NCP3011: 400kHz / 9-18V / 5A PWM Controller with Ceramic Output Capacitors

Design Note – DN06075/D
12V Input, 5A DC-DC PWM Buck Controller + FET
w/Ceramic Capacitors on the Output
Device
NCP3011
Application
Test & Medical
Equipment
Input
Voltage
Output
Voltage
Output
Current
Topology
9-18V
1.8V
0.01-5A
Buck
Table 1: Buck Power Supply
Characteristic
Input Voltage
Output Voltage
Output Current
Oscillator Frequency
Output Voltage Ripple
Min
9
.01
350
Circuit Description
Typ
12
1.8
3
400
10
Max
18
5
450
Unit
V
V
A
kHz
mVpk-pk
Key Features
This circuit is proposed for a wide
varying +12V input (9V-18V) where there is a
need to step-down the voltage to +5V @ 5A.
The requirement specified a low output
voltage ripple and all ceramic output
capacitors for low noise environments such
as medical devices and automated test
equipment. Input capacitance can also be
optimized for all ceramic but in this demo
board
configuration
two
electrolytic
capacitors are used. Target efficiency is
>85%.
The PCB for the NCP3011 is a 2-layer
board for use in applications up to 50W. The
synchronous buck converter uses voltage
mode control, which can be compensated
externally with a transconductance amplifier
and type-III compensation which enables
ceramic capacitors on the output. The soft
start time is fixed.
The NCP3011
demonstration board is a flexible design
allowing the use of electrolytic capacitors or
ceramic capacitors. It also allows the use of
SO8-FL or D-PAK MOSFETs.
 High Efficiency
 Adjustable Current Limit
 Output Overvoltage and Output Undervoltage
protection
 Short Circuit Protection
 Fixed Switching Frequency
Rev 0, January 2011
Theory of Operation
One feature of the NCP3011 controller is that when one follows a few simple design rules, the transconductance amplifier can
be employed as a voltage feedback Error Amplifier. Theoretically, a transconductance amplifier is an equivalent voltage
controlled current source. It multiplies the difference of input voltage with a certain gain and generates a current into the
output node. It features high output impedance and it is stable by most of the output compensation components. The goal of
the design is to provide a loop gain function with a high bandwidth (high zero-crossover frequency) and adequate phase
margin. As a result, fast load response and good steady state output can be achieved.
•
•
•
Used when loop bandwidth is beyond the LC resonance and ceramic capacitors are used
Rc1 > 2/gm (required)
1/gm > Rf1//Rf2//Rf3 (desired)
•
When conditions met (especially Rc1 > 2/gm), behavior is similar to a voltage amp
Rev 0, January 2011
•
•
•
•
Measured Loop Response
PM = 52 o
f_cross = 24.6 kHz
f0 ~ 3-4 kHz
•
Predicted Loop Response
(utilizing CompCalc design tool: http://www.onsemi.com/pub/Collateral/COMPCALC.ZIP )
PM = 67.9 o
f_cross = 25.1 kHz
f0 ~ 3.4 kHz
•
•
•
Rev 0, January 2011
•
•
•
•
Measured Compensator Response
Max Phase Boost: 128o @15 kHz
fz1/z2 : ~ 2-5 kHz
fp1/p2 : ~ 50-70 kHz
•
Predicted Compensator Response
(utilizing CompCalc design tool: http://www.onsemi.com/pub/Collateral/COMPCALC.ZIP )
Max Phase Boost: 125o @ ~20 kHz
fz1/z2 : ~ 3-5 kHz
fp1/p2 : ~ 200 kHz
•
•
•
Note: CompCalc files with these values pre-loaded are available from the NCP3011 web page under “Design &
Development Tools”
Rev 0, January 2011
Performance
The following figures show typical performance of the NCP3011 demonstration boards.
