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PDF NCP5211 Data sheet ( Hoja de datos )
| Número de pieza | NCP5211 | |
| Descripción | Low Voltage Synchronous Buck Controller | |
| Fabricantes | ON Semiconductor | |
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NCP5211
Low Voltage Synchronous
Buck Controller
The NCP5211 is a low voltage synchronous buck controller. It
contains all required circuitry for a synchronous buck converter using
external N−Channel MOSFETs. High current internal gate drivers are
capable of driving high gate capacitance of low RDS(on) NFETs for
better efficiency. The NCP5211 is in a 14−pin package to allow the
designer added flexibility.
The NCP5211 provides overcurrent protection, undervoltage
lockout, Soft−Start and built in adaptive nonoverlap. The NCP5211
also provides adjustable fixed frequency range of 150 kHz to 750 kHz.
This gives the designer more flexibility to make efficiency and
component size compromises. The NCP5211 will operate over a 4.5 V
to 14 V range using either single or dual input voltage.
Features
• Switching Regulator Controller
♦ N−Channel Synchronous Buck Design
♦ V2 Control Topology
♦ 200 ns Transient Response
♦ Programmable Fixed Frequency of 150 kHz−750 kHz
♦ 1.0 V 1.5% Internal Reference
♦ Lossless Inductor Sensing Overcurrent Protection
♦ Hiccup Mode Short Circuit Protection
♦ Programmable Soft−Start
♦ 40 ns GATE Rise and Fall Times (3.3 nF Load)
♦ 70 ns Adaptive FET Nonoverlap Time
♦ Differential Remote Sense Capability
• System Power Management
♦ 5.0 V or 12 V Operation
♦ Undervoltage Lockout
♦ On/Off Control Through Use of the COMP Pin
• Pb−Free Packages are Available*
http://onsemi.com
MARKING
DIAGRAM
14
SOIC−14
D SUFFIX
CASE 751A
1
NCP5211xG
AWLYWW
NCP5211x = Specific Device Code
A = Assembly Location
WL = Wafer Lot
Y = Year
WW = Work Week
G = Pb−Free Package
PIN CONNECTIONS
1
GATE(H)
BST
LGND
VFFB
VFB
COMP
SGND
PGND
GATE(L)
VC
IS+
IS−
VCC
ROSC
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 2 of this data sheet.
*For additional information on our Pb−Free strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2006
April, 2006 − Rev. 0
1
Publication Order Number:
NCP5211/D
1 page  
NCP5211
ELECTRICAL CHARACTERISTICS (continued) (−40°C < TA < 85°C; −40°C < TJ < 125°C; 4.5 V < VCC, VC < 14 V; 7.0 V < BST <
20 V; CGATE(H) = CGATE(L) = 3.3 nF; ROSC = 51 k; CCOMP = 0.1 mF, unless otherwise specified.) (Note 3)
Characteristic
Test Conditions
Min Typ Max Unit
General Electrical Specifications
VCC Supply Current
BST/VC Supply Current
Start Threshold
COMP = 0 V (no switching)
COMP = 0 V (no switching)
GATE(H) Switching, COMP Charging
− 5.0 8.0 mA
− 2.0 3.0 mA
3.90
4.05 4.20
V
Stop Threshold
GATE(H) Not Switching, COMP Not Charging
3.75
3.90 4.05
V
Hysteresis
Start−Stop
100 150 200 mV
Sense Ground Current
(Note 4)
− 0.15 1.00 mA
3. Guaranteed by design. Not tested in production.
4. Recommended maximum operating voltage between the three grounds is 200 mV.
VFFB
0.5 V
Σ
PWM Comparator
Reset Dominant
RQ
COMP
VFB
SGND
VCC
IS+
IS−
LGND
− Error Amp
+
1.0 V
ART Ramp
OSC
ROSC
Fault
SQ
PWM FF
0.8 V
VSTART
100 % DC
− Comparator
+
UVLO
Comparator
UVLO
Set Dominant
Fault
SQ
60 mV
OC
Comparator
0.25 V
−
+
RQ
5.0 mA
COMP Discharge COMP
Figure 2. Block Diagram
BST
GATE(H)
VC
GATE(L)
PGND
ROSC
http://onsemi.com
5
5 Page 
NCP5211
VFFB Feedback Selection
To take full advantage of the V2 control scheme, a small
amount of output ripple must be fed back to the VFFB pin,
typically 50 mV. For most application, this requirement is
simple to achieve and the VFFB can be connected directly to
the VFB pin. There are some application that have to meet
stringent load transient requirements. One of the key factor
in achieving tight dynamic voltage regulation is low ESR.
