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PDF LTC3714 Data sheet ( Hoja de datos )
| Número de pieza | LTC3714 | |
| Descripción | Wide Operating Range / Step-Down Controller with Internal Op Amp | |
| Fabricantes | Linear | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC3714 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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LTC3714
FEATURES
Intel Compatible,
Wide Operating Range, Step-Down Controller
with Internal Op Amp
DESCRIPTIO
s True Current Mode with Ultrafast Transient
Response
s Stable with Ceramic COUT
s tON(MIN) < 100ns for Operation from High Input
Ranges
s Supports Active Voltage Positioning
s No Sense Resistor Required
s 5-Bit VID Programmable Output Voltage: 0.6V to 1.75V
s Dual N-Channel MOSFET Synchronous Drive
s Programmable Output Offsets
s Power Good Output Voltage Monitor
s Wide VIN Range: 4V to 36V
s ±1% 0.6V Reference
s Adjustable Frequency
s Programmable Soft-Start
s Output Overvoltage Protection
s Optional Short-Circuit Shutdown Timer
s Forced Continuous Control Pin
s Logic Controlled Micropower Shutdown: IQ ≤ 30µA
s Available in 0.209" Wide 28-Lead SSOP Package
U
APPLICATIO S
s Power Supply for Mobile Pentium® Processors and
Transmeta Processors
s Notebook and Portable Computers
The LTC®3714 is a synchronous step-down switching
regulator controller for CPU power. An output voltage
between 0.6V and 1.75V is selected by a 5-bit code (Intel
mobile VID specification). The controller uses a constant
on-time, valley current control architecture to deliver very
low duty cycles without requiring a sense resistor. Oper-
ating frequency is selected by an external resistor and is
compensated for variations in VIN and VOUT.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
when the main output is lightly loaded. Internal op amp
allows programmable offsets to the output voltage during
power saving modes.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is user pro-
grammable. Wide supply range allows operation from 4V
to 36V at the input.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
TYPICAL APPLICATIO
INTVCC
CSS
0.1µF
CC RC
5-BIT
VID
*OPTIONAL
LTC3714
PGOOD ION
VIN
RUN/SS TG
ITH SW
BOOST
SGND
VID4
VID3
VID2
VID1
VID0
INTVCC
BG
SENSE
PGND
RON
CB, 0.22µF
DB
CMDSH-3
+
CVCC
4.7µF
M1
IRF7811 L1
×2 0.68µH
M2
IRF7811
×3
0.003Ω*
D1*
UPS840
VIN
10µF 5V TO 24V
35V
×4
VOUT
0.6V TO 1.75V
+ COUT 23A
270µF
2V
×4
VOSENSE
3714 F01
Figure 1. High Efficiency Step-Down Converter
Transient Response of 8A to 23A Output Load Step
20µs/DIV
1.395V
VOUT
(1.35V)
50mV/DIV
1.213V
23A
ILOAD
10A/DIV
8A
3714 TA03
3714f
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response
Transient Response
(Discontinuous Mode)
LTC3714
Start-Up
VOUT
50mV/DIV
IL
5A/DIV
VOUT
50mV/DIV
IL
5A/DIV
RUN/SS
2V/DIV
VOUT
500mV/DIV
IL
5A/DIV
20µs/DIV
LOAD STEP 0A TO 10A
VIN = 15V
VOUT = 1.5V
FCB = 0V
FIGURE 1 CIRCUIT
3714 G01
Efficiency vs Load Current
95
90 VIN = 8.5V
85 VIN = 15V
80 VIN = 24V
75 VOUT = 1.35V
FREQUENCY = 300kHz
FIGURE 1 CIRCUIT
70
0 3 6 9 12 15 18 21
LOAD CURRENT (A)
3714 G03
Load Regulation
0
NO AVP
FIGURE 1 CIRCUIT
–0.1
–0.2
–0.3
–0.4
0
2 4 68
LOAD CURRENT (A)
10
3714 G06
20µs/DIV
LOAD STEP 1A TO 10A
VIN = 15V
VOUT = 1.5V
