an1860

Application Note 1860
ISL85415DEMO1Z Wide VIN 500mA Synchronous Buck
Regulator
Description
Quick Setup Guide
The ISL85415DEMO1Z kit is intended for use for
point-of-load applications sourcing from 3V to 36V. The kit is
used to demonstrate the performance of the ISL85415 Wide
VIN Low Quiescent Current High Efficiency Sync Buck
Regulator with 500mA output current.
The ISL85415 is offered in a 4mmx3mm 12 Ld DFN package
with 1mm maximum height. The converter occupies
1.516 cm2 area.
Key Features
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 GND (P5).
3. Turn on the power supply.
4. Verify the output voltage is 3.3V for VOUT.
Evaluating the Other Output Voltage
• No compensation required
The ISL85415DEMO1Z kit output is preset to 3.3V; however,
output voltages can be adjusted from 0.6V to 15V. The output
voltage programming resistor, R2, will depend on the desired
output voltage of the regulator and the value of the feedback
resistor R1, as shown in Equation 1.
• Integrated high-side and low-side NMOS devices
0.6
R 2 = R 1  ---------------------------
V
– 0.6
• Wide input voltage range 3V to 36V
• Synchronous operation for high efficiency
• Selectable PFM or forced PWM mode at light loads
• Internal fixed (500kHz) or adjustable switching frequency
300kHz to 2MHz
• Continuous output current up to 500mA
• Internal or external soft-start
• Minimal external components required
• Power-good and enable functions available
(EQ. 1)
OUT
If the output voltage desired is 0.6V, then R1 is shorted. Please
note that if VOUT is less than 1.8V, the switching frequency and
compensation must be changed for 300kHz operation due to
minimum on-time limitation. Please refer to datasheet
ISL85415 for further information.
Table 1 on page 2 shows the component selection that should
be used for the respective VOUTs.
Recommended Equipment
The following materials are recommended to perform testing:
• 0V to 50V power supply with at least 2A source current
capability
• Electronic Loads capable of sinking current up to 1.5A
• Digital multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
FIGURE 1. FRONT OF EVALUATION BOARD ISL85415DEMO1Z
May 16, 2014
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1
FIGURE 2. BACK OF EVALUATION BOARD ISL85415DEMO1Z
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas LLC 2013, 2014. All Rights Reserved.
1-888-INTERSIL or 1-888-468-3774 | 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.
Application Note 1860
TABLE 1. EXTERNAL COMPONENT SELECTION
VOUT
(V)
L1
(µH)
COUT
(µF)
R1
(k)
R2
(k)
CFB
(pF)
RFS
(k)
RCOMP
(k)
CCOMP
(pF)
12
45
10
90.9
4.75
22
115
100
470
5
22
2x22
90.9
12.4
100
120
100
470
3.3
22
2x22
90.9
20
100
120
100
470
2.5
22
2x22
90.9
28.7
100
120
100
470
1.8
22
22
100
50
22
120
50
470
Frequency Control
The ISL85415 has an FS pin that controls the frequency of
operation. Programmable frequency allows for optimization
between efficiency and external component size. It also allows
low frequency operation for low VOUTs when minimum on time
would limit the operation otherwise. Default switching frequency
is 500kHz when FS is tied to VCC (R10 = 0). By removing R10 the
switching frequency could be changed from 300kHz
(R12 = 340k) to 2MHz (R12 = 32.4k). Please refer to datasheet
ISL85415 for calculating the value of R10. Do not leave this pin
floating.
Disabling/Enabling Function
ISL85415DEMO1Z board has EN pin tied to VCC via R7. This
keeps the part enabled all the time. To disable the part, remove
R7 and populate R8 with a 0 resistor.
SYNC Control
The ISL85415 evaluation board has a SYNC pin that allows
external synchronization frequency to be applied. Default board
configuration has R6 = 200k to VCC, which defaults to PWM
operation mode and also to the pre-selected switching frequency
set by R12 (see datasheet and previous section “Frequency
Control” for details). If this pin is tied to GND the IC will operate in
PFM mode. For PFM operation, remove R6 and populate R9 with
0 resistor.
Soft-Start /COMP Control
R15 selects between internal (R15 = 0) and external soft-start.
R11 selects between internal (R11 = 0) and external
compensation. Please refer to Pin Description Table (Page 3) of
the ISL85415 datasheet.
