|
|
PDF LT8705 Data sheet ( Hoja de datos )
| Número de pieza | LT8705 | |
| Descripción | 80V VIN and VOUT Synchronous 4-Switch Buck-Boost DC/DC Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT8705 (archivo pdf) en la parte inferior de esta página. Total 44 Páginas | ||
|
No Preview Available !
Electrical Specifications Subject to Change
LT8705
80V VIN and VOUT
Synchronous 4-Switch Buck-
Boost DC/DC Controller
FEATURES
n Single Inductor Allows VIN Above, Below, or Equal
to Regulated VOUT
n VIN Range 2.8V (Need EXTVCC > 6.4V) to 80V
n VOUT Range: 1.3V to 80V
n Quad N-Channel MOSFET Gate Drivers
n Synchronous Rectification: Up to 98% Efficiency
n Input and Output Current Monitor Pins
n Synchronizable Fixed Frequency: 100kHz to 400kHz
n Integrated Input Current, Input Voltage, Output
Current and Output Voltage Feedback Loops
n Clock Output Usable To Monitor Die Temperature
n Available in 38-Lead (5mm × 7mm) QFN and TSSOP
Packages with the TSSOP Modified for Improved
High Voltage Operation
APPLICATIONS
n High Voltage Buck-Boost Converters
n Input or Output Current Limited Converters
DESCRIPTION
The LT®8705 is a high performance buck-boost switch-
ing regulator controller that operates from input voltages
above, below or equal to the output voltage. The part has
integrated input current, input voltage, output current
and output voltage feedback loops. With a wide 2.8V to
80V input and 1.3V to 80V output range, the LT8705 is
compatible with most solar, automotive, telecom and
battery-powered systems.
The operating mode of the controller is determined
through the MODE pin. The MODE pin can select among
discontinuous mode, forced continuous mode and Burst
Mode® operation. The LT8705 also features programmable
UVLO and switching currents, along with input and output
current monitoring with programmable maximum levels.
L, LT, LTC, LTM, Linear Technology, Burst Mode, µModule and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
http://www.DataSheet4U.com/
TYPICAL APPLICATION
Telecom Voltage Stabilizer
VIN
36V TO
80V
1µF
+ 220µF
×2
M1
×2
4.7µF
×4
TO
DIODE
0.22µF
2Ω
×2
22µH
M2
M3
×2
1nF 10Ω 10mΩ
1nF 10Ω
2Ω
×2
M4
TO
DIODE
0.22µF
TG1 BOOST1 SW1 BG1 CSP
CSNIN
CSN
GND BG2 SW2 BOOST2 TG2
CSPOUT
CSPIN
CSNOUT
100k
VIN
SHDN
SWEN
LDO33
MODE
LT8705
EXTVCC
FBOUT
INTVCC
GATEVCC
SRVO_FBIN
FBIN SRVO_FBOUT
RT SRVO_IIN
71.5k
SS
SRVO_IOUT
IMON_IN
20k
4.7µF
VC
215k 56.2k
1µF 220pF
3.3nF
CLKOUT
202kHz
SYNC
IMON_OUT
4.7µF
×6
VOUT
+
48V
220µF 5A
×2
392k
10k
4.7µF
4.7µF
4Ω
TO TO
BOOST1 BOOST2
Efficiency and Power Loss
100 6
5
95
4
90 3
2
85
VOUT = 48V 1
ILOAD = 2A
80 0
30 40 50 60 70 80
VIN (V)
8705 TA01b
8705 TA01
For more information www.linear.com/8705
8705p
1
1 page  
LT8705
E LECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, SHDN = 3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
CSPOUT, CSNOUT Bias Current
BOOST Capacitor Charge Control Block Not Active
ICSPOUT + ICSNOUT, VCSPOUT = VCSNOUT = 12V
ICSPOUT + ICSNOUT, VCSPOUT = VCSNOUT = 1.5V
CSPOUT, CSNOUT Common Mode Operating Voltage Range
