isl8026xeval3z user guide

User Guide 033
ISL8026xEVAL3Z Evaluation Board User Guide
Description
Key Features
The ISL8026EVAL3Z and ISL8026AEVAL3Z are intended for use
by customers with requirements for point-of-load applications
sourcing from 2.5V to 5.5V. The ISL8026EVAL3Z and
ISL8026AEVAL3Z are used to demonstrate the performance of
the ISL8026 and ISL8026A, low quiescent high efficiency
synchronous buck regulator.
• High efficiency synchronous buck regulator with up to 95%
efficiency
• 1% reference accuracy over load/line/temperature
(-40°C to +85°C)
• Start-up with prebiased output
• Internal soft-start - 1ms or adjustable
The ISL8026 and ISL8026A 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
• Adjustable frequency from 500kHz to 4MHz - default at 1MHz
(2MHz for ISL8026A)
Specifications
PART
NUMBER
IOUT
(MAX)
(A)
ISL8026
6
ISL8026A
• External synchronization up to 4MHz
fSW RANGE
(MHz)
Programmable
0.5 to 4MHz
Programmable
1 to 4MHz
VIN
VOUT
RANGE RANGE
(V)
(V)
• Negative OC protection
References
PART SIZE
(2mm)
ISL8026, ISL8026A Datasheet
2.5 to
5.5
0.6 to
5.5
Ordering Information
3x3
PART NUMBER
NOTES:
1. The Evaluation Boards’ default configuration are VOUT = 1.8V for
ISL8026EVAL3Z (fSW = 1MHz) and ISL8026AEVAL3Z (fSW = 2MHz).
DESCRIPTION
ISL8026EVAL3Z
Evaluation Board For ISL8026
ISL8026AEVAL3Z
Evaluation Board For ISL8026A
2. VREF is 0.6V.
ISL8026
GND
PHASE
VIN
PHASE
VIN
PHASE
VIN
VOUT
VIN
GND
PGND
PGND
EPAD
PGND/
SGND
PG
COMP
SS
FB
FS
EN
SYNC
FIGURE 1. BLOCK DIAGRAM
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
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User Guide 033
FIGURE 2. ISL8026EVAL3Z
Recommended Equipment
FIGURE 3. ISL8026AEVAL3Z
The following materials are recommended to perform testing:
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.
• 0V to 10V power supply with at least 10A source current
capability or 5V battery
VFB
R 2 = R 1  ---------------------------
 VO – VFB
• Electronic loads capable of sinking current up to 7A
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 the Bode plot to insure optimum
performance.
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
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.
3. Connect the output load to VOUT, the plus terminal to VOUT, P3
and the negative return to PGND, P7.
4. Verify that the position is set to PWM for SW2.
5. Verify that the position is set to ON for SW1.
6. Turn on the power supply.
7. Verify that the output voltage is 1.8V for VOUT.
Operating Range
(EQ. 1)
Frequency Control
The ISL8026 and ISL8026A 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 ISL8026EVAL3Z and
2MHz for ISL8026AEVAL3Z 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 
(EQ. 2)
When using R12 to adjust the operational frequency, this also
sets the external compensation mode. Please refer to the
ISL8026, ISL8026A datasheet for more details.
By default, the ISL8026EVAL3Z is configured for the operating
conditions shown in the “Quick Setup Guide”. The board can also
support a wider operating range. Modifying the operating
conditions will change the performance results.
The ISL8026EVAL3Z and ISL8026AEVAL3Z outputs 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
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User Guide 033
PCB Layout Recommendation
Soft-start Control
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.
CSS  F  = 3.33  t SS  s 
(EQ. 3)
CSS must be less than 33nF to insure proper soft-start reset after
fault condition.
Switches Control
The ISL8026EVAL3Z and ISL8026AEVAL3Z boards contain SW1
and SW2 for various controls of the ISL8026, ISL8026A
circuitries. Table 1 details this function.
TABLE 1. SWITCH SETTINGS
SW1
ENABLE
1
OFF
DISABLE VO
3
ON
ENABLE VO
SW2
MODE
1
PWM
Fixed PWM frequency at light
load
3
PFM
Force continuous mode
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FUNCTION
The PCB layout is a very important converter design step to make
sure the designed converter works well. For ISL8026, ISL8026A,
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.
FUNCTION
3
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ISL8026xEVAL3Z Schematic
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FIGURE 4. SCHEMATIC
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User Guide 033
Bill Of Materials
MANUFACTURER PART
QTY
UNIT
ISL8026REVAPCB
1
ea.
C0603C0G500-220JNE
1
ea.
GRM188R71H221KA01D
1
ea.
C0603X7R160-333KNE
1
C0603X7R160-104KNE
REFERENCE
DESIGNATOR
DESCRIPTION
MANUFACTURER
PWB-PCB, ISL8026, REVA, ROHS
IMAGINEERING INC
C4
CAP, SMD, 0603, 22pF, 50V, 5%, C0G, ROHS
VENKEL
C7
CAP, SMD, 0603, 220pF, 50V, 10%, X7R, ROHS
MURATA
ea.
CSS
CAP, SMD, 0603, 33000pF, 16V, 10%, X7R, ROHS
VENKEL
1
ea.
C3
CAP, SMD, 0603, 0.1µF, 16V, 10%, X7R, ROHS
VENKEL
0
ea.
C8
CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS
GRM31CR60J226KE19L
4
ea.
C1, C2, C5, C6
CAP, SMD, 1206, 22µF, 6.3V, 10%, X5R, ROHS
MURATA
ETQP3W1R0WFN
1
ea.
L1 (ISL8026)
1µH, 6.9mΩ, 8.1A, ROHS, SHIELDED
PANASONIC
ETQP3WR68WFN
1
ea.
L1 (ISL8026A)
0.68µH, 4.9mΩ, 9.6A, ROHS, SHIELDED
PANASONIC
131-4353-00
2
ea.
J1, J2
1514-2
4
ea.
P4, P5,
P7, P8
CONN-TURRET, TERMINAL POST, TH, ROHS
KEYSTONE
5002
3
ea.
P1, P2,
P6
CONN-MINI TEST POINT, VERTICAL, WHITE, ROHS
KEYSTONE
LTST-C170CKT
1
ea.
D1
LED-GaAs RED, SMD, 2x1.25mm, 100mW, 40mA,
10mcd, ROHS
LITEON/VISHAY
ISL8026
1
ea.
U1
IC-5A BUCK REGULATOR, 16P, QFN, 3x3, ROHS
INTERSIL
2N7002-7-F
1
ea.
Q1
TRANSISTOR, N-CHANNEL, 3 LD, SOT-23, 60V, 115mA,
ROHS
DIODES, INC.
0
ea
R11 (ISL8026)
1
ea.
CONN-SCOPE PROBE TEST PT, COMPACT, PCB MNT, ROHS TEKTRONIX
RES, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER
R11 (ISL8026A) RES, SMD, 0603, 0Ω, 1/16W, 1%, TF, ROHS
GENERIC
ERJ-3EKF20R0V
1
ea.
R3
RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, ROHS
PANASONIC
CR0603-10W-1003FT
1
ea.
R2, R14
RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS
VENKEL
CR-0603-10W-1913FT
1
ea.
R12 (ISL8026)
RES, SMD, 0603, 191k, 1/10W, 1%. TF, ROHS
VENKEL
1
ea.
R12 (ISL8026A) RES, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER
4
ea.
R1, R4,
R6, R7
RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS
0
ea.
R5, R8,
R9
RES, SMD, 0603, DNP-PLACE HOLDER, ROHS
GT11MSCBE
2
ea.
SW1, SW2
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CR0603-10W-2003FT
VENKEL
SWITCH-TOGGLE, SMD, 6 PIN, SPDT, 2POS, ON-ON, ROHS ITT INDUSTRIES/
C&K DIVISION
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User Guide 033
ISL8026xEVAL3Z Board Layout
ISL8026
FIGURE 5. TOP LAYER COMPONENTS
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User Guide 033
ISL8026xEVAL3Z Board Layout
(Continued)
FIGURE 6. TOP LAYER ETCH
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User Guide 033
ISL8026xEVAL3Z Board Layout
(Continued)
FIGURE 7. SECOND LAYER ETCH
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User Guide 033
ISL8026xEVAL3Z Board Layout
(Continued)
FIGURE 8. THIRD LAYER ETCH
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User Guide 033
ISL8026xEVAL3Z Board Layout
(Continued)
FIGURE 9. BOTTOM LAYER ETCH
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ISL8026xEVAL3Z Board Layout
(Continued)
FIGURE 10. BOTTOM LAYER COMPONENTS
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Typical Performance Curves
100
PHASE 5V/DIV
3.3 V
90
-PFM
OUT
EFFICIENCY (%)
3.3 V
80
-PWM
OUT
VOUT RIPPLE 20mV/DIV
70
60
50
40
0.0
IL 2A/DIV
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 11. EFFICIENCY vs LOAD (1MHz 5VIN)
FIGURE 12. STEADY STATE AT 5A PWM
VOUT RIPPLE 100mV/DIV
VOUT RIPPLE 100mV/DIV
IL 2A/DIV
IL 2A/DIV
200µs/DIV
FIGURE 13. LOAD TRANSIENT (PWM)
200µs/DIV
FIGURE 14. 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 document is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
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