isl85403eval2z user guide

User Guide 010
ISL85403EVAL2Z Evaluation Board User Guide
Description
Key Features
The ISL85403EVAL2Z board allows quick evaluation of the
ISL85403 in the noninverting buck-boost configuration. It is a
cost effective solution for the low-power, wide input voltage
range point-of-load application where both stepping up and
stepping down voltage capabilities are required.
• Small, compact design
Specifications
• Convenient power connection
References
ISL85403 Datasheet
The design specifications of the ISL85403EVAL2Z are shown
in Table 1.
TABLE 1. SPECIFICATIONS
PARAMETERS
VALUES
Input Voltage (VIN)
8V to 40V
Output Voltage (VOUT)
12.0V
Max. Output Current (IOUT_MAX)
Ordering Information
PART NUMBER
ISL85403EVAL2Z
DESCRIPTION
ISL85403 Evaluation Board, buck-boost
configuration 12V output
1A
Switching Frequency
500kHz
Output Ripple
360mV at 1A Load
FIGURE 1. TOP VIEW
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• VIN range of 8V to 40V
1
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 | Copyright Intersil Americas LLC 2014, 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.
User Guide 010
Functional Description
The ISL85403 is a flexible switching regulator with an integrated
127mΩ high-side MOSFET. It can be used as a synchronous buck
converter, a 2-stage boost-buck converter, or a noninverting buck-boost converter.
The ISL85403EVAL2Z board demonstrates the operations of the
ISL85403 in the noninverting buck-boost configuration. The
ISL85403EVAL2Z board is shown in Figures 1 and 2.
The schematic is shown on page 4, bill of materials on page 4,
and PCB layers for reference start on page 7. Figures 4 through
15 show performance data taken from the evaluation board.
Operating Range
The board input voltage range is 8V to 40V. The output voltage is
set to 12V and can be changed by voltage feedback resistors R11
and R13, as shown in Equation 1:
V ref
R 13 = R 11  -------------------------------V OUT – v ref
(EQ. 1)
Note: In order to change to a higher output voltage, the output
capacitors have to be changed for the higher voltage rating.
The board is set to a default frequency of 500kHz (FS pin/R1 is
open). The switching frequency can be programmed to other
values by a resistor at R1. Refer to the ISL85403 datasheet for
the resistor value and the switching frequency. The switching
frequency can also be synchronized to external clock by
connecting the external clock to the SYNC terminal (J5).
source of the MOSFET. Keep this loop (output ceramic
capacitor, MOSFET and diode) as small as possible to
minimize the voltage spikes induced by the trace parasitic
inductance.
4. Place the output ceramic and aluminum capacitors close to
the power stage components as well.
5. Place vias (at least 9) in the bottom pad of the IC. The bottom
pad should be placed in ground copper plane with an area as
large as possible in multiple layers to effectively reduce the
thermal impedance.
6. Place the 4.7µF ceramic decoupling capacitor (C4 as shown
in the “ISL85403EVAL2Z Circuit Schematic” on page 3) as
close as possible to the IC’s VCC pin. Put multiple vias close to
the ground pad of this capacitor.
7. Keep the bootstrap capacitor close to the IC.
8. Keep the LGATE drive trace as short as possible and try to
avoid using vias in the LGATE drive path to achieve the lowest
impedance.
9. Place the output voltage sense trace close to the place that is
to be strictly regulated.
10. Place all the peripheral control components close to the IC.
Quick Test Setup
+-
- LOAD +
A
Inductor Current
In the noninverting buck-boost configuration, the inductor current
(IL) can be expressed as:
V OUT + V IN
I L = I OUT  -------------------------------V
(EQ. 2)
IN
The maximum inductor current happens at the condition of the
minimum input voltage and the maximum output current. The
inductor used in this noninverting buck-boost configuration
should have saturation current higher than the maximum
inductor current.
V OUT + V IN,min
I L sat  I OUT,max  -----------------------------------------V IN,min
(EQ. 3)
PCB Layout Guidelines
1. Place the input ceramic capacitors as closely as possible to
the IC VIN pin and power ground connecting to the power
diode. Keep this loop (input ceramic capacitor, IC VIN pin and
diode) as small as possible to minimize the voltage spikes
induced by the trace parasitic inductance. A bulk capacitor,
C5 (as shown in the “ISL85403EVAL2Z Circuit Schematic” on
page 3), is included to support long wire connections from
power supplies to the evaluation board.
2. Keep the phase node copper area small but large enough to
handle the load current.
FIGURE 3. ISL85403EVAL2Z BOARD SETUP
1. Connect the power supply to the input terminals VIN (J2) and
GND (J8). Connect the load terminals to the output VOUT (J6)
and GND (J3). Make sure the setup is correct prior to applying
any power or load to the board.
2. Adjust the power supply to 8V to 40V and turn it on.
3. Verify the output voltage is 12V and use oscilloscope to
monitor the phase node waveforms.