l0
45
4
80
µA
µA
V
CSPOUT, CSNOUT Differential Mode Operating Voltage Range
l –100
100 mV
VCSPOUT-CSNOUT to IMON_OUT Amplifier A6 gm
IMON_OUT Maximum Output Current
VCSPOUT – VCSNOUT = 50mV, VCSPOUT = 5.052V
VCSPOUT – VCSNOUT = 50mV, VCSPOUT = 5.025V
VCSPOUT – VCSNOUT = 5mV, VCSPOUT = 5.0025V
VCSPOUT – VCSNOUT = 5mV, VCSPOUT = 5.0025V
0.95
l 0.94
0.65
l 0.55
l 100
1 1.05 mmho
1 1.085 mmho
1 1.35 mmho
1 1.6 mmho
µA
IMON_OUT Overvoltage Threshold
l 1.55 1.61 1.67
V
IMON_OUT Error Amp EA1 gm
IMON_OUT Error Amp EA1 Voltage Gain
185 µmho
130 V/V
SRVO_IIN Activation Threshold (Note 5)
SRVO_IIN Activation Threshold Hysteresis (Note 5)
SRVO_IOUT Activation Threshold (Note 5)
SRVO_IOUT Activation Threshold Hystersis (Note 5)
SRVO_IIN, SRVO_IOUT Low Voltage (Note 5)
(VIMON_IN Rising) – (Regulation Voltage for
IMON_IN), VFBIN = 3V, VFBOUT = 0V, VIMON_OUT = 0V
–60 –49 –37
VFBIN = 3V, VFBOUT = 0V, VIMON_OUT = 0V
22
(VIMON_OUT Rising) – (Regulation Voltage for IMON_
OUT), VFBIN = 3V, VFBOUT = 0V, VIMON_IN = 0V
–62 –51 –39
VFBIN = 3V, VFBOUT = 0V, VIMON_IN = 0V
22
I = 100μA
l 110 330
mV
mV
mV
mV
mV
SRVO_IIN, SRVO_IOUT Leakage Current (Note 5)
NMOS Gate Drivers
VSRVO_IIN = VSRVO_IOUT = 2.5V
http://www.DataSheet4U.com/
l
01
µA
TG1, TG2 Rise Time
TG1, TG2 Fall Time
BG1, BG2 Rise Time
BG1, BG2 Fall Time
TG1 Off to BG1 On Delay
BG1 Off to TG1 On Delay
TG2 Off to BG2 On Delay
BG2 Off to TG2 On Delay
Minimum On-Time for Main Switch in Boost Operation
(tON(M3,MIN))
Minimum On-Time for Synchronous Switch in Buck
Operation (tON(M2,MIN))
Minimum Off-Time for Main Switch in Steady-State Boost
Operation
CLOAD = 3300pF (Note 4)
CLOAD = 3300pF (Note 4)
CLOAD = 3300pF (Note 4)
CLOAD = 3300pF (Note 4)
CLOAD = 3300pF Each Driver
CLOAD = 3300pF Each Driver
CLOAD = 3300pF Each Driver
CLOAD = 3300pF Each Driver
Switch M3, CLOAD = 3300pF
Switch M2, CLOAD = 3300pF
Switch M3, CLOAD = 3300pF
20 ns
20 ns
20 ns
20 ns
100 ns
80 ns
100 ns
80 ns
265 ns
260 ns
245 ns
Minimum Off-Time for Synchronous Switch in
Steady-State Buck Operation
Switch M2, CLOAD = 3300pF
245 ns
Oscillator
Switch Frequency Range
SYNCing or Free Running
100 400 kHz
Switching Frequency, fOSC
RT = 365k
RRTT
=
=
215k
124K
l 102 120 142
l 170 202 235
l 310 350 400
kHz
kHz
kHz
For more information www.linear.com/8705
8705p
5
5 Page 
LT8705
PIN FUNCTIONS (QFN/TSSOP)
SHDN (Pin 1/Pin 4): Shutdown Pin. Tie high to enable
device. Ground to shut down and reduce quiescent current
to a minimum. Do not float this pin.
RT (Pin 12/Pin 15): Timing Resistor Pin. Adjusts the switch-
ing frequency. Place a resistor from this pin to ground to
set the free-running frequency. Do not float this pin.
CSN (Pin 2/Pin 5): The (–) Input to the Inductor Current
Sense and Reverse-Current Detect Amplifier.
CSP (Pin 3/Pin 6): The (+) Input to the Inductor Current
Sense and Reverse-Current Detect Amplifier. The VC pin
voltage and built-in offsets between CSP and CSN pins, in
conjunction with the RSENSE resistor value, set the current
trip threshold.
