an1806

Application Note 1806
ISL8025xEVAL3Z Evaluation Board User Guide
Description
Key Features
The ISL8025 and ISL8025A evaluation board kits are intended
for use by customers with requirements for Point-of-Load
applications sourcing from 2.7V to 5.5V. The ISL8025 and
ISL8025A evaluation boards are used to demonstrate the
performance of the ISL8025 and ISL8025A, low quiescent high
efficiency synchronous buck regulator.
• High efficiency synchronous buck regulator with up to 95%
efficiency
The ISL8025 and ISL8025A are offered in a 3mmx3mm
16 Ld TQFN package with 1mm maximum height. The
complete area that the converter occupies can be as small as
0.22in2.
• Soft-stop output discharge during disabled
Specifications
PART
NUMBER
IOUT
(MAX)
(A)
ISL8025
ISL8025A
5
• 0.8% reference accuracy over temperature load line
• Start-up with pre biased output
• Internal soft-start - 1ms or adjustable
• Adjustable frequency from 500kHz to 4MHz - default at 1MHz
(2MHz for ISL8025A)
• External synchronization up to 4MHz
• Negative OC protection
FSW RANGE
(MHz)
Programmable
0.5 to 4MHz
Programmable
1 to 4MHz
VIN
VOUT
RANGE RANGE
(V)
(V)
2.7V to
5.5V
0.6V to
5.5V
PART SIZE
(2mm)
3x3
References
ISL8025 Datasheet
Ordering Information
PART NUMBER
NOTES:
1. The Evaluation Kits default configuration are VOUT = 1.8V for
ISL8025EVAL3Z (fSW = 1MHz) and ISL8025AEVAL3Z (fSW = 2MHz).
DESCRIPTION
ISL8025EVAL3Z
Evaluation Board For ISL8025
ISL8025AEVAL3Z
Evaluation Board For ISL8025A
2. VREF is 0.6V.
FIGURE 1. ISL8025EVAL3Z
November 10, 2014
AN1806.2
1
FIGURE 2. ISL8025AEVAL3Z
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1806
Recommended Equipment
Soft-start Control
• 0V to 10V power supply with at least 10A source current
capability or 5V battery
Short CSS to SGND for internal soft-start (approximately 1ms).
Populate CSS to adjust the soft-start time. This capacitor, along
with an internal 1.6µA current source, sets the soft-start interval
of the converter, tSS.
• Electronic loads capable of sinking current up to 7A
CSS  F  = 3.33  t SS  s 
The following materials are recommended to perform testing:
• Digital Multimeters (DMMs)
(EQ. 3)
CSS must be less than 33nF to insure proper soft-start reset after
fault condition.
• 100MHz quad-trace oscilloscope
• Signal generator
Switches Control
Quick Setup Guide
1. Ensure that the circuit is correctly connected to the supply and
loads prior to applying any power.
2. Connect the bias supply to VIN, the plus terminal to VIN, P4
and the negative return to PGND, P5.
The ISL8025, ISL8025A evaluation boards contain SW1 and
SW2 for various controls of the ISL8025, ISL8025A circuitries.
Table 1 details this function.
TABLE 1. SWITCH SETTINGS
SW1
ENABLE
3. Connect the output load to VOUT, the plus terminal to VO, P3
and the negative return to PGND, P7.
FUNCTION
1
OFF
DISABLE VO
4. Verify that the position is PWM for SW2.
3
ON
ENABLE VO
SW2
MODE
1
PWM
Fixed PWM frequency at light
load
3
PFM
Force continuous mode
5. Verify that the position is ON for SW1.
6. Turn on the power supply.
7. Verify the output voltage is 1.8V for VOUT.
Evaluating the Other Output Voltage
The ISL8025 and ISL8025A evaluation board kits output are
preset to 1.8V for VOUT, however, output voltages can be adjusted
from 0.6V to 5V. The output voltage programming resistor, R1,
will depend on the desired output voltage of the regulator. The
value for the feedback resistor is typically between 0Ω and
200kΩ, as shown in Equation 1.
VFB
R 2 = R 1  ---------------------------
 VO – VFB
(EQ. 1)
If the output voltage desired is 0.6V, then R2 is left unpopulated
and R1 is shorted. For faster response performance, add 10pF to
47pF in parallel to R1. Check bode plot to insure optimum
performance.
Frequency Control
The ISL8025 and ISL8025A have an FS pin that controls the
frequency of operation. Programmable frequency allows for
optimization between efficiency and external component size.