3. On the output side, place the output ceramic capacitors as
closely as possible to the cathode of the power diode and the
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User Guide 010
Bill of Materials
REF DES
PART NUMBER
QTY
DESCRIPTION
MANUFACTURER
C5
HHXA630ARA330MHA0G
1
Aluminum Electrolytic Capacitor, SMD, 8x10, 33µF, 63V, 20%, 40mΩ, ROHS
UNITED CHEMI-CON
C6
VARIOUS
1
CAP, SMD, 0603, 0.1µF, 50V, 10%, X7R, ROHS
VARIOUS
C3
VARIOUS
1
CAP, SMD, 0603, 1µF, 16V, 10%, X5R, ROHS
VARIOUS
C9
VARIOUS
1
CAP, SMD, 0603, 0.22µF, 25V, 10%, X7R, ROHS
VARIOUS
C10
VARIOUS
1
CAP, SMD, 0603, 470pF, 50V, 5%, NP0, ROHS
VARIOUS
C7
VARIOUS
1
CAP, SMD, 0603, 4700pF, 50V, 10%, X7R, ROHS
VARIOUS
C8
VARIOUS
1
CAP, SMD, 0603, 68pF, 50V, 10%, NP0, ROHS
VARIOUS
C1, C2
VARIOUS
2
CAP, SMD, 1206, 4.7µF, 50V, 10%, X5R, ROHS
VARIOUS
T521X337M016ATE025
1
CAP-TANT, LOW-ESR, SMD, 7.3x4.3x4, 330µF, 16V, 20%, 25mΩ, ROHS
KEMET
SS6P3LHM3/86A
2
DIODE-SCHOTTKY RECTIFIER, SMD, SMPC, 60V, 3A, ROHS
VISHAY
L1
744770118
1
COIL-PWR INDUCTOR, SMD, 12mm, 18µH, 20%, 4.2A, 0.032Ω, ROHS
WURTH
U1
ISL85403IRZ
1
IC-SWITCHING REGULATOR, 20P, QFN, 4X4, ROHS
INTERSIL
Q1
BSZ100N06LS3G
1
TRANSIST-MOS, N-CHANNEL, 8P, PG-TSDSON-8, 60V, 20A, ROHS
INFINEON
R2
VARIOUS
1
RES, SMD, 0603, 348k, 1/10W, 1%, TF, ROHS
VARIOUS
R3
VARIOUS
1
RES, SMD, 0603, 49.9k, 1/10W, 1%, TF, ROHS
VARIOUS
R4
VARIOUS
1
RES, SMD, 0603, 100Ω, 1/10W, 1%, TF, ROHS
VARIOUS
R5
VARIOUS
1
RES, SMD, 0603, 113k, 1/10W, 1%, TF, ROHS
VARIOUS
R8
VARIOUS
1
RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS
VARIOUS
R9
VARIOUS
1
RES, SMD, 0603, 4.7k, 1/10W, 1%, TF, ROHS
VARIOUS
R11
VARIOUS
1
RES, SMD, 0603, 28k, 1/10W, 1%, TF, ROHS
VARIOUS
R12
VARIOUS
1
RES, SMD, 0603, 0Ω, 1/10W, 1%, TF, ROHS
VARIOUS
R13
VARIOUS
1
RES, SMD, 0603, 2k, 1/10W, 1%, TF, ROHS
VARIOUS
0
Do not populate
C12
D1, D2
R1, R6, N/A
R7, R10,
C13
N/A
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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Typical Performance Curves
90
12.2
VIN = 8V
70
VIN = 18V
VIN = 8V
60
50
OUTPUT VOLTAGE (V)
FREQUENCY (%)
80
VIN = 36V
VIN = 24V
40
VIN = 18V
12.1
12.0
VIN = 24V
VIN = 36V
11.9
30
20
0.0
0.2
0.4
0.6
0.8
11.8
1.0
0.0
OUTPUT CURRENT (A)
0.2
0.4
0.6
OUTPUT CURRENT (A)
0.8
1.0
FIGURE 5. LOAD REGULATION
FIGURE 4. EFFICIENCY vs LOAD
VOUT
(AC-COUPLE)
VOUT
(AC-COUPLE)
IL
IL
PHASEi
PHASEi
PHASEo
PHASEo
FIGURE 7. OUTPUT RIPPLE AT 1A LOAD (VIN = 8V)
FIGURE 6. OUTPUT RIPPLE AT 0A LOAD (VIN = 8V)
OUT
VV
OUT
(AC-COUPLE)
(AC-COUPLE)
VOUT
VOUT
(AC-COUPLE)
(AC-COUPLE)
IL
IL
IL
IL
PHASEi
PHASEi
PHASEi
PHASEi
PHASEo
PHASEo
PHASEo
PHASEo
FIGURE 8. OUTPUT RIPPLE AT 0A LOAD (VIN = 36V)
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FIGURE 9. OUTPUT RIPPLE AT 1A LOAD (VIN = 36V)
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Typical Performance Curves (Continued)
VOUT
(AC-COUPLE)
VOUT
(AC-COUPLE)
IL
IL
FIGURE 10. LOAD TRANSIENT RESPONSE 0A<->1A, VIN = 8V
FIGURE 11. LOAD TRANSIENT RESPONSE 0A<->1A, VIN = 36V
VOUT
VOUT
IL
VOUT
IL
PHASEi
PHASEi
IL
PHASEo
PHASE
PHASEo
FIGURE 13. SOFT-START AT 1A LOAD (VIN = 8V)
FIGURE 12. SOFT-START AT 0A LOAD (VIN = 8V)
VOUT
VOUT
VOUT
IL
VOUT
IL
IL
IL
PHASEi
PHASEi
PHASEi
PHASEo
PHASEo
PHASEo
FIGURE 14. SOFT-START AT 0A LOAD (VIN = 36V)
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FIGURE 15. SOFT-START AT 1A LOAD (VIN = 36V)
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Board Layout
FIGURE 16. SILKSCREEN TOP
FIGURE 17. TOP LAYER
FIGURE 18. LAYER 2
FIGURE 19. LAYER 3
FIGURE 20. BOTTOM LAYER
FIGURE 21. SILKSCREEN BOTTOM
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