LDO33 (Pin 4/Pin7): 3.3V Regulator Output. Bypass this
pin to ground with a minimum 0.1μF ceramic capacitor.
FBIN (Pin 5/Pin 8): Input Feedback Pin. This pin is con-
nected to the input error amplifier input.
FBOUT (Pin 6/Pin 9): Output Feedback Pin. This pin
connects the error amplifier input to an external resistor
divider from the output.
IMON_OUT (Pin 7/Pin 10): Output Current Monitor Pin. The
current out of this pin is proportional to the output current.
See the Operation and Applications Information sections.
VC (Pin 8/Pin 11): Error Amplifier Output Pin. Tie external
compensation network to this pin.
SS (Pin 9/Pin 12): Soft-Start Pin. Place at least 100nF of
capacitance here. Upon start-up, this pin will be charged
by an internal resistor to 2.5V.
CLKOUT (Pin 10/Pin 13): Clock Output Pin. Use this pin to
synchronize one or more compatible switching regulator
ICs to the LT8705. CLKOUT toggles at the same frequency
as the internal oscillator or as the SYNC pin, but is ap-
proximately 180° out of phase. CLKOUT may also be used
as a temperature monitor since the CLKOUT duty cycle
varies linearly with the part’s junction temperature. The
CLKOUT pin can drive capacitive loads up to 200pF.
SYNC (Pin 11/Pin 14): To synchronize the switching fre-
quency to an outside clock, simply drive this pin with a
clock. The high voltage level of the clock needs to exceed
1.3V, and the low level should be less than 0.5V. Drive this
pin to less than 0.5V to revert to the internal free-running
clock. See the Applications Information section for more
information.
BG1, BG2 (Pins 14, 16/Pins 17, 19): Bottom Gate Drive.
Drives the gates of the bottom N-channel MOSFETs be-
tween ground and GATEVCC.
GATEVCC (Pin 15/Pin 18): Power Supply for Gate Drivers.
Must be connected to the INTVCC pin. Do not power from
any other supply. Locally bypass to GND.
BOOST1, BOOST2 (Pins 23, 17/Pins 28, 20): Boosted
Floating Driver Supply. The (+) terminal of the bootstrap
capacitor connects here. The BOOST1 pin swings from a
diode voltage below GATEVCC up to VIN + GATEVCC. The
BOOST2 pin swings from a diode voltage below GATEVCC
up to VOUT + GATEVCC
TG1, TG2 (Pins 22, 18/Pins 26, 21): Top Gate Drive. Drives
the top N-channel MOSFETs with voltage swings equal
to GATEVCC superimposed on the switch node voltages.
SW1, SW2 (Pins 21, 19/Pins 24, 22): Switch Nodes. The
(–)http://www.DataSheet4U.com/ terminals of the bootstrap capacitors connect here.
SRVO_FBIN (Pin 25 QFN Only): Open-Drain Logic Out-
put. This pin is pulled to ground when the input voltage
feedback loop is active.
SRVO_IIN (Pin 26 QFN Only): Open-Drain Logic Output.
The pin is pulled to ground when the input current loop
is active.
SRVO_IOUT (Pin 27 QFN Only): Open-Drain Logic Out-
put. The pin is pulled to ground when the output current
feedback loop is active.
SRVO_FBOUT (Pin 28 QFN Only): Open-Drain Logic Out-
put. This pin is pulled to ground when the output voltage
feedback loop is active.
EXTVCC (Pin 29/Pin 30): External VCC Input. When EXTVCC
exceeds 6.4V (typical), INTVCC will be powered from this
pin. When EXTVCC is lower than 6.22V (typical), INTVCC
will be powered from VIN.
CSNOUT (Pin 30/Pin 32): The (–) Input to the Output Cur-
rent Monitor Amplifier. Connect this pin to VOUT when not
in use. See Applications Information section for proper
use of this pin.
8705p
For more information www.linear.com/8705
11
11 Page | ||
| Páginas | Total 44 Páginas | |
| PDF Descargar | [ Datasheet LT8705.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT8705 | 80V VIN and VOUT Synchronous 4-Switch Buck-Boost DC/DC Controller | Linear Technology |
| LT8709 | Negative Input Synchronous Multi-Topology DC/DC Controller |  Linear |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |