|
|
PDF NCP1575 Data sheet ( Hoja de datos )
| Número de pieza | NCP1575 | |
| Descripción | Low Voltage Synchronous Buck Controller | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de NCP1575 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
www.DataSheet4U.com
NCP1575
Low Voltage Synchronous
Buck Controller with
Adjustable Switching
Frequency
The NCP1575 is a low voltage buck controller. It provides the
control for a DC−DC power solution producing an output voltage as
low as 0.980 V over a wide current range. It contains all required
circuitry for a synchronous NFET buck regulator using the V2t
control method to achieve the fastest possible transient response and
best overall regulation. The NCP1575 operates at a default switching
frequency of 200 kHz, but switching frequency is user−programmable
with an additional resistor between ROSC and ground. This device
provides undervoltage lockout protection, soft−start, and built−in
adaptive nonoverlap and is assembled in an SOIC−8 package.
The NCP1575−based solution requires a bias supply of 12 V, and it
can convert from a bulk power supply ranging from 2 V to 12 V.
Conversion from bulk supplies greater than 7 V is best accomplished
by using an external doubler circuit to raise the enhancement voltage
for the external NFET switches.
Features
• Pb−Free Packages are Available
• 0.980 V ±1.0% Reference Voltage
• V2 Control Topology
• 200 ns Transient Response
• Programmable Soft−Start
• 40 ns Gate Rise and Fall Times (3.3 nF Load)
• Adaptive FET Nonoverlap Time
• Default 200 kHz Oscillator Frequency (No External
Resistor Required)
• User−Programmable Oscillator Frequency (One External
Resistor Required)
• Undervoltage Lockout
• On/Off Control Through Use of the COMP Pin
• Overvoltage Protection through Synchronous MOSFETs
• Synchronous N−Channel Buck Design
• “12 V Only” or Dual Supply Operation
http://onsemi.com
8
1
SOIC−8
D SUFFIX
CASE 751
MARKING
DIAGRAM
8
1575
ALYW
1
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
PIN CONNECTIONS
1
VCC
ROSC
NC
COMP
8
GND
VFB
GATE(L)
GATE(H)
ORDERING INFORMATION
Device
Package
Shipping†
NCP1575D
NCP1575DG
SOIC−8
SOIC−8
(Pb−Free)
98 Units/Rail
98 Units/Rail
NCP1575DR2 SOIC−8
NCP1575DR2G SOIC−8
(Pb−Free)
2500 Tape & Reel
2500 Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2004
November, 2004 − Rev. 6
1
Publication Order Number
NCP1575/D
1 page  
NCP1575
ELECTRICAL CHARACTERISTICS (0°C < TJ < 125°C, 9.0 V < VCC < 20 V, CGATE(H) = CGATE(L) = 3.3 nF,
CCOMP = 0.1 mF, ROSC = 74 kW; unless otherwise specified.) Note 3
Characteristic
Test Conditions
Min Typ
GATE(H) and GATE(L)
Rise Time
Fall Time
GATE(H) to GATE(L) Delay
1.0 V < GATE(L), GATE(H) < VCC − 2.0 V,
VCC = 12 V
VCC − 2.0 V < GATE(L), GATE(H) < 1.0 V,
VCC = 12 V
GATE(H) < 2.0 V, GATE(L) > 2.0 V
− 40
− 40
40 60
GATE(L) to GATE(H) Delay
GATE(L) < 2.0 V, GATE(H) > 2.0 V
40 60
Minimum Pulse Width
GATE(X) = 4.0 V
− 250
High Voltage (AC)
Low Voltage (AC)
GATE(H)/(L) Pull−Down
Measure GATE(L) or GATE(H)
0.5 nF < CGATE(H) = CGATE(L) < 10 nF, Note 4
Measure GATE(L) or GATE(H)
0.5 nF < CGATE(H) = CGATE(L) < 10 nF, Note 4
Resistance to GND. Note 4
VCC −
0.5
−
20
VCC
0
50
PWM Comparator
PWM Comparator Offset
VFB = 0 V, Increase COMP Until GATE(H)
Starts Switching
0.415 0.465
Ramp Max Duty Cycle
− − 80
Artificial Ramp
Transient Response
VFB Input Range
Oscillator
Duty Cycle = 50%, ROSC = 74 kW
COMP = 1.5 V, VFB 20 mV Overdrive. Note 4
Note 4
50 63
− 200
0−
Switching Frequency
ROSC Not Used
ROSC = 74 kW
170 200
240 280
General Electrical Specifications
VCC Supply Current
Start Threshold
COMP = 0 V (No Switching)