Default switching frequency is 1MHz for ISL8025EVAL3Z and
2MHz for ISL8025AEVAL3Z when FS is tied to VIN (R11 = 0 and
R12 is open). By changing the value of R12 , the switching
frequency can be changed from 500kHz to 4MHz according to
Equation 2:
220  10 3
R T  k  = ------------------------------ – 14
f OSC  kHz 
FUNCTION
PCB Layout Recommendation
The PCB layout is a very important converter design step to make
sure the designed converter works well. For ISL8025, ISL8025A,
the power loop is composed of the output inductor L’s, the output
capacitor (COUT), the PHASE pins, and the PGND pin. It is
necessary to make the power loop as small as possible and the
connecting traces among them should be direct, short and wide.
The switching node of the converter, the PHASE pins, and the
traces connected to the node are very noisy, so keep the voltage
feedback trace away from these noisy traces. The input capacitor
should be placed as close as possible to the VIN pin. The ground
of input and output capacitors should be connected as close as
possible. The heat of the IC is mainly dissipated through the
thermal pad. Maximizing the copper area connected to the
thermal pad is preferable. In addition, a solid ground plane is
helpful for better EMI performance. It is recommended to add at
least 5 vias ground connection within the pad for the best
thermal relief.
(EQ. 2)
When using R12 to adjust the operational frequency, this also
sets external compensation mode. Please refer to the ISL8025,
ISL8025A datasheet for more details.
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Application Note 1806
ISL8025xEVAL3Z Schematic
J1
J2
L1
P4
A
VIN
1.0UH
PHASE
VO
2
P3
16
15
14
13
1
C5
10
C2
22UF
22UF
1
2
3
4
C3
0.1UF
12
11
10
9
PGND
PGND
SGND
FB
U1
R3
20
A
R2
100K
P7
C4
22PF
A
ISL8025IRTAJZ
EP
SYNC
PG
17
VIN
VDD
PG
SYNC
R1
EN
FS
SS
COMP
C1
C6
22UF
22UF
VIN
PHASE
PHASE
PHASE
R10
CH8
5
6
7
8
P5
200K
EN
A
A
SS
C7
220PF
R11
CSS
191K
R14
0.033UF
69.8K
VIN
DNP
C8
OPEN
R12
A
A
A
VIN
VIN
VIN
R5
2K
R4
EN
D1
200K
2
P6
PG
EN
SW1
R7
R6
200K
200K
3
ON
1
OFF
SYNC
2
P2
SYNC
SW2
3
PWM
1
PFM
3
1
Q1
R9
R8
OPEN
OPEN
2
P1
A
A
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Application Note 1806
Bill Of Materials
PART NUMBER
QTY UNITS
ISL8025REVAPCB
1
ea.
H1045-00220-50V5-T
1
ea.
H1045-00221-50V10-T
1
ea.
H1045-00333-16V10-T
1
REFERENCE
DESIGNATOR
DESCRIPTION
MANUFACTURER
MANUFACTURER PART
PWB-PCB, ISL8025, REVA, ROHS
IMAGINEERING INC ISL8025REVAPCB
C4
CAP, SMD, 0603, 22pF, 50V, 5%, C0G, ROHS
VENKEL
C7
CAP, SMD, 0603, 220pF, 50V, 10%, X7R, ROHS MURATA
GRM188R71H221KA01D
ea.
CSS
CAP, SMD, 0603, 33000pF, 16V, 10%, X7R,
ROHS
VENKEL
C0603X7R160-333KNE
C0603X7R160-104KNE
C0603C0G500-220JNE
H1045-00104-16V10-T
1
ea.
C3
CAP, SMD, 0603, 0.1µF, 16V, 10%, X7R, ROHS VENKEL
H1045-DNP
0
ea.
C8
CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS
H1065-00226-6R3V10-T
4
ea.
C1, C2, C5, C6 CAP, SMD, 1206, 22µF, 6.3V, 10%, X5R, ROHS MURATA
GRM31CR60J226KE19L
MPLCG0530L1R0
1
ea.
L1 (ISL8025) 1µH, 14.6mΩ, 5.6A, ROHS, SHIELDED
TOKIN
MPLCG0530L1R0
S13100004
1
ea.
L1 (ISL8025) 1µH, 13.7mΩ, 16A, ROHS, SHIELDED
WURTH
ELEKTRONIK
S13100004
FDV0530S-R78M
1
ea.
L1 (ISL8025A) 0.78µH, 20%, 14mΩ, 7.1A, ROHS, SHIELDED
TOKO
FDV0530S-R78M
131-4353-00
2
ea.
J1, J2
1514-2
4
ea.
