an1452

ISL8106EVAL1Z User Guide
®
Application Note
Introduction
February 16, 2009
AN1452.0
The value of RSEN can then be calculated by Equation 2:
The ISL8106EVAL1Z evaluation board demonstrates the
performances of the ISL8106, synchronous buck PWM
controller with Intersil’s Robust Ripple Regulator (R3)
technology.
The ISL8106 features a 1.5ms digital soft-start and can be
started into a pre-biased output voltage. The PWM switching
frequency can be programmed from 200kHz to 600kHz. The
ISL8106 can be configured to operate in
Forced-Continuous-Conduction-Mode (FCCM) or in
Diode-Emulation-Mode (DEM), which improves light-load
efficiency. An audio filter prevents the PWM switching
frequency from entering the audible spectrum due to
extremely light load while in DEM. Refer to the ISL8106 data
sheet for a more detailed operation by clicking on the
following link.
I P-P
I FL + ---------- • OC SP • r DS ( ON )
2
R SEN = -----------------------------------------------------------------------------I OC
(EQ. 2)
Where:
- RSEN (Ω) is the resistor used to program the
overcurrent setpoint
- IOC is the ISEN threshold current value sourced from the
ISEN pin that will activate the OCP circuit
- IFL is the maximum continuous DC load current
- IP-P is the inductor peak-to-peak ripple current
- OCSP is the desired overcurrent setpoint expressed as
a multiplier relative to IFL
Power and Load Connections
INPUT VOLTAGE
ISL8106EVAL1Z Reference Design
The PVIN post (J1) is connected to the drain of the upper
MOSFET and the VIN pin of the IC. The post (J2) is
connected to PGND.
The ISL8106EVAL1Z design criteria is listed in Table 1.
OUTPUT VOLTAGE LOADING AND MONITORING
http://www.intersil.com/data/fn/fn9283.pdf
Connect the positive and negative leads of an electronic
load to J3 and J4 respectively. Terminal TP4 (PGND) and
TP5 (VOUT) can be used to measure the output voltage.
TABLE 1. ISL8106EVAL1Z DESIGN CRITERIA
PARAMETERS
VALUE
Input Voltage
7V to 25V
Output Voltage
1.8V
Rated Output Current
25A
Switching Frequency
300kHz
Switch Descriptions
TABLE 2. ISL8106EVAL1Z SWITCH DESCRIPTIONS
TOGGLE SWITCHES
FUNCTION
SW1
OFF: Shorts the EN pin to GND (Disable
the controller)
ON: Enable the controller, EN pin is pulled
to VIN and clamped by D1.
SW2
DEM: FCCM pin is pulled to GND to
enable diode-emulation mode
FCCM: FCCM pin is pulled to VCC to
inhibits diode-emulation mode
Setting Switching Frequency
The switching frequency of ISL8106EVAL1Z can be adjusted
through the resistor, R5, that is connected from the FSET pin
to the GND pin. Programming the approximate PWM
switching frequency can be estimated from Equation 1:
1
R FSET = -------------------------------------------------------– 12
60 • F OSC • [ 1 ×10
]
(EQ. 1)
Test-point Descriptions
Setting Overcurrent Protection Threshold
TABLE 3. ISL8106EVAL1Z TEST POINT DESCRIPTIONS
An overcurrent protection fault will occur when the ISEN pin
has measured more than the OCP threshold current IOC
(26µA, typ.), on consecutive PWM pulses, for a period
exceeding 20µs. It does not matter how many PWM pulses
are measured during the 20µs period. If a measurement falls
below IOC before 20µs has elapsed, then the timer is reset
to zero. A short circuit protection fault will occur when the
ISEN pin has measured more than the short-circuit threshold
current ISC, in less than 10µs, on consecutive PWM pulses.