Low ESR at the regulator output results in low output
voltage ripple. This situation could result in increase noise
sensitivity and a potential for loop instability. In applications
where the output ripple is not sufficient, the performance of
the NCP5211 can be improved by adding a fixed amount
external ramp compensation to the VFFB pin. Refer to Figure
7, the amount of ramp at the VFFB pin depends on the switch
node Voltage, Feedback Voltage, R1 and C2.
Vramp + (Vsw * VFB) tonń(R1 C2)
where:
Vramp = amount of ramp needed;
Vsw = switch note voltage;
VFB = voltage feedback, 1 V;
ton = switch on−time.
To minimize the lost in efficiency R1 resistance should be
large, typically 100 k or larger. With R1 chosen, C2 can be
determined by the following;
C2 + (Vsw * VFB) tonń(R1 Vramp)
C1 is used as a bypass capacitor and its value should be
equal to or greater than C2.
Vsw
R1
C1
VFFB
C2
R2
1.0 k
VFB
Figure 7. Small RC Filter Providing the Proper Voltage
Ramp at the Beginning of Each On−Time Cycle
Maximum Frequency Operation
The minimum pulse width may limit the maximum
operating frequency. The duty factor, given by the output/input
voltage ratio, multiplied by the period determines the pulse
width during normal operation. This pulse width must be
greater than 200 ns, or duty cycle jitter could become
excessive. For low pulse widths below 300 ns, external slope
compensation should be added to the VFFB pin to increase the
PWM ramp signal and improve stability. 50 mV of added ramp
at the VFFB pin is typically enough.
Current Sense Component Selection
The current limit threshold is set by sensing a 60 mV
voltage differential between the IS+ and IS− pins. Referring
to Figure 8, the time constant of the R2,C1 filter should be
set larger than the L/R1 time constant under worst case
tolerances, to prevent overshoot in the sensed voltage and
tripping the current limit too low. Resistor R3 of value equal
to R2 is added for bias current cancellation. R2 and R3
should not be made too large, to reduce errors from bias
current offsets. For typical L/R time constants, a 0.1 mF
capacitor for C1 will allow R2 to be between 1.0 k and 10 kW.
The current limit without R4 and R5, which are optional, is
given by 60 mV/R1, where R1 is the internal resistance of the
inductor, obtained from the manufacturer. The addition of R5
can be used to decrease the current limit to a value given by:
ILIM + (60 mV * (VOUT R3ń(R3 ) R5))ńR1
where VOUT is the output voltage.
Similiarly, omitting R5 and adding R4 will increase the
current limit to a value given by:
ILIM + 60 mVńR1 (1 ) R2ńR4)
Essentially, R4 or R5 are used to increase or decrease the
inductor voltage drop which corresponds to 60 mV at the IS+
and IS− pins.
IS−
60 mV Trip
R3
R5
IS+
R2
C1
Switching
Node
R4
L1 R1
L
Figure 8. Current Limit
VOUT
Boost Component Selection for Upper FET Gate Drive
The boost (BST) pin provides for application of a higher
voltage to drive the upper FET. This voltage may be provided
by a fixed higher voltage or it may be generated with a boost
capacitor and charging diode, as shown in Figure 10. The
voltage in the boost configuration would be the summation of
the voltage from the charging diode and the output voltage
swing. Care must be taken to keep the peak voltage with
respect to ground less than 20 V peak. The capacitor should be
large enough to drive the capacitance of the top FET.
http://onsemi.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet NCP5211.PDF ] | |
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