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Número de pieza | NCP1587A | |
Descripción | Low Voltage Synchronous Buck Controller | |
Fabricantes | ON Semiconductor | |
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No Preview Available ! NCP1587, NCP1587A
Low Voltage Synchronous
Buck Controller
The NCP1587 and NCP1587A are low cost PWM controllers
designed to operate from a 5 V or 12 V supply. These devices are
capable of producing an output voltage as low as 0.8 V. These 8−pin
devices provide an optimal level of integration to reduce size and cost
of the power supply. The NCP1587/A provide a 1 A gate driver design
and an internally set 275 kHz (NCP1587) and 200 kHz (NCP1587A)
oscillator. In addition to the 1 A gate drive capability, other efficiency
enhancing features of the gate driver include adaptive non−overlap
circuitry. The devices also incorporate an externally compensated
error amplifier and a capacitor programmable soft−start function.
Protection features include programmable short circuit protection and
under voltage lockout (UVLO). The NCP1587/A comes in an 8−pin
SOIC package.
Features
• Input Voltage Range from 4.5 to 13.2 V
• 275 kHz (NCP1587) and 200 kHz (NCP1587A) Internal Oscillator
• Boost Pin Operates to 30 V
• Voltage Mode PWM Control
• 0.8 V ±1.0 % Internal Reference Voltage
• Adjustable Output Voltage
• Capacitor Programmable Soft−Start
• Internal 1 A Gate Drivers
• 80% Max Duty Cycle
• Input Under Voltage Lockout
• Programmable Current Limit
• This is a Pb−Free Device
Applications
• Graphics Cards
• Desktop Computers
• Servers / Networking
• DSP & FPGA Power Supply
• DC−DC Regulator Modules
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MARKING DIAGRAM
8
1
8
SOIC−8
1587x
D SUFFIX
CASE 751
ALYW
G
1
1587x = Specific Device Code
(x = A for NCP1587A,
blank for NCP1587)
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Device
PIN CONNECTIONS
BST 1
TG 2
GND 3
BG 4
8 PHASE
7 COMP/DIS
6 FB
5 VCC
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP1587DR2G SOIC−8 2500/Tape & Reel
(Pb−Free)
NCP1587ADR2G SOIC−8 2500/Tape & Reel
(Pb−Free)
†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, 2009
February, 2009 − Rev. 2
1
Publication Order Number:
NCP1587/D
1 page NCP1587, NCP1587A
TYPICAL CHARACTERISTICS (TA = 25°C unless otherwise noted)
5.0 203
4.7 202
4.4 201
4.1 200 VCC = 12 V
3.8 199 VCC = 5 V
3.5
0
14
10 20 30 40 50 60
TJ, JUNCTION TEMPERATURE (°C)
Figure 3. ICC vs. Temperature
70
198
0
375
10 20 30 40 50 60
TJ, JUNCTION TEMPERATURE (°C)
Figure 4. Oscillator Frequency (FSW) vs.
Temperature
70
13 365
12
355
11
345
10
9 335
8
0 10 20 30 40 50 60
TJ, JUNCTION TEMPERATURE (°C)
Figure 5. Soft Start Sourcing Current vs.
Temperature
70
325
0
10 20 30 40 50 60
TJ, JUNCTION TEMPERATURE (°C)
Figure 6. SCP Threshold vs. Temperature
70
808
806
804
802
800
798
796
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794
792
0
10 20 30 40 50 60
TJ, JUNCTION TEMPERATURE (°C)
Figure 7. Reference Voltage (Vref) vs.
Temperature
70
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5
5 Page NCP1587, NCP1587A
Blue curve: Gain-Frequency
Red curve: Gain-Frequency
(Phase margin = 61.417 degree, Gain margin = 9.347 dB)
Figure 13. Closed-loop Voltage Loop-gain of the NCP1587
DESIGN EXAMPLE II: Type III Compensation
(Oscon Cap. with small ESR; Do not place RC, CC, CP)
Switching Frequency
Fsw = 275 KHz
Output Capacitance
RESR = 7 mW/Each
Output Capacitance
Cout = 2×560 mF
Output Inductance
Lout = 1 mH
Input Voltage
Vin = 12 V
Output Voltage
Vout = 1.6 V
Choose the loop gain crossover frequency;
Fco
+
1
5
Fsw + 55 KHz
The corner frequency of the output filter is calculated below;
FLC + 2
p
1
Ǹ1 mH
1120 mF + 4.7 KHz
Check the ESR zero frequency;
FESR + 2
p
1
RESR
FESR + 2
p
1
7 mW
CO
560 mF + 40.6 KHz
Choose CC1 for the soft start
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CC1 + 33 nF
The compensation capacitor (CC1) is related to the loop
gain magnitude, one zero position and the soft start. By
adjusting the value of this compensation capacitor, the
crossover frequency and the soft start time can be adjusted.
Zeros of the compensation network are calculated as follows;
1st zero;
FZ1
+
FLC
10
+
470
Hz
RC1 + 2
p
1
Fz1
CC1
+2
p
1
470 Hz
30 nF + 11.3 kW
RC1 should be much larger than 2/gm in order to get the
stable system with transconductance amplifier. Ù choose
RC1 = 12.1 kW
2nd zero;
Choose R3 for the crossover frequency. R3 should be
much larger than 2/gm for the stable system.
R3 + 10 kW
Fz2 + FLC + 4.7 KHz
C20 + 2
p
1
Fz2
R3
+2
p
1
4.7 KHz
10 kW + 3.4 nF
Choose C20 = 3.3 nF
Poles of the compensation network are calculated as follows;
1st pole;
Choose R4 to cancel the output capacitor ESR zero.
FP1 + FESR + 40.6 KHz
R4 + 2
p
1
FP1
C20
+2
p
1
40.6 kHz
3.3 n + 1.2 kW
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11
11 Page |
Páginas | Total 16 Páginas | |
PDF Descargar | [ Datasheet NCP1587A.PDF ] |
Número de pieza | Descripción | Fabricantes |
NCP1587 | Low Voltage Synchronous Buck Controller | ON Semiconductor |
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