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Application Note 1860
ISL85415DEMO1Z Schematic
R10
OPEN
VCC
CSS
0.033UF
R15
OPEN
? A
SS
1 SS
SYNC
P4
C3
P7
C10
150UF
C1
10UF
C2
10UF
2 SYNC
VO
C6
22UF
C5
22UF
FS 12
COMP11
3 BOOT
0.1UF
VIN
R12
120K
4 VIN
6 PGND
PG 8
EN 7
EP
DFN12
P5
C7
470PF
C8
OPEN
ISL85415
R11
OPEN
R3
100K
VO
R1
FB 10
VCC 9
5 PHASE
L1
22UH
VCC
VCC
PG
EN
C9
1UF
90.9K
P8
C4
100PF
R2
20K
A
A
VIN
P9
A
VCC
R7
200K
R6
200K
SYNC
EN
P2
P1
R9
OPEN
A
PG
R8
OPEN
A
NOTE: If the IC is used in an application where the input test leads have large parasitic inductance, the input electrolytic
capacitor C10 may be added to prevent transient voltages on the input pin.
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Application Note 1860
ISL85415DEMO1Z Bill of Materials
PART NUMBER
REFERENCE
DESIGNATOR
QTY
UNIT
DESCRIPTION
MANUFACTURER
ISL85400EVAL2ZREVAPCB
1
ea
INTERSIL
LABEL-RENAME BOARD PWB-PCB,
ISL85400EVAL2Z, REVA,
ROHS
EEE-FK1H151P-T (DNP)
1
ea
C10 (OPTIONAL)
PANASONIC
CAP, SMD, 10.3mm,
150µF, 50V, 20%, ROHS,
ALUM.ELEC.
EEE-FK1H151P
H1044-00101-50V5-T
1
ea
C4
CAP, SMD, 0402, 100pF, MURATA
50V, 5%, C0G, ROHS
GRM1555C1H101JZ01D
H1044-00333-16V10-T
1
ea
CSS
CAP, SMD, 0402,
33000pF, 16V, 10%,
X7R, ROHS
MURATA
GRM36X7R333K016AQ
H1044-00471-50V10-T
1
ea
C7
CAP, SMD, 0402, 470pF, PANASONIC
50V, 10%, X7R, ROHS
H1044-DNP
0
ea
C8
CAP, SMD, 0402,
DNP-PLACE HOLDER,
ROHS
H1045-00104-50V10-T
1
ea
C3
CAP, SMD, 0603, 0.1µF, AVX
50V, 10%, X7R, ROHS
06035C104KAT2A
H1045-00105-16V10-T
1
ea
C9
CAP, SMD, 0603, 1µF,
16V, 10%, X5R, ROHS
MURATA
GRM188R61C105KA12D
H1065-00106-50V10-T
2
ea
C1, C2
CAP, SMD, 1206, 10µF,
50V, 10%, X5R, ROHS
TDK
C3216X5R1H106K
H1065-00226-6R3V10-T
2
ea
C5, C6
CAP, SMD, 1206, 22µF,
6.3V, 10%, X5R, ROHS
MURATA
GRM31CR60J226KE19L
74408943220
1
ea
L1
COIL-PWR INDUCTOR,
SMD, 4.8mm, 22µH,
20%, 1.1A, ROHS
Wurth Electronics
74408943220
5000
2
ea
P4, P7
CONN-MINI TEST PT,
VERTICAL, RED, ROHS
KEYSTONE
5000
5001
2
ea
P5, P9
CONN-MINI TEST PT,
VERTICAL, BLK, ROHS
KEYSTONE
5001
5002
2
ea
P1, P2
CONN-MINI TEST POINT, KEYSTONE
VERTICAL, WHITE, ROHS
5002
ISL85415FRZ
1
ea
U1
IC-500mA BUCK
REGULATOR, 12P, DFN,
3x4, ROHS
H2510-01003-1/16W1-T
1
ea
R3
RES, SMD, 0402, 100k, PANASONIC
1/16W, 1%, TF, ROHS
ERJ2RKF1003
H2510-01203-1/16W1-T
1
ea
R12
RES, SMD, 0402, 120k, ROHM
1/16W, 1%, TF, ROHS
MCR01MZPF1203
H2510-02002-1/16W1-T
1
ea
R2
RES, SMD, 0402, 20k,
1/16W, 1%, TF, ROHS
ERJ2RKF2001
H2510-02003-1/16W1-T
2
ea
R6, R7
RES, SMD, 0402, 200k, ROHM
1/16W, 1%, TF, ROHS
MCR01MZPF2003
H2510-09092-1/16W1-T
1
ea
R1
RES, SMD, 0402, 90.9k, VISHAY/DALE
1/16W, 1%, TF, ROHS
CRCW040290K9FKED
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INTERSIL
PANASONIC
MANUFACTURER PART
ISL85400EVAL2ZREVAPCB
ECJ-0EB1H471K
ISL85415FRZ
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May 16, 2014
Application Note 1860
