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PDF LTC3129 Data sheet ( Hoja de datos )
| Número de pieza | LTC3129 | |
| Descripción | 200mA Synchronous Buck-Boost DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3129
15V, 200mA Synchronous
Buck-Boost DC/DC Converter
with 1.3µA Quiescent Current
Features
Description
n Regulates VOUT Above, Below or Equal to VIN
n Wide VIN Range: 2.42V to 15V, 1.92V to 15V After
Start-Up (Bootstrapped)
n Wide VOUT Range: 1.4V to 15.75V
n 200mA Output Current in Buck Mode
n Single Inductor
n 1.3µA Quiescent Current
n Programmable Maximum Power Point Control
n 1.2MHz Ultralow Noise PWM
n Current Mode Control
n Pin Selectable Burst Mode® Operation
n Up to 95% Efficiency
n Accurate RUN Pin Threshold
n Power Good Indicator
n 10nA Shutdown Current
n Thermally Enhanced 3mm × 3mm QFN and
16-Lead MSOP Packages
Applications
n Industrial Wireless Sensor Nodes
n Post-Regulator for Harvested Energy
n Solar Panel Post-Regulator/Charger
n Intrinsically Safe Power Supplies
n Wireless Microphones
n Avionics-Grade Wireless Headsets
The LTC®3129 is a high efficiency, 200mA buck-boost
DC/DC converter with a wide VIN and VOUT range. It includes
an accurate RUN pin threshold to allow predictable regula-
tor turn-on and a maximum power point control (MPPC)
capability that ensures maximum power extraction from
non-ideal power sources such as photovoltaic panels.
The LTC3129 employs an ultralow noise, 1.2MHz PWM
switching architecture that minimizes solution footprint by
allowing the use of tiny, low profile inductors and ceramic
capacitors. Built-in loop compensation and soft-start
simplify the design. For high efficiency operation at light
loads, automatic Burst Mode operation can be selected,
reducing the quiescent current to just 1.3µA.
Additional features include a power good output, less than
10nA of shutdown current and thermal shutdown.
The LTC3129 is available in thermally enhanced 3mm ×
3mm QFN and 16-lead MSOP packages. For fixed output
voltage options, see the functionally equivalent LTC3129-1,
which eliminates the need for an external feedback divider.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Typical Application
22nF 10µH 22nF
2.42V TO 15V
VIN
10µF
VCC
BST1 SW1
VIN
SW2 BST2
VOUT
LTC3129
RUN
MPPC
PWM
FB
PGOOD
VCC
GND PGND
5V AT 200mA, VIN > 5V
5V AT 100mA, VIN < 5V
VOUT
10µF 10pF
3.32M
1.02M
2.2µF
3129 TA01a
Efficiency and Power Loss vs Load
100 1000
90 EFFICIENCY
80 100
70
60 10
50 POWER LOSS
40 1
30
20
10
0 VOUT = 5V
0.01 0.1
1
VIN = 2.5V
VIN = 3.6V
0.1
VIN = 5V
VIN = 15V 0.01
10 100 1000
OUTPUT CURRENT (mA)
3129 TA01b
3129fc
For more information www.linear.com/LTC3129
1
1 page  
LTC3129
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
Power Loss, VOUT = 3.3V
1000
100 PWM
10
1
0.1
0.01
0.01
BURST
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G04
Efficiency, VOUT = 5V
100
90 BURST
80
70
60
50
PWM
40
30
20
10
0
0.01
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G05
Power Loss, VOUT = 5V
1000
100 PWM
10
1
0.1
0.01
0.01
BURST
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G06
Efficiency, VOUT = 12V
100
90 B4U0RST
80
70
60
50
PWM
40
30
20
10
0
0.01
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G07
Power Loss, VOUT = 12V
1000
100 PWM
10
1
0.1
0.01
0.01
BURST
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G08
Power Loss, VOUT = 15V
1000
100 PWM
Maximum Output Current
vs VIN and VOUT
250
200
10
1
0.1
0.01
0.01
BURST
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1
10 100 1000
OUTPUT CURRENT (mA)
3129 G10
150
VOUT = 2.5V
100
VOUT = 3.3V
VOUT = 4.1V
VOUT = 5V
50
VOUT = 6.9V
VOUT = 8.2V
VOUT = 12V
0 VOUT = 15V
2 3 4 5 6 7 8 9 10 11 12 13 14 15
VIN (V)
3129 G11
For more information www.linear.com/LTC3129
Efficiency, VOUT = 15V
100
90 BURST
80
70
60
50
40 PWM
30
20
10
0
0.01
VIN = 2.5V
VIN = 3.6V
VIN = 5V
VIN = 10V
VIN = 15V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
3129 G09
No Load Input Current
vs VIN and VOUT (PWM = 0V)
30 VOUT = 2.5V
25
VOUT = 5V
VOUT = 10V
VOUT = 15V
20 FB DIVIDER CURRENT = 2µA
15
10
5
0
2.5 4.5 6.5 8.5 10.5 12.5 14.5
VIN (V)
3129 G12
3129fc
5
5 Page 
LTC3129
Operation
When stepping down from a high input voltage to a lower
output voltage, the converter operates in buck mode and
switch D remains on for the entire switching cycle except
for the minimum switch low duration (typically 90ns). Dur-
ing the switch low duration, switch C is turned on which
forces SW2 low and charges the flying capacitor, CBST2.
