an1919

Application Note 1919
ISL8115DEMO1Z Synchronous Buck Converter User
Guide
Introduction
Key Features
The ISL8115DEMO1Z is a compact reference design
Synchronous Buck Converter (28.19mmx16.89mm)
implementing Intersil’s wide input range PWM controller
ISL8115. Utilizing voltage mode control with input
feed-forward, the ISL8115DEMO1Z maintains a constant loop
gain for optimal transient response, especially for applications
with a wide input voltage range. For a more detailed
description of the ISL8115 functionality, refer to the ISL8115
datasheet.
• Small, compact design
This user guide includes the test setup, typical performance
waveforms, schematic, layout and bill of materials (BOM).
DESCRIPTION
Input voltage range
MIN
TYP
16
24
MAX UNIT
36
V
VOUT
Output voltage
5
V
IOUT
Output rated current
10
A
IOC
Overcurrent threshold
13
A
fsw
Switching frequency
600
kHz
15
V
Falling threshold
14.2
V
Efficiency at 24V input full
load (10A)
90.12
%
Input UVP Rising threshold
η
• Oscillator programmable from 150kHz to 1.5MHz
- Frequency synchronization to external clock signal
• Output OVP/UVP; OCP and OTP
TABLE 1. DEMONSTRATION BOARD ELECTRICAL SPECIFICATIONS
VIN
• Integrated 5V high speed 4A MOSFET gate drivers
- Internal bootstrap diode
• Diode emulation mode for light load efficiency improvement
Specifications
SPEC
• Fast transient response
- Voltage-mode PWM leading-edge modulation with
nonlinear control
- Input voltage feed-forward
• Adjustable soft-start
• Prebias start-up function
• Excellent output voltage regulation
- 0.6V ±1.0% internal reference (-40°C~+125°C)
- 0.6V ±0.7% internal reference (-40°C~+105°C)
- Differential voltage sensing
References
• ISL8115 datasheet
Ordering Information
PART NUMBER
ISL8115DEMO1Z
DESCRIPTION
Demonstration Board for ISL8115
Recommended Equipment
• Input power source up to 36V supply voltage with 125W
power supply ability
• Electronic load with 100W power sinking ability
• Voltmeters and ammeters
• 100MHz quad-trace oscilloscope
FIGURE 1. ISL8115DEMO1Z DEMONSTRATION BOARD
March 11, 2015
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2014, 2015. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
Application Note 1919
FIGURE 2. ISL8115DEMO1Z TEST SETUP
Quick Test Setup
1. Ensure that the demonstration board is correctly connected to
the power supply and the electronic load prior to applying any
power. Refer to Figure 2 for proper setup.
2. Set the input voltage to 24V, turn on the power supply and
observe output voltage. The output voltage variation should
be within 5%.
3. Adjust load current within 10A. The output voltage variation
should be within 5%.
4. Use oscilloscope to observe output ripple voltage and phase
node ringing. For accurate measurement, refer to Figure 3 for
proper setup.
Probe Setup
Design Guide
The ISL8115DEMO1Z is optimized for 16V to 36V input voltage
range. However, the evaluation board can be modified to support
multiple applications due to the customer’s requirements. Refer
to the ISL8115 datasheet for detailed information.
TABLE 2. 12V APPLICATION
VIN
R35
12V
71.5k
Quick modify to 12V input application, Table 2 can be followed.
Some other modifications need to be made at the same time if
best performance is expected.
Output Voltage Adjustment
The output voltage can be set by the resistors R4 and R1. In order
to keep the existing compensation parameters unchanged,
adjust R4 to set the output voltage by the following Equation 1:
0.6V  R 1
R 4 = ---------------------------------V OUT – 0.6V
(EQ. 1)
The VMON monitors the output for UVP and OVP, the resistor
divider value of R11/R8 should be the same with the R1/R4.
Synchronization
FIGURE 3. OSCILLOSCOPE PROBE SETUP
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2
The ISL8115DEMOZ board can be synchronized with an external
clock. Applying a clock signal (10% to 90% duty cycle) in the
range of 150kHz to 1.5MHz to the FSET pin makes the internal
frequency synchronized with the external clock. Please remove
R27 when the synchronized function is implemented.
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Application Note 1919
Typical Performance Curves
Unless otherwise specified, the input voltage is 28V.
