an1539

Application Note 1539
ISL8112EVAL1Z Evaluation Board Setup Procedure
The ISL8112 is a dual-output Synchronous Buck
controller with 2A integrated driver. It features high
light load efficiency which is especially preferred in
systems concerned with high efficiency in wide load
range, like the battery powered system. ISL8112
includes two constant on-time PWM controllers. Both
outputs can operate in an output fixed mode or an
adjustable mode. In fixed mode, one output can be 5V
or 3.3V and the other 1.5V or 1.05V. In adjustable
mode, one output can range from 0.7V to 5.5V, and the
other from 0V to 2.5V (sensing output voltage directly)
or up to 5V (using resistor divider voltage for voltage
sensing). This device also features a linear regulator
providing 3.3V/5V, or adjustable from 0.7V to 4.5V via
LDOREF. The linear regulator provides up to 100mA
output current with automatic linear-regulator
bootstrapping to the BYP input. When in switchover, the
LDO output can source up to 200mA. ISL8112 includes
on-board power-up sequencing, the power-good
(PGOOD_) outputs, digital soft-start, and internal
soft-stop output discharge that prevents negative
voltages on shutdown.
Recommended Equipment
ISL8112 is implemented with constant on-time PWM
control scheme which need no sense resistors and
provides 100ns response to load transients while
maintaining a relatively constant switching frequency.
The unique ultrasonic pulse-skipping mode maintains
the switching frequency above 25kHz, eliminating
undesired audible noises in low frequency operation at
light load. Other features include pulse skipping which
maximizes efficiency in light-load applications, and
fixed-frequency PWM mode which reduces RF
interference in sensitive applications.
Evaluating the Other Output Voltage
FIGURE 1. TOP VIEW
February 22, 2010
AN1539.0
1
• 0V to 25V power supply with at least 20A source
current capability, battery, or notebook AC adapter.
• Two electronic loads capable of sinking current up
to 15A.
• Dummy loads for the LDO’s.
• Digital multimeters (DMMs).
• 100MHz quad-trace oscilloscope.
• Signal generator.
Quick Start
1. Ensure that the circuit is correctly connected to the
supply and loads prior to applying any power.
2. Verify that position 2’s are ON for SW1, SW2, SW3,
SW4, and SW5. Make sure that no other position of
each switch is ON at the same time.
3. Turn on the input power supply.
4. Verify the output voltages are correct.
5. Verify the LDOs output voltages are correct.
The ISL8112EVAL1Z board outputs are preset to 5V/7A,
3.3V/7A and 5V/200mA on LDO. The VOUT1 can also be
adjusted between 0.7V to 5.5V by changing the value of
R9 and R10 or R11 and R12 given by Equation 1:
R 11
R 12 = --------------------------------------------( V OUT ⁄ V FB ) – 1
(EQ. 1)
where VFB = 0.7V
• The VOUT2 can track OUT2REF at 1:1 ratio with input
voltage range from 0.7V to 2.5V. Likewise, the LDO
output can also track LDOREF at 1:2 with voltage
range from 0.35V to 2.25V.