Efficiency vs Output Current and Input Voltage
100
Efficiency (%)
90
80
Vin = 12 V
70
60
50
40
30
20
0
1
2
3
4
5
Iout (A)
Figure 1: NCP3011 Efficiency at 12V with a 1.8V Output Voltage
Load Regulation vs Input Voltage
1.9
1.89
V-Out (V)
1.88
1.87
1.86
NCP3011
Vin = 11 ‐ 14 V
Vout = 1.87 V
1.85
1.84
0
0.5
1
Vin = 11 V
1.5
2
I-Out (A)
Vin = 12 V
2.5
3
Vin = 13 V
3.5
Vin = 14 V
Figure 2: NCP3011 Load Regulation
Rev 0, January 2011
4
4.5
5
ON Semiconductor
Schematics
Figure 4: NCP3011 Schematic
Rev 0 - January, 2011
ON Semiconductor
Table 2: NCP3011 BOM (1.8Voutput)
Qty
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Reference Value
C1
470uF
C1A
470uF
C2
22uF 25V
C3
22uF 25V
C4
1uF
C5
0.1uF
C6
1uF
C7
27pF
C8
2.7nF
C9
0.1 uF
C10
1.5 nF
C11
100uF*2
C12
100uF*2
C13
DNP
C14
0.1uF
C15
DNP
C16
DNP
C17
1.8nF
C18
DNP
L1
5.6 uH
Part Number
Description
C4532X7R1E226M
C4532X7R1E226M
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
C3225X5R0J107M
C3225X5R0J107M
Ceramic Chip Capacitor
Ceramic Chip Capacitor
Ceramic Chip Capacitor
Ceramic Chip Capacitor
Ceramic Chip Capacitor
SMT Inductor
PCB DECAL
ECA_12.5
ECA_12.5
2220CAP
2220CAP
1206CAP
1206CAP
1206CAP
0603CAP
0603CAP
0805CAP
0805CAP
1210CAP
1210CAP
ECA_12.5
0805CAP
0805CAP
0805CAP
0603CAP
0603CAP
MSS1260
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
Chip Capacitor
1 Q1
NTMS4873NF HSFET
Dual Use Footprint; SOPFL and DPAK MOSFET
COMBO2_SO8FL-DPAK
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
NTMS4873NF
13.3k
10k
22.1k
499
DNP
12k
0R0
0R0
10k
1.18
0R0
22.1k
0R0
0R0
DNP
22.1k
DNP
20R
28 V 400 kHz
DNP
BAT54T1G
Dual Use Footprint; SOPFL and DPAK MOSFET
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
Resistor
SMT Resistor
Resistor
SMT Resistor
Resistor
Resistor
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
SMT Resistor
Synchronous PWM Controller
Schottky Barrier Diodes
Schottky Barrier Diodes
COMBO2_SO8FL-DPAK
0603RES
0603RES
0603RES
0603RES
0603RES
1206RES
0603RES
1206RES
0603RES
1206RES
1206RES
0603RES
0603RES
0603RES
0603RES
0603RES
0603RES
0603RES
TSSOP-14
SOD_123_BAT54T1
SOD_123_BAT54T1
Q2
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
R16
R17
R18
U1
D1
D2
LSFET
CRCW12060000Z0EA
CRCW06030000Z0EA
CRCW12068R06FNEA
CRCW060310K0FKEA
CRCW12060000Z0EA
CRCW060322K1FKEA
CRCW060310K0FKEA
CRCW06030000Z0EA
CRCW0603750RFKEA
CRCW060320R0FKEA
NCP3011
Sync Diode
Rev 0 - January, 2011
ON Semiconductor
Vout
1.0V
1.8V
2.5V
3.3V
5.0V
C7
27pF
68pF
27pF
27pF
27pF
C8
2.7nF
8.2nF
2.7nF
2.7nF
2.7nF
C10
1.5nF
1.5nF
1.5nF
1.5nF
1.5nF
C17
1.8nF
3.9nF
1.8nF
2.7nF
1.8nF
L1
5.6uH
5.6uH
5.6uH
5.6uH
6.8uH
R1
15.8k
9.76k
15.8k
10.5k
15.4k
R2
52.3k
7.32k
7.15k
3.24k
2.87k
R3
22.1k
10k
22.1k
22.1k
22.1k
R4
599
182
499
340
499
R10
1.18
1.18
1.18
1.18
1.18
C11
100uF*2
100uF*2
100uF*2
100uF*3
47uF*3
C12
100uF*2
100uF*2
100uF*2
100uF*2
47uF*3
Table 3: Component Recommendations for Different Output Voltages
© 2011 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor does ON Semiconductor convey any license
to its or any third party’s intellectual property rights. This document is provided only to assist customers in evaluation of the referenced circuit implementation and the
recipient assumes all liability and risk associated with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of
its products at any time, without notice.
Design note created by Tim Kaske and Jim Hill, e-mail: [email protected] ; [email protected]
Rev 0 - January, 2011