5002
3
LTST-C170CKT
CONN-SCOPE PROBE TEST PT, COMPACT, PCB TEKTRONIX
MNT, ROHS
131-4353-00
P4, P5,
P7, P8
CONN-TURRET, TERMINAL POST, TH, ROHS
KEYSTONE
1514-2
ea.
P1, P2,
P6
CONN-MINI TEST POINT, VERTICAL, WHITE,
ROHS
KEYSTONE
5002
1
ea.
D1
LED-GaAs RED, SMD, 2x1.25mm, 100mW,
40mA, 10mcd, ROHS
LITEON/VISHAY
LTST-C170CKT
ISL8025
1
ea.
U1
IC-5A BUCK REGULATOR, 16P, QFN, 3x3, ROHS INTERSIL
ISL8025
2N7002-7-F-T
1
ea.
Q1
TRANSISTOR, N-CHANNEL, 3 LD, SOT-23, 60V, DIODES, INC.
115mA, ROHS
2N7002-7-F
H2505-DNP
0
ea
H2511-00R00-1/16W
1
ea.
R11
(ISL8025A)
RES, SMD, 0603, 0Ω, 1/16W, 1%, TF, ROHS
GENERIC
H2511-00200-1/10W1-T
1
ea.
R3
RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, ROHS
PANASONIC
RES, SM, 0603, 10Ω, 1/16W, 5%, TF, ROHS
GENERIC
R11 (ISL8025) RES, SMD, 0603, 0.1%, MF, DNP-PLACE
HOLDER
ERJ-3EKF20R0V
H2511-00100-1/16W5
1
ea.
R10
H2511-01003-1/10W1-T
1
ea.
R2, R14
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS VENKEL
CR0603-10W-1003FT
H2511-01913-1/10W1-T
1
ea.
R12
(ISL8025)
RES, SMD, 0603, 191k, 1/10W, 1%. TF, ROHS VENKEL
CR-0603-10W-1913FT
H2505-DNP
1
ea.
R12
(ISL8025A)
H2511-02003-1/10W1-T
4
ea.
R1, R4,
R6, R7
RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS VENKEL
H2511-DNP
0
ea.
R5, R8,
R9
RES, SMD, 0603, DNP-PLACE HOLDER, ROHS
GT11MSCBE-T
2
ea.
SW1, SW2
SWITCH-TOGGLE, SMD, 6 PIN, SPDT, 2POS,
ON-ON, ROHS
ITT INDUSTRIES/
C&K DIVISION
GT11MSCBE
5X8-STATIC-BAG
1
ea.
Place assy
in bag
BAG, STATIC, 5x8, ZIPLOC, ROHS
INTERSIL
212403-013
LABEL-SERIAL NUMBER
1
ea.
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RES, SMD, 0603, 0.1%, MF, DNP-PLACE
HOLDER
LABEL-FOR SERIAL NUMBER AND BOM REV # INTERSIL
CR0603-10W-2003FT
LABEL-SERIAL NUMBER
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November 10, 2014
Application Note 1806
ISL8025xEVAL3Z Board Layout
ISL8025
FIGURE 3. TOP LAYER COMPONENTS
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Application Note 1806
ISL8025xEVAL3Z Board Layout
(Continued)
FIGURE 4. TOP LAYER ETCH
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Application Note 1806
ISL8025xEVAL3Z Board Layout
(Continued)
FIGURE 5. SECOND LAYER ETCH
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Application Note 1806
ISL8025xEVAL3Z Board Layout
(Continued)
FIGURE 6. THIRD LAYER ETCH
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Application Note 1806
ISL8025xEVAL3Z Board Layout
(Continued)
FIGURE 7. BOTTOM LAYER ETCH
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Application Note 1806
ISL8025xEVAL3Z Board Layout
(Continued)
FIGURE 8. BOTTOM LAYER COMPONENTS
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Application Note 1806
Typical Performance Curves
100
PHASE 5V/DIV
3.3 V
-PFM
OUT
90
EFFICIENCY (%)
3.3 V
80
-PWM
OUT
VOUT RIPPLE 20mV/DIV
70
60
IL 2A/DIV
50
40
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
OUTPUT LOAD (A)
500ns/DIV
FIGURE 10. STEADY STATE AT 5A PWM
FIGURE 9. EFFICIENCY vs LOAD (1MHz 5VIN)
VOUT RIPPLE 100mV/DIV
VOUT RIPPLE 100mV/DIV
IL 2A/DIV
IL 2A/DIV
200µs/DIV
FIGURE 11. LOAD TRANSIENT (PWM)
200µs/DIV
FIGURE 12. LOAD TRANSIENT (PFM)
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
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