95
95
85
90
EFFICIENCY (%)
EFFICIENCY (%)
75
85
VIN = 16V
80
75
VIN = 36V
VIN = 24V
65
VIN = 16V
55
VIN = 36V
45
VIN = 24V
35
25
70
65
15
1
2
3
4
5
6
7
8
9
5
10
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
4.0
3.6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
FIGURE 5. EFFICIENCY vs LOAD CURRENT AT DEM MODE
FIGURE 4. EFFICIENCY vs LOAD CURRENT AT CCM MODE
5.0390
5.0370
5.0365
5.0380
5.0370
5.0355
VOUT (V)
VOUT (V)
5.0360
5.0350
5.0345
5.0360
5.0350
VIN = 24V
VIN = 24V
5.0340
5.0340
5.0335
5.0330
0
1
2
3
4
5
6
LOAD CURRENT (A)
7
8
9
5.0330
10
FIGURE 6. VOUT LOAD REGULATION AT CCM MODE
2
3
4
5
6
LOAD CURRENT (A)
7
8
9
10
5.038
5.038
5.037
5.037
5.036
5.037
5.036
VOUT (V)
VOUT (V)
1
FIGURE 7. VOUT LOAD REGULATION AT DEM MODE
5.038
5.036
5.035
0
NO LOAD
5.035
5.034
5.033
5.035
5.032
5.034
NO LOAD
5.034
5.031
5.033
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
VIN (V)
5.030
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
VIN (V)
FIGURE 8. LINE REGULATION AT NO LOAD CCM MODE
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FIGURE 9. LINE REGULATION AT NO LOAD DEM MODE
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Application Note 1919
Typical Performance Curves
Unless otherwise specified, the input voltage is 28V. (Continued)
5.038
5.037
5.037
5.036
5.035
VOUT (V)
VOUT (V)
5.036
5.035
5.034
FULL LOAD 10A
5.033
5.033
FULL LOAD 10A
5.032
5.031
5.032
5.031
16
5.034
5.030
18
20
22
24
26
28
VIN (V)
30
32
34
5.029
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
VIN (V)
36
FIGURE 10. LINE REGULATION AT FULL LOAD CCM MODE
FIGURE 11. LINE REGULATION AT FULL LOAD DEM MODE
VOUT
OUTPUT LOAD
20mV/DIV
5A/DIV
10µs/DIV
FIGURE 12. OUTPUT VOLTAGE RIPPLE AT 10A LOAD CONDITION
VOUT
100mV/DIV
OUTPUT LOAD
5A/DIV
VOUT
100mV/DIV
OUTPUT LOAD
5A/DIV
100µs/DIV
100µs/DIV
FIGURE 13. LOAD TRANSIENT 0A TO 5A; 2A/µs AT CCM
FIGURE 14. LOAD TRANSIENT 5A TO 10A; 2A/µs AT CCM
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Application Note 1919
Typical Performance Curves
VOUT
2V/DIV
OUTPUT LOAD
5A/DIV
Unless otherwise specified, the input voltage is 28V. (Continued)
VOUT
2V/DIV
OUTPUT LOAD 5A/DIV
2msDIV
2ms/DIV
FIGURE 15. START-UP AT 0A LOAD CONDITION
FIGURE 16. START-UP AT 10A LOAD CONDITION
VOUT
OUTPUT LOAD
2V/DIV
5A/DIV
VOUT
VOUT
500mV/DIV
OUTPUT LOAD
5A/DIV
500µs/DIV
FIGURE 18. SHUTDOWN AT 10A LOAD CONDITION
VOUT
OUTPUT LOAD
PH
PH
1V/DIV
5A/DIV
50V/DIV
20V/DIV
5ms/DIV
FIGURE 19. OVERCURRENT PROTECTION AT 12.6A LOAD
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5A/DIV
OUTPUT LOAD
100µs/DIV
FIGURE 17. SHUTDOWN AT 0A LOAD CONDITION
2V/DIV
5
5ms/DIV
FIGURE 20. SHORT PROTECTION
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R4
R8
2K
2K
R1
14.7k
C3
R3
1. 8n
R 11
14.7k
R9
0
133
C17
47nF
C1
20
R23
22
ISHARE
PVCC
U1
PLL_COMP
PHASE
ISL8115
CONF
UG ATE
BOOT
L1
2.4uH
TP3
2
8
Q2
C16
1
VOUT
VOUT
74432524 0
2.4uH 14 A 4.8mohm
C36
DNP
0.22uF
7
C24
C26
100uF
100uF
C23
C25
100uF
100uF
C11
1uF
5V/10A
C 15
1uF
TP4
VFF
1
R14
2
R27
C21
2.2uF
GND
Upper MOS: BSC039N06NS
Lower MOS: BSC039N06NS
R20
R36
46. 4K
input rising shreshold: 15V
input falling shreshold: 14.2V
1
4
9
40. 2K
R29
10k
4.7uF
10
6
RAMP
EN
VIN
5
4
3
2
VCC
SS
PGOOD
CLKOUT
1
18.2K
24
F SET
23
Q4
C 20
11 PVCC
732
R26
1
2
3
13
ISEN A
14
ISENB
15
16
LG ATE