GATE(H) Switching, COMP Charging
− 9.0
8.0 8.5
Stop Threshold
GATE(H) Not Switching, COMP Discharging
7.0 7.5
Hysteresis
Start − Stop
0.75 1.0
3. Characteristics at temperature extremes are guaranteed via correlation using quality statistical control methods.
4. Guaranteed by design. Not tested in production.
Max
80
80
105
105
−
−
0.5
115
0.525
−
75
300
1.4
230
320
12
9.0
8.0
1.25
Unit
ns
ns
ns
ns
ns
V
V
kW
V
%
mV
ns
V
kHz
kHz
mA
V
V
V
http://onsemi.com
5
5 Page 
NCP1575
8.5 V
0.465 V
VIN
VCOMP
VFB
GATE(H)
UVLO STARTUP
tS NORMAL OPERATION
Figure 21. Idealized Waveforms
Normal Operation
During normal operation, the duty cycle of the gate drivers
remains approximately constant as the V2 control loop
maintains the regulated output voltage under steady state
conditions. Variations in supply line or output load conditions
will result in changes in duty cycle to maintain regulation.
Input Supplies
The NCP1575 can be used in applications where a 12 V
supply is available along with a lower voltage supply. Often
the lower voltage supply is 5 V, but it can be any voltage less
than the 12 V supply minus the required gate drive voltage
of the top MOSFET. The greater the difference between the
two voltages, the better the efficiency due to increasing VGS
available to turn on the upper MOSFET. In order to maintain
power supply stability, the lower supply voltage should be
at least 1.5 times the desired voltage.
Adding a few additional components allows the NCP1575
to convert power in a “12 V only” application. This circuit
is illustrated in Figure 1. Note that in all cases, the maximum
supply voltage specification of 20 V must not be exceeded.
Gate Charge Effect on Switching Times
When using the onboard gate drivers, the gate charge has
an important effect on the switching times of the FETs. A
finite amount of time is required to charge the effective
capacitor seen at the gate of the FET. Therefore, the rise and
fall times rise linearly with increased capacitive loading.
Transient Response
The 200 ns reaction time of the control loop provides fast
transient response to any variations in input voltage and
output current. Pulse−by−pulse adjustment of duty cycle is
provided to quickly ramp the inductor current to the required
level. Since the inductor current cannot be changed
instantaneously, regulation is maintained by the output
capacitors during the time required to slew the inductor
current. For better transient response, several high
frequency and bulk output capacitors are usually used.
Overvoltage Protection
Overvoltage protection is provided as a result of the
normal operation of the V2 control method and requires no
additional external components. The control loop responds
to an overvoltage condition within 200 ns, turning off the
upper MOSFET and disconnecting the regulator from its
input voltage. This results in a crowbar action to clamp the
output voltage, preventing damage to the load. The regulator
remains in this state until the overvoltage condition ceases.
Shutdown
When the input voltage connected to VCC falls through the
lower threshold of the UVLO comparator, a fault latch is set.
The fault latch provides a signal that forces both GATE(H)
low and GATE(L) high, producing a low−impedance current
sink to ground at the converter switch node. At the same
time, the latch also turns on a transistor which pulls down on
the COMP pin, quickly discharging the external capacitor,
and allowing COMP to fall.
CONVERTER DESIGN
Choosing the VOUT Resistor Divider Values
The NCP1575 has an internal 0.98 V reference. A resistor
divider is used to set the output voltage.
VOUT
R1
VFB
R2
Figure 22.
The formula to set the output voltage is
VOUT + (R1ńR2 ) 1) < (0.98 V)
Arbitrarily choose a value of R2 that is sufficiently low
that the VFB bias current (typically 50 nA) will have
negligible effect on the output voltage. Solve the equation
above for the value of R1.
Choosing the Oscillator Frequency
The NCP1575 has an oscillator that is trimmed to 200 kHz
at the factory. The NCP1575 will operate at this frequency
without the addition of any external components. However,
the oscillator is user−programmable with a single resistor.
This resistor is connected between the ROSC pin and ground.
Adding this resistor will raise the frequency above 200 kHz.
A graph of oscillator frequency vs. ROSC resistance is
provided in the typical operating characteristics section of
this data sheet.
Selection of the Output Capacitors
These components must be selected and placed carefully
to yield optimal results. Capacitors should be chosen to
provide acceptable ripple on the regulator output voltage.
Key specifications for output capacitors are their Equivalent
http://onsemi.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet NCP1575.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| NCP1570 | Low Voltage Synchronous Buck Controller | ON Semiconductor |
| NCP1571 | Low Voltage Synchronous Buck Controller | ON Semiconductor |
| NCP1573 | Low Voltage Synchronous Buck Controller | ON Semiconductor |
| NCP1575 | Low Voltage Synchronous Buck Controller | ON Semiconductor |
| 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 |