FIGURE 2. BOTTOM VIEW
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. 2010. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1539
ISL8112EVAL1Z Board Schematic
P18
VOUT1
VCC
R11
OPEN
C3
1000PF
R12
0
R16
200K
C1
1UF
6
5
PH1
4
C16
10UF
2
D9
IRF7811AV
Q4
1
7
6
4
5
D5
C17
1000PF
1
MODE
P15
1
PGOOD1
P24
2
D1
1
C23
0.1UF
1
2 P23
4
5V
1
P17
VOUT2
61
5
VOUT1
4
3
1
PVCC
R34
OPEN
1
EN_LDO
P27
1
1
1
2
3
1
P8
D7
BAT54S
C5
0.1UF
2
BYP
P28
R6
25.5
D8
BAT54S
NC
PGOOD2
C30
C32
330UF 330UF
C12
0.1UF
SW4
1
2
3
P16
EN1
1
C28
DNP
R26
DNP
P7
VOUT1
8
3
C2
0.1UF
SW3
1
2
3
1
2
3
P12
EN2
2
L1
4.7UH
VCC
6
5
4
6
5
4
6
5
4
1
2
3
0
P11
1
2 P21
1
6
5
4
R4
200K
R17
2
1
3
3
4
1
R23
OPEN
R5
200K
4
P6
7
C6
0.1UF
R14
OPEN
SW5
3.3V
1
2 P22
1
VIN
8
2
FS
3
1
Q3
2
P30
SW2
C24
0.1UF
2
3
R8
1
VREF1
SW1
1
1
2
1
D2
IRF7807V
1
R2
OPEN
FB1
R20
OPEN
C8
1UF
1
VOUT1
C31
330UF
3
LDO
R24
0
R19
OPEN
R3
0
VCCIN
PVCC
1
C29
330UF
1
R18
OPEN
C27
DNP
R25
DNP
D4
D6 1
R27
OPEN
P29
5
2
VIN
6
4
2
R7
OPEN
1
C15
1000PF
7
3
NC
PVCC
P5
1
1
P26
EP
1
VOUT2
2
1
P2
R31
0
C19
OPEN
ISL8112
Q2
2
R1
1
8
1
2 P20
P4
3
C7
1UF
1
2
P3
1
4
3
LDO
5
1
1
4
PH2
P19 4
C14
10UF
IRF7811AV
BOOT2
LG2
PGND
GND
NC
PVCC
LG1
BOOT1
U1
0.1UF
D3
BYP
VSEN1
FB1
ILIM1
PGOOD1
EN1
UG1
PH1
VIN
1
P1
VREF1
FS
VCC
EN_LDO
VREF2
VIN
LDO
LDOREF
FS
VCC
EN_LDO
P14
VREF2
BYP
R30
0
6
1
C10
PVCC
3
C9
0.01UF
7
3
C26
0.1UF
L2
OUT2REF
ILIM2
VSEN2
MODE
PGOOD2
EN2
UG2
PH2
C4
0.1UF
VCC
LDO
C11
4.7UF
1
VREF1
R13
OPEN
VIN
8
Q1
2
VCC
3
C18
OPEN
PGOOD1
EN1
R10
0
1
R15
200K
VOUT2
MODE
PGOOD2
EN2
R9
OPEN
VREF2
IRF7807V
2
R21
0
3
1
R22
OPEN
R33
200K
C13
R32
39.2K
0.1UF
FIGURE 3. ISL8112EVAL1Z REV A BOARD SCHEMATIC
TABLE 1.
SW1
EN2
VOUT2 OUTPUT CONTROL
1
Connect to GND.
VOUT2 output shutdown.
2
Connect to VCC.
VOUT2 output active.
3
Connect to VREF1.
VOUT2 sequence to VOUT1 output.
NOTE: Only toggle one position at a time.
TABLE 2.
SW2
MODE
OPERATING MODE
1
Connect to GND.
Normal operation mode, allow automatic PWM/PFM switchover for
pulse-skipping at light load.
2
Connect to VCC.
Low noise, fixed-frequency PWM mode.
3
Connect to VREF1.
Ultrasonic pulse-skipping mode (20kHz min.)
NOTE: Only toggle one position at a time.
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AN1539.0
February 22, 2010
Application Note 1539
TABLE 3.
SW3
EN_LDO
LDO CONTROL
1
Connect to GND.
LDO output shutdown.
2
Connect to VCC.
LDO output active.
3
N/C
No Connect.
NOTE: Only toggle one position at a time.
TABLE 4.
SW4
BYP
OPERATING MODE
1
Connect to GND.
Set BYP to 0V. No LDO switchover.
2
Connect to VOUT1.
SET BYP to VOUT1.
3
Connect to VOUT2.
SET BYP to VOUT2.
NOTE: Only toggle one position at a time.
TABLE 5.
SW5
EN1
VOUT1 OUTPUT CONTROL
1
Connect to GND.