This ensures that the switch D gate driver power supply
rail on BST2 is maintained. The duty cycle of switches A
and B are adjusted to maintain output voltage regulation
in buck mode.
If the input voltage is lower than the output voltage, the
converter operates in boost mode. Switch A remains on
for the entire switching cycle except for the minimum
switch low duration (typically 90ns). During the switch
low duration, switch B is turned on which forces SW1
low and charges the flying capacitor, CBST1. This ensures
that the switch A gate driver power supply rail on BST1 is
maintained. The duty cycle of switches C and D are adjusted
to maintain output voltage regulation in boost mode.
Oscillator
The LTC3129 operates from an internal oscillator with a
nominal fixed frequency of 1.2MHz. This allows the DC/DC
converter efficiency to be maximized while still using small
external components.
Current Mode Control
The LTC3129 utilizes average current mode control for the
pulse width modulator. Current mode control, both average
and the better known peak method, enjoy some benefits
compared to other control methods including: simplified
loop compensation, rapid response to load transients and
inherent line voltage rejection.
Referring to the Block Diagram, a high gain, internally
compensated transconductance amplifier monitors Vout
through a voltage divider connected to the FB pin. The
error amplifier output is used by the current mode control
loop to command the appropriate inductor current level.
The inverting input of the internally compensated average
current amplifier is connected to the inductor current
sense circuit. The average current amplifier's output is
compared to the oscillator ramps, and the comparator
outputs are used to control the duty cycle of the switch
pins on a cycle-by-cycle basis.
The voltage error amplifier monitors the output voltage,
VOUT through a voltage divider and makes adjustments to
the current command as necessary to maintain regulation.
The voltage error amplifier therefore controls the outer
voltage regulation loop. The average current amplifier
makes adjustments to the inductor current as directed by
the voltage error amplifier output via VC and is commonly
referred to as the inner current loop amplifier.
The average current mode control technique is similar to
peak current mode control except that the average current
amplifier, by virtue of its configuration as an integrator,
controls average current instead of the peak current. This
difference eliminates the peak to average current error
inherent to peak current mode control, while maintaining
most of the advantages inherent to peak current mode
control.
Average current mode control requires appropriate com-
pensation for the inner current loop, unlike peak current
mode control. The compensation network must have high
DC gain to minimize errors between the actual and com-
manded average current level, high bandwidth to quickly
change the commanded current level following transient
load steps and a controlled mid-band gain to provide a
form of slope compensation unique to average current
mode control. The compensation components required
to ensure proper operation have been carefully selected
and are integrated within the LTC3129.
Inductor Current Sense and Maximum Output Current
As part of the current control loop required for current
mode control, the LTC3129 includes a pair of current
sensing circuits that measure the buck-boost converter
inductor current.
The voltage error amplifier output, VC, is internally clamped
to a nominal level of 0.6V. Since the average inductor
current is proportional to VC, the 0.6V clamp level sets
the maximum average inductor current that can be pro-
grammed by the inner current loop. Taking into account
the current sense amplifier's gain, the maximum average
For more information www.linear.com/LTC3129
3129fc
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3129.PDF ] | |
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