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PDF LT8610 Data sheet ( Hoja de datos )
| Número de pieza | LT8610 | |
| Descripción | 2.5A Synchronous Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT8610 (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
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FEATURES
n Wide Input Voltage Range: 3.4V to 42V
n Ultralow Quiescent Current Burst Mode® Operation:
2.5μA IQ Regulating 12VIN to 3.3VOUT
Output Ripple < 10mVP-P
n High Efficiency Synchronous Operation:
96% Efficiency at 1A, 5VOUT from 12VIN
94% Efficiency at 1A, 3.3VOUT from 12VIN
n Fast Minimum Switch-On Time: 50ns
n Low Dropout Under All Conditions: 200mV at 1A
n Allows Use Of Small Inductors
n Low EMI
n Adjustable and Synchronizable: 200kHz to 2.2MHz
n Current Mode Operation
n Accurate 1V Enable Pin Threshold
n Internal Compensation
n Output Soft-Start and Tracking
n Small Thermally Enhanced 16-Lead MSOP Package
APPLICATIONS
n Automotive and Industrial Supplies
n General Purpose Step-Down
n GSM Power Supplies
Electrical Specifications Subject to Change
LT8610
42V, 2.5A Synchronous
Step-Down Regulator
with 2.5µA Quiescent
Current
DESCRIPTION
The LT®8610 is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
that consumes only 2.5μA of quiescent current. Top and
bottom power switches are included with all necessary
circuitry to minimize the need for external components.
Low ripple Burst Mode operation enables high efficiency
down to very low output currents while keeping the output
ripple below 10mVP-P. A SYNC pin allows synchronization
to an external clock. Internal compensation with peak cur-
rent mode topology allows the use of small inductors and
results in fast transient response and good loop stability.
The EN/UV pin has an accurate 1V threshold and can be
used to program VIN undervoltage lockout or to shut down
the LT8610 reducing the input supply current to 1μA. A
capacitor on the TR/SS pin programs the output voltage
ramp rate during start-up. The PG flag signals when VOUT
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is within ±9% of the programmed output voltage as well
as fault conditions. The LT8610 is available in a small
16-lead MSOP package with exposed pad for low thermal
resistance.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
5V 2.5A Step-Down Converter
VIN
5.5V TO 42V
4.7μF
10nF
1μF
VIN BST
EN/UV
PG SW
LT8610
SYNC
BIAS
TR/SS
FB
INTVCC
RT PGND GND
60.4k
0.1μF
4.7μH
1M
10pF
243k
fSW = 700kHz
8610 TA01a
VOUT
5V
47μF 2.5A
100
95
90
85
80
75
70
65
60
55
50
0
12VIN to 5VOUT Efficiency
fSW = 700kHz
VIN = 12V
VIN = 24V
0.5 1 1.5 2
LOAD CURRENT (A)
2.5
8610 G01
8610p
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LT8610
No Load Supply Current
5.0
4.5
VOUT = 3.3V
IN REGULATION
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0 5 10 15 20 25 30 35 40 45
INPUT VOLTAGE (V)
8610 G10
Top FET Current Limit
5.0
4.5 30% DC
4.0
70% DC
3.5
3.0
2.5
–55 –25 5
35 65
TEMPERATURE (°C)
95 125
8610 G14
No Load Supply Current
25
VOUT = 3.3V
VIN = 12V
20 IN REGULATION
15
10
5
0
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
8610 G11
Bottom FET Current Limit
3.6
3.4
3.2
3.0
2.8
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2.6
2.4
–55 –25 5
35 65
TEMPERATURE (°C)
95 125
8610 G15
Top FET Current Limit vs Duty Cycle
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
0
0.2 0.4 0.6 0.8 1.0
DUTY CYCLE
8610 G13
Switch Drop
250
SWITCH CURRENT = 1A
200
150
TOP SW
100
BOT SW
50
0
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
8610 G40
Switch Drop
450
400
350
300
250
TOP SW
200
BOT SW
150
100
50
0
0 0.5 1 1.5 2 2.5 3
SWITCH CURRENT (A)
8610 G41
Minimum On-Time
80
ILOAD = 1A, VSYNC = 0V
75 ILOAD = 1A, VSYNC = 3V
70
ILOAD = 2.5A, VSYNC = 0V
ILOAD = 2.5A, VSYNC = 3V
65
60
55
50
45
40
35
30
–55 –25
5 35 65 95
TEMPERATURE (°C)
125 155
8610 G17
Minimum Off-Time
100
VIN = 3.3V
95 ILOAD = 0.5A
90
85
80
75
70
65
60
–50 –25
5 35 65 95
TEMPERATURE (°C)
125 155
8610 G18
8610p
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5 Page 
LT8610
APPLICATIONS INFORMATION
Achieving Ultralow Quiescent Current
To enhance efficiency at light loads, the LT8610 operates
in low ripple Burst Mode operation, which keeps the out-
put capacitor charged to the desired output voltage while
minimizing the input quiescent current and minimizing
output voltage ripple. In Burst Mode operation the LT8610
delivers single small pulses of current to the output capaci-
tor followed by sleep periods where the output power is
supplied by the output capacitor. While in sleep mode the
LT8610 consumes 1.7μA.
As the output load decreases, the frequency of single cur-
rent pulses decreases (see Figure 1a) and the percentage
of time the LT8610 is in sleep mode increases, resulting in
Burst Frequency
800
VIN = 12V
700 VOUT = 3.3V
600
500
400
300
200
100
0
0 50 100 150 200
LOAD CURRENT (mA)
(1a)
8610 F01a
Minimum Load to Full Frequency (SYNC DC High)
100
5VOUT
700kHz
80
60
much higher light load efficiency than for typical convert-
ers. By maximizing the time between pulses, the converter
quiescent current approaches 2.5μA for a typical application
when there is no output load. Therefore, to optimize the
quiescent current performance at light loads, the current
in the feedback resistor divider must be minimized as it
appears to the output as load current.
While in Burst Mode operation the current limit of the top
switch is approximately 400mA resulting in output voltage
ripple shown in Figure 2. Increasing the output capacitance
will decrease the output ripple proportionally. As load ramps
upward from zero the switching frequency will increase
but only up to the switching frequency programmed by
the resistor at the RT pin as shown in Figure 1a. The out-
put load at which the LT8610 reaches the programmed
frequency varies based on input voltage, output voltage,
and inductor choice.
For some applications it is desirable for the LT8610 to
operate in pulse-skipping mode, offering two major differ-
ences from Burst Mode operation. First is the clock stays
awake at all times and all switching cycles are aligned to
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the clock. In this mode much of the internal circuitry is
awake at all times, increasing quiescent current to several
hundred μA. Second is that full switching frequency is
reached at lower output load than in Burst Mode operation
(see Figure 1b). To enable pulse-skipping mode, the SYNC
pin is tied high either to a logic output or to the INTVCC
pin. When a clock is applied to the SYNC pin the LT8610
will also operate in pulse-skipping mode.
IL
200mA/DIV
40
20
0
5 10 15 20 25 30 35 40 45
INPUT VOLTAGE (V)
(1b)
8610 F01b
Figure 1. SW Frequency vs Load Information in
Burst Mode Operation (1a) and Pulse-Skipping Mode (1b)
VOUT
10mV/DIV
VSYNC = 0V
5μs/DIV
8610 F02
Figure 2. Burst Mode Operation
8610p
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11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LT8610.PDF ] | |
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