VOUT1 output shutdown.
2
Connect to VCC.
VOUT1 output active.
3
Connect to VREF1.
VOUT1 sequence to VOUT2 output.
NOTE: Only toggle one position at a time.
Components List
REF DES
C1, C7, C8
C11
C14, C16
PART NUMBER
QTY
MANUFACTURER
DESCRIPTION
08053D105KAT2A
3
AVX
1µF, 25V, X7R, 0805
H1065-00475-10V10
1
GENERIC
4.7µF, 10V X5R 1206
TMK432BJ106KM
2
TAIYO-YUDEN
10µF, 25V X5R 1210
GENERIC
0.1µF, 50V, X7R, 0805
C2, C4, C5, C6, C10,
H1046-00104-50V10
C12, C13, C23, C24, C26
10
C27, C28
OPEN
0
-
-
C29, C30
6TPD330M
2
POSCAP SANYO
330µF, 6.3V, POS CAP 9mΩ, D size
-
-
C3, C9, C15, C17, C18,
C19
OPEN
C31, C32
OPEN
0
POSCAP
-
D1, D4-D6
OPEN
0
DIODES-INC
-
D2, D3
OPEN
0
ON-SEMI
-
D7, D8
OPEN
0
DIODES
-
D9
OPEN
0
ON-SEMI
0.3A, 30V, Schottky SOT23
DR125-4R7-R
2
COOPER/COILTRONICS 4.7µH, 10.5mΩ, 12.5x12.5mm Shielded
1514-2
6
KEYSTONE
Test Point Turret 0.150 Pad 0.100 Thole
131-4353-00
5
TEKTRONIX
Scope Probe Test Point PCB Mount
KEYSTONE
Miniature Red Test Point 0.100 Pad
0.040 Thole
KEYSTONE
Miniature Black Test Point 0.100 Pad
0.040 Thole
L1, L2
P1, P2, P5-P8
P19-P23
P3, P11, P12, P14-P18,
P24, P26-P29
5000
P4, P30
5001
3
0
13
2
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February 22, 2010
Application Note 1539
Components List
REF DES
(Continued)
PART NUMBER
QTY
MANUFACTURER
DESCRIPTION
Q1
IRF7821
1
IR
30V 13.6A HEXFET Power MOSFET
Q2
IRF7832
1
IR
30V 20A HEXFET Power MOSFET
Q3
IRF7807V
1
IR
30V 8.3A N-Channel Power MOSFET
Q4
IRF7811AV
1
IR
30V 10.8A N-Channel Power MOSFET
R1, R8
H2512-01R00-1/10W
2
GENERIC
1Ω, 1%, 0805
R15
H2512-01503-1/10W1
1
GENERIC
150kΩ, 1%, 0805
-
-
-
-
GENERIC
0Ω, 1%, 0805
R2, R7, R9, R11, R13,
R14, R18, R19, R20,
R22, R23, R27, R34
OPEN
R25, R26
OPEN
0
0
R3, R10, R12, R17,
R21, R24, R30, R31
H2512-00R00-1/10W
R32
H2512-03922-1/10W1
1
GENERIC
39.2kΩ, 1%, 0805
R4, R5, R16, R33
H2512-02003-1/10W1
4
GENERIC
200kΩ, 1%, 0805
R6
H2512-025R5-1/10W1
1
GENERIC
25.5Ω, 1%, 0805
78B03S
5
GRAYHILL
Dip Switch SPST (Raised Slide)
ISL8112IRZ
1
INTERSIL
High-Efficiency, Quad Output Controller
SW1-SW5
U1
8
Layout
FIGURE 4. TOP COMPONENTS
4
FIGURE 5. TOP ETCH
AN1539.0
February 22, 2010
Application Note 1539
Layout
(Continued)
FIGURE 6. 2nd LAYER
FIGURE 7. 3rd LAYER
FIGURE 8. BOTTOM COMPONENTS (MIRRORED)
FIGURE 9. BOTTOM ETCH
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
5
AN1539.0
February 22, 2010
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