FCB = INTVCC
FIGURE 1 CIRCUIT
3714 G02
Efficiency vs Input Voltage
100
90
IOUT = 10A
80
IOUT = 1A
70 IOUT = 23A
60
0
5 10 15 20 25
INPUT VOLTAGE (V)
30
3714 G04
ITH Voltage vs Load Current
2.5
FIGURE 1 CIRCUIT
2.0
1.5
CONTINUOUS
MODE
1.0
DISCONTINUOUS
0.5 MODE
0
0 5 10
LOAD CURRENT (A)
15
3714 G07
VIN = 15V
VOUT = 1.25V
RLOAD = 0.125Ω
50ms/DIV
3714 G19
Frequency vs Input Voltage
300
FCB = 0V
FIGURE 1 CIRCUIT
280
IOUT = 10A
260
240 IOUT = 0A
220
200
5
10 15 20
INPUT VOLTAGE (V)
25
3714 G05
Current Sense Threshold
vs ITH Voltage
300
VRNG =
2V
200 1.4V
1V
100 0.7V
0.5V
0
–100
–200
0
0.5 1.0 1.5 2.0
ITH VOLTAGE (V)
2.5 3.0
3714 G08
3714f
5
5 Page 
U
OPERATIO
Internal Op Amp
The internal op amp allows the user to program accurate
offsets to the output voltage during power saving modes.
By connecting the OP+ pin to the output, the OPOUT pin to
the VOSENSE pin and an external resistor R1 between the
OP–and OPOUT pins, the op amp is hooked up as a unity-
gain feedback amplifier. Resistors R2 and R3, together
with series switches, can then be placed on the OP– pin to
allow negative offsets to be switched onto the output
voltage (see Figures 2a and 2b). The accuracy of the offset
will depend on the matching of the external resistors R1 to
R2 and R3.*
For applications that require less accurate output offsets,
or none at all, the user can use the internal op amp for true
differential remote sensing of the output voltage by con-
necting OPOUT to VOSENSE and using OP + and OP – for
differential sensing across the output capacitor as shown
in Figure 2c.
LTC3714
INTVCC/EXTVCC Power
Power for the top and bottom MOSFET drivers and most
of the internal controller circuitry is derived from the
INTVCC pin. The top MOSFET driver is powered from a
floating bootstrap capacitor CB. This capacitor is re-
charged from INTVCC through an external Schottky diode
DB when the top MOSFET is turned off. When the EXTVCC
pin is grounded, an internal 5V low dropout regulator
supplies the INTVCC power from VIN. If EXTVCC rises
above 4.7V, the internal regulator is turned off, and an
internal switch connects EXTVCC to INTVCC. This allows
a high efficiency source connected to EXTVCC, such as an
external 5V supply or a secondary output from the
converter, to provide the INTVCC power. Voltages up to
7V can be applied to EXTVCC for additional gate drive. If
the input voltage is low and INTVCC drops below 3.5V,
undervoltage lockout circuitry prevents the power
switches from turning on.
*An alternate configuration, shown in Figure 2b, can be used to program
offsets as well. Either configuration can be used, depending upon the logic
of control signals. If offsets are not required, the op amp can be used to
remotely sense the output voltage, proving true differential sense.
VOUT
OP+
17
OP– 16
15 OPVIN
+ OPOUT
18
–
R1
VOSENSE
23
VID DAC
VFB
22
SLEEP
MODE
OFFSET
R2
BATTERY
MODE
OFFSET
R3
Figure 2a
3714 F02b
BATTERY
MODE
OFFSET
VOUT
R1 OP+
17
R2
OP– 16
R2
SLEEP
MODE
OFFSET
R3
15 OPVIN
+
VID DAC
18 23
– VFB
22
R1
3714 F02b
Figure 2b
VOUT+
R
R
VOUT–
R
OP+
17
OP– 16
15 OPVIN
+ OPOUT VOSENSE
18 23
–
R
Figure 2c
3714 F02c
3714f
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC3714.PDF ] | |
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