R28
9.1k
C22
2. 2uF
R35
113k
30K
R12
2k
R34
2.2
TP1
PVCC
1
VIN
C30
10uF
DEMO1Z
Input: 16V - 36V
Frequency: 600KHz
C29
10uF
C35
100uF
16 - 3 6V
Output: 5V/10A
TP2
1
GND
FIGURE 21. ISL8115DEMO1Z SCHEMATIC
Application Note 1919
21
ISET
4
12
5
390pF
VMON
19
R39
10k
1
2
3
5.11K
C19
GND
RGND
R21
17
470p
4.22k
FB
C4
25
R17
C2
33p
18
R40
10k
R2
16.5k
COMP
6
C14
2.2nF
R22
0
2.2nF
Average OCP: 12.8A
Peak current limit: 13A
5
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Schematic
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Application Note 1919
Bill of Materials
ITEM
QTY
REFERENCE
VALUE
DESCRIPTION
1
2
C1, C14
2.2nF
CAP CER 2200pF 25V 10% X7R 0402
Generic
Generic
2
1
C2
33pF
CAP CER 33pF 50V 5% NP0 0402
Generic
Generic
3
1
C3
1.8nF
CAP CER 1800pF 50V 10% X7R 0402
Generic
Generic
4
1
C4
470pF
CAP CER 470pF 50V 10% X7R 0402
Generic
Generic
5
2
C11, C15
1µF
CAP CER 1µF 10V 10% X5R 0603
Generic
Generic
7
1
C16
0.22µF
CAP CER 0.22µF 16V 10% X7R 0402
Generic
Generic
8
1
C17
47nF
CAP CER 0.047µF 25V 10% X7R 0402
Generic
Generic
9
1
C19
390pF
CAP CER 390pF 50V 10% X7R 0402
Generic
Generic
10
1
C20
4.7µF
CAP CER 4.7µF 6.3V 10% X5R 0805
Generic
Generic
11
1
C21
2.2µF
CAP CER 2.2µF 50V 10% X7R 1210
TDK
12
1
C22
2.2µF
CAP CER 2.2µF 6.3V 20% X5R 0603
Generic
13
4
C23, C24, C25,
C26
100µF
CAP CER 100µF 6.3V 20% X5R 1210
TDK
C3225X5R0J107M250AC
14
2
C29, C30
10µF
CAP CER 10µF 50V 10% X5R 1206
TDK
C3216X5R1H106K160AB
15
1
C35
100µF
CAP ALUM 100µF 50V 20% SMD
16
1
C36
DNP
17
1
L1
2.4µH
18
2
Q2, Q4
BSC039N06NS
19
2
R1, R11
20
1
21
CAP 220µF 6.3V
INDUCTOR POWER 2.4µH 31.5A SMD
MANUFACTURER
Nichicon
Panasonic
WE-Midcom
PART NUMBER
C3225X7R1H225K
Generic
PCV1H101MCL2GS
6TPF220M5L
744325240
MOSFET N-CH 60V 19A TDSON-8
Infineon
BSC039N06NS
14.7k
RES 14.7kΩ 1/16W 1% 0402 SMD
Generic
Generic
R2
16.5k
RES 16.5kΩ 1/16W 1% 0402 SMD
Generic
Generic
1
R3
133
RES 133Ω 1/16W 1% 0402 SMD
Generic
Generic
22
3
R4, R8, R12
2k
RES 2.00kΩ 1/16W 1% 0402 SMD
Generic
Generic
23
2
R9, R22
0
RES 0.0Ω 1/16W JUMP 0402 SMD
Generic
Generic
24
1
R14
2
RES 2.00Ω 1/4W 1% 1206 SMD
Generic
Generic
25
1
R17
4.22k
RES 4.22kΩ 1/16W 1% 0402 SMD
Generic
Generic
26
1
R20
30k
RES 30kΩ 1/16W 1% 0402 SMD
Generic
Generic
27
1
R21
5.11k
RES 5.11kΩ 1/16W 1% 0402 SMD
Generic
Generic
28
1
R23
732
RES 732Ω 1/16W 1% 0402 SMD
Generic
Generic
29
1
R26
18.2k
RES 18.2kΩ 1/16W 1% 0402 SMD
Generic
Generic
30
1
R27
40.2k
RES 40.2kΩ 1/16W 1% 0402 SMD
Generic
Generic
31
1
R28
9.1k
RES 9.1kΩ 1/16W 1% 0402 SMD
Generic
Generic
32
3
R29, R39, R40
10k
RES 10kΩ 1/16W 1% 0402 SMD
Generic
Generic
33
1
R34
2.2
RES 2.2Ω 1/16W 1% 0402 SMD
Generic
Generic
34
1
R35
113k
RES 113kΩ 1/16W 1% 0402 SMD
Generic
Generic
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Application Note 1919
Assembly Drawing
FIGURE 22. TOP
FIGURE 23. BOTTOM
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Application Note 1919
PCB Layout
FIGURE 24. TOP LAYER
FIGURE 25. LAYER 2
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Application Note 1919
PCB Layout (Continued)
FIGURE 26. LAYER 3
FIGURE 27. BOTTOM LAYER
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is
cautioned to verify that the document is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
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