Intersil ISL8026EVAL3Z User manual

1
User Guide 033
ISL8026xEVAL3Z Evaluation Board User Guide
Description
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.
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.
Key Features
• 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
• Soft-stop output discharge during disabled
• Adjustable frequency from 500kHz to 4MHz - default at 1MHz
(2MHz for ISL8026A)
• External synchronization up to 4MHz
• Negative OC protection
References
ISL8026, ISL8026A Datasheet
Specifications
PART
NUMBER
IOUT
(MAX)
(A)
fSW RANGE
(MHz)
VIN
RANGE
(V)
VOUT
RANGE
(V)
PART SIZE
(2mm)
ISL8026
6
Programmable
0.5 to 4MHz 2.5 to
5.5
0.6 to
5.5 3x3
ISL8026A Programmable
1to4MHz
NOTES:
1. The Evaluation Boards’ default configuration are VOUT = 1.8V for
ISL8026EVAL3Z (fSW = 1MHz) and ISL8026AEVAL3Z (fSW =2MHz).
2. VREF is 0.6V.
Ordering Information
PART NUMBER DESCRIPTION
ISL8026EVAL3Z Evaluation Board For ISL8026
ISL8026AEVAL3Z Evaluation Board For ISL8026A
FIGURE 1. BLOCK DIAGRAM
VIN
VIN
PG
SYNC
PGND
FB
PGND
PGND/
SGND
VOUT
GND
VIN
GND
ISL8026
EPAD
EN FS SS
COMP
VIN
PHASE
PHASE
PHASE
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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 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.

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Recommended Equipment
The following materials are recommended to perform testing:
• 0V to 10V power supply with at least 10A source current
capability or 5V battery
• Electronic loads capable of sinking current up to 7A
• 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
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
depend on the desired output voltage of the regulator. The value
for the feedback resistor is typically between 0Ωand 200kΩ, as
shown in Equation 1.
If the output voltage desired is 0.6V, then R2is left unpopulated
and R1is shorted. For faster response performance, add 10pF to
47pF in parallel to R1. Check the Bode plot to insure optimum
performance.
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 =0and
R12 is open). By changing the value of R12 , the switching
frequency can be changed from 500kHz to 4MHz according to
Equation 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.
FIGURE 2. ISL8026EVAL3Z FIGURE 3. ISL8026AEVAL3Z
R2R1
VFB
VO VFB–
---------------------------


=(EQ. 1)
RTk 220 103

fOSC kHz
------------------------------ 14–= (EQ. 2)

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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 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.
PCB Layout Recommendation
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.
TABLE 1. SWITCH SETTINGS
SW1 ENABLE FUNCTION
1OFFDISABLEVO
3ONENABLEVO
SW2 MODE FUNCTION
1 PWM Fixed PWM frequency at light
load
3 PFM Force continuous mode
CSS F 3.33 tSS s=(EQ. 3)

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ISL8026xEVAL3Z Schematic
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Bill Of Materials
MANUFACTURER PART QTY UNIT
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER
ISL8026REVAPCB 1 ea. PWB-PCB, ISL8026, REVA, ROHS IMAGINEERING INC
C0603C0G500-220JNE 1 ea. C4 CAP, SMD, 0603, 22pF, 50V, 5%, C0G, ROHS VENKEL
GRM188R71H221KA01D 1 ea. C7 CAP, SMD, 0603, 220pF, 50V, 10%, X7R, ROHS MURATA
C0603X7R160-333KNE 1 ea. CSS CAP, SMD, 0603, 33000pF, 16V, 10%, X7R, ROHS VENKEL
C0603X7R160-104KNE 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 CONN-SCOPE PROBE TEST PT, COMPACT, PCB MNT, ROHS TEKTRONIX
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) RES, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER
1 ea. 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
CR0603-10W-2003FT 4 ea. R1, R4,
R6, R7
RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS VENKEL
0 ea. R5, R8,
R9
RES, SMD, 0603, DNP-PLACE HOLDER, ROHS
GT11MSCBE 2 ea. SW1, SW2 SWITCH-TOGGLE, SMD, 6 PIN, SPDT, 2POS, ON-ON, ROHS ITT INDUSTRIES/
C&K DIVISION

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ISL8026xEVAL3Z Board Layout
FIGURE 5. TOP LAYER COMPONENTS
ISL8026

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FIGURE 6. TOP LAYER ETCH
ISL8026xEVAL3Z Board Layout (Continued)

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FIGURE 7. SECOND LAYER ETCH
ISL8026xEVAL3Z Board Layout (Continued)

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FIGURE 8. THIRD LAYER ETCH
ISL8026xEVAL3Z Board Layout (Continued)

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FIGURE 9. BOTTOM LAYER ETCH
ISL8026xEVAL3Z Board Layout (Continued)