A)
3026 TA01b
3026fd
1 page  
Typical Performance Characteristics
LTC3026www.DataSheet4U.com
ADJ Voltage vs Temperature
404
403
402
401 1mA
400
399 1.5A
398
397
396
–50 –25
VBST = 5V
VIN = 1.5V
VOUT =1.2V
0 25 50 75
TEMPERATURE (°C)
100 125
3026 G04
IN Shutdown Current
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5 3.5V
1.0
0.5
0
–50
2.5V
1.2V
–25 0 25 50 75 100 125
TEMPERATURE (°C)
3026 G05
BST Voltage vs Temperature
5.050
VIN = 1.5V
5.025
5.000
4.975
4.950
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3026 G06
Dropout Voltage vs Input Voltage
200
180
VFB = 0.38V
IOUT =1.5A
160
140
120
100
80
60
40
–40°C
25°C
20
85°C
125°C
0
1.2
1.4
1.6 1.8 2.0
2.2
2.4
2.6
VIN (V)
3026 G07
Ripple Rejection
60
10kHz
50
1MHz
40
100kHz
30
20
10
0
1.2 1.4
VBST = 5V
VOUT =1.2V
IOUT = 800mA
COUT = 10µF
1.6 1.8 2.0 2.2 2.4 2.6
VIN (V)
3026 G08
Ripple Rejection
70
60
50
40
30
20
10
0
100
1000
VBST = 5V
VIN = 1.5V
VOUT =1.2V
IOUT = 800mA
COUT = 10µF
10000 100000 1000000 1E+07
FREQUENCY (Hz)
3026 G09
Shutdown Threshold
1200
900
600
300
1
2
34
VIN (V)
RISE
RISE
FALL
FALL
RISE
FALL
–40°C
25°C
125°C
56
3026 G10
Output Current Limit
5.0
4.5
VOUT = 0V
TA = 25°C
4.0
3.5
3.0
2.5
CURRENT LIMIT
2.0
1.5
THERMAL LIMIT
1.0
1.0 1.5 2.0 2.5 3.0 3.5
VIN (V)
3026 G11
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
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3026 G12
3026fd
5 Page 
Operation
The LTC3026 operates at a relatively high gain of
270µV/A referred 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.
Power Good Operation
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 im-
pedance 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 regula-
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. VIN should be the
minimum operating voltage (1.14V) or greater for PG to
function correctly.
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.
LTC3026www.DataSheet4U.com
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.
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
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.
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
X5R
–20
–40
–60
Y5V
–80
–100 0
123 45 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 –25
0
25 50
TEMPERATURE (°C)
75
3026 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
3026fd
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LTC3026.PDF ] | |
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