1
TEST POINTS
SIGNALS
TP1
VCC
TP2
PGND
TP3
PGOOD
TP4
PGND
TP5
VOUT
TP6
PVIN
TP6
LX
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2009. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1452
Typical Performance Curves
EN
100
90
VOUT
EFFICIENCY (%)
80
DEM
70
LX
60
50
FCCM
40
30
PGOOD
20
10
0
0.1
1
10
OUTPUT CURRENT (A)
100
FIGURE 1. EFFICIENCY (VIN = 12V, VOUT = 1.8V, Fsw = 300kHz)
FIGURE 2. SOFT-START: 25A LOAD, FCCM = HIGH
VOUT
EN
VOUT
LX
LX
PGOOD
FIGURE 3. PRE-BIASED START-UP (1V PRE-BIASED)
VOUT
FIGURE 4. STEADY STATE: 25A LOAD
VOUT
LX
LX
FIGURE 5. STEADY STATE: NO LOAD (FCCM)
2
FIGURE 6. STEADY STATE: NO LOAD (DEM)
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February 16, 2009
Application Note 1452
Typical Performance Curves (Continued)
VOUT
VOUT
LX
LX
FIGURE 7. STEADY STATE: 1A LOAD (FCCM)
VOUT
FIGURE 8. STEADY STATE: 1A LOAD (DEM)
VOUT
IL
IL
LX
LX
FIGURE 9. LOAD TRANSIENT: 25A TO 0A (CCM)
FIGURE 10. LOAD TRANSIENT: 0A TO 25A (CCM)
VOUT
VOUT
IL
IL
LX
LX
FIGURE 11. LOAD TRANSIENT: 25A TO 0A (DCM-CCM)
3
FIGURE 12. LOAD TRANSIENT: 0A TO 25A (CCM-DCM)
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February 16, 2009
ISL8106EVAL1Z Schematic
VCC
J1
TP6
R11
4.7k
R16
4.7
RED
R3
0
BOOT
TP7
TP5
VOUT
2
2
2
1
C22
0.1uF
1
C30
330uF
C20
0.1uF
1
C28
330uF
R21
DNP
1
TP4
1
2
2
2
2
C26
DNP
J3
OUT
1
C21
0.1uF
C19
0.1uF
C29
330uF
2
C24
DNP
C27
330uF
1
1
C25
DNP
2
C23
DNP
Q4
C8
1000pF
2
1
0.68uH
2
Q2
VO
8
FSET
FB
6
R18
2.2
2
BSOC
9 BSOC
BG
R12
0
R9
1.69k
1
PGND
J4
GND
1
VO
1
1
FSET 7
EP
COMP 5
1
C7
1nF
D1
4.7V Zener
17
COMP
EN
2
R8
10.7K
FB
VIN
11BGATE
10 PGND
1
2
1
1
1
LX
FCCM
EN 4
2
Q3
12 PVCC
BGATE
ISL8106
FCCM 3
SW1
Q1
L1
PVCC
U1
2
1nF
C4
R17
5.9k
C10
0.22uF
1
VCC
TGATE
VCC 2
PGOOD
1
VIN
TG
2
R5
54.9k
R15
0
R22
DNP
2
C5
10nF
R19
C2
2
VREG
1
R1
68pF
C1
10nF
0
2K
R2
1
1
2
15.8k
2
C9
10nF
R4
1K
R20
P1
0
1
GND
Intersil Corporation
1001 Murphy Ranch Rd.
Milpitas, CA, 95035
Size
Title
AN1452.0
February 16, 2009
Rev
B
ISL8106 Application Schematic
Date:
Thursday, November 13, 2008
Sheet
1
of
1
Application Note 1452
VIN 1
1
2
14
BOOT
R14
SW2
10
2
2
0
TGATE
13
2
16
2
4.7uF
PGOOD
R13
C12
0.1uF
C6
15 LX
1
1
2
1
C11
4.7uF
TP1
R6
1K
J2
TP2
2
2
J5
C17
DNP
2
1
R7
4.7
2
1
3
4
1
C15
560uF
C14
3.3uF
VCC
Q5
BSS123LT1
C16
560uF
1
3.3uF
TP3
1
C13
2
D2
GREEN
5365F
1
PVIN
1
R10
4.7k
Application Note 1452
I
ISL8106EVAL1Z Bill of Materials
ID
REFERENCE
QTY
PART NUMBER
PART TYPE
DESCRIPTION
PACKAGE
VENDOR
1
U1
1
ISL8106IRZ
IC, Linear
IC, Single PWM Controller 16Ld QFN
Intersil
2
Q1, Q3
2
BSC059N04LS G
MOSFET, Single
N-Channel, 40V
TDSON-8
Infineon
3
Q2, Q4
2
BSC018N04LS G
MOSFET, Single
N-Channel, 40V
TDSON-8
Infineon
4
Q5
1
BSS123LT1G
MOSFET
N-Channel
SOT-23
On Semi
5
D1
1
BST52C4V7-7-F
Zener Diode
4.7V, 500mW Zener Diode SOD-123
Diode Inc.
6
D2
1
SSL-LXA3025IGC-TR
LED
RED/GREEN SMD LED
SMD
3mmx2.5mm
Lumex
7
L1
1
IHLP-5050FD-01-R68M01
Inductor
0.68µH Power Inductor
SMD
Vishay
CAPACITORS
8
C15, C16
2
EKZE350ELL561MJ25S Capacitor, Alum.
Elec.
560µF, 20%, 35V
RAD 10x25
United Chemi-con
9
C13, C14
2
C3225X7R1H335M
Capacitor, Ceramic,
X7R
3.3µF, 10%, 50V
SM_1210
TDK/Generic
10 C4, C7, C8
3
Capacitor, Ceramic,
X7R
1000pF, 10%, 50V
SM_0603
Generic
11 C1, C5, C9
3
Capacitor, Ceramic,
X7R
0.01µF, 10%, 50V
SM_0603
Generic
12 C12, C19, C20, C21,
C22
5
Capacitor, Ceramic,
X7R
0.1µF, 10%, 50V
SM_0603
Generic
13 C10
1
Capacitor, Ceramic,
X7R
0.22µF, 10%, 25V
SM_0603
Generic
14 C6, C11
2
Capacitor, Ceramic,
X5R
4.7µF, 10%, 6.3V
SM_0603
Generic
15 C27, C28, C29, C30
4
Capacitor, POSCAP 330µF, 20%, 6.3V, 0.009Ω Case D3L
SANYO
16 C2
1
Capacitor, Ceramic,
X5R
68pF, 10%, 50V
SM_0603
Generic
17 C17, C23, C24, C25,
C26
0
6TPF330M9L
Do Not Populate
RESISTORS
18 R1
1
Resistor, Film
2kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
19 R2
1
Resistor, Film
15.8kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
20 R4,R6
1
Resistor, Film
1kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
21 R21, R22
0
22 R5
1
Resistor, Film
54.9kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
23 R7, R16
1
Resistor, Film
4.7Ω, 1%, 1/16W
SM_0603
Panasonic/Generic
24 R8
1
Resistor, Film
10.7kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
25 R3, R12, R13, R15,
R19, R20
6
Resistor, Film
0Ω, 1%, 1/16W
SM_0603
Panasonic/Generic
26 R9
1
Resistor, Film
1.69kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
27 R10, R11
2
Resistor, Film
4.7kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
28 R14
1
Resistor, Film
10Ω, 1%, 1/16W
SM_0603
Panasonic/Generic
29 R17
1
Resistor, Film
5.9kΩ, 1%, 1/16W
SM_0603
Panasonic/Generic
30 R18
1
Resistor, Film
2.2Ω, 1%, 1/16W
SM_0603
Panasonic/Generic
Do Not Populate
5
SM_0603
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February 16, 2009
Application Note 1452
ISL8106EVAL1Z Bill of Materials (Continued)
ID
REFERENCE
QTY
PART NUMBER
PART TYPE
DESCRIPTION
PACKAGE
VENDOR
OTHERS
31 SW1, SW2
2
GT11MSCKE
32 P1
1
Do Not Populate
33 TP1-TP6
6
5002
34 TP7
0
Do Not Populate
35 J1, J2
2
Blinding Post
36 J5
1
1X2 Header
37 J3, J4
2
TEST POINT
vertical, white
KPA8CTP
Toggle Switch
SMD
C&K
PC test jack
PTH
Keystone
Cable Terminal
BERG/FCI
ISL8106EVAL1Z Printed Circuit Board Layers
FIGURE 13. ISL8106EVAL1Z - TOP LAYER (SILKSCREEN)
FIGURE 14. ISL8106EVAL1Z - TOP LAYER (COMPONENT SIDE)
6
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February 16, 2009
Application Note 1452
ISL8106EVAL1Z Printed Circuit Board Layers (Continued)
FIGURE 15. ISL8106EVAL1Z - LAYER 2
FIGURE 16. ISL8106EVAL1Z - LAYER 3
7
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February 16, 2009
Application Note 1452
ISL8106EVAL1Z Printed Circuit Board Layers (Continued)
FIGURE 17. ISL8106EVAL1Z - BOTTOM LAYER (SOLDER SIDE)
FIGURE 18. ISL8106EVAL1Z - BOTTOM LAYER (SILKSCREEN)
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 Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
8
AN1452.0
February 16, 2009
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