ISL85415DEMO1Z Bill of Materials (Continued)
PART NUMBER
REFERENCE
DESIGNATOR
QTY
UNIT
DESCRIPTION
MANUFACTURER
H2510-DNP
0
ea
R8-R11, R15
RES, SMD, 0402, DNP,
DNP, DNP, TF, ROHS
2X3-STATIC-BAG
1
ea
PLACE ASSY IN BAG
BAG, STATIC, 2x3, ZIP
LOC
LABEL-DATE CODE
1
ea
AFFIX TO BACK OF PCB
LABEL-DATE CODE_BOM INTERSIL
REV#_SERIAL# LABEL
ON ZIL & QUEL
LABEL-DATE CODE
LABEL-RENAME BOARD
1
ea
RENAME TOP PCB TO:
ISL85415DEMO1Z
LABEL, TO RENAME
BOARD
LABEL-RENAME BOARD
TBD
INTERSIL
MANUFACTURER PART
S-6509
ISL85415DEMO1Z Board Layout
FIGURE 3. SILK SCREEN TOP
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Application Note 1860
ISL85415DEMO1Z Board Layout (Continued)
FIGURE 4. SILKSCREEN BOTTOM
Efficiency Curves
FSW = 800kHz, TA = +25°C
100
100
VIN = 15V
VIN = 12V
VIN = 6V
90
90
85
85
80
VIN = 33V
75
70
VIN = 24V
65
V
V
V
V
V
6
VIN = 15V
65
55
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VIN = 33V
70
55
FIGURE 5. EFFICIENCY vs LOAD, PFM, VOUT = 5V
VIN = 24V
75
60
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
VIN = 12V
80
60
50
0
VIN = 6V
95
EFFICIENCY (%)
EFFICIENCY (%)
95
50
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 6. EFFICIENCY vs LOAD, PWM, VOUT = 5V
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Application Note 1860
Efficiency Curves
FSW = 800kHz, TA = +25°C (Continued)
100
100
90
90
85
85
80
75
70
VIN = 33V
VIN = 24V
65
75
70
60
55
50
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT LOAD (A)
FIGURE 7. EFFICIENCY vs LOAD, PFM, VOUT = 3.3V
FIGURE 8. EFFICIENCY vs LOAD, PWM, VOUT = 3.3V
100
100
95
VIN = 15V
VIN = 12V
80
75
70
VIN = 33V
VIN = 24V
75
70
65
55
55
50
0.30 0.35 0.40 0.45 0.50
VIN = 24V
0
VIN = 33V
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT LOAD (A)
FIGURE 10. EFFICIENCY vs LOAD, PWM, VOUT = 1.8V
FIGURE 9. EFFICIENCY vs LOAD, PFM, VOUT = 1.8V
5.020
5.018
VIN = 6V
5.012
5.010
VIN = 24V
5.006
OUTPUT VOLTAGE (V)
VIN = 12V
5.014
5.008
VIN = 6V
5.015
VIN = 15V
5.016
OUTPUT VOLTAGE (V)
VIN = 5V
80
60
0.05 0.10 0.15 0.20 0.25
VIN = 12V
85
60
50
0
VIN = 15V
90
EFFICIENCY (%)
EFFICIENCY (%)
85
65
95
VIN = 5V
90
5.004
VIN = 33V
VIN = 24V
65
55
0
VIN = 5V
80
60
50
VIN = 12V
VIN = 15V
95
EFFICIENCY (%)
EFFICIENCY (%)
VIN = 5V
VIN = 12V
VIN = 15V
95
5.010
VIN = 33V
5.005
VIN = 24V
5.000
VIN = 12V
4.995
VIN = 15V
4.990
4.985
4.980
VIN = 33V
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 11. VOUT REGULATION vs LOAD, PWM, VOUT = 5V
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4.975
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 12. VOUT REGULATION vs LOAD, PFM, VOUT = 5V
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Application Note 1860
Efficiency Curves
FSW = 800kHz, TA = +25°C (Continued)
3.345
3.336
VIN = 12V
VIN = 15V
3.340
3.332
VIN = 12V
VIN = 5V
3.330
3.328
3.326
VIN = 24V
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.334
VIN = 33V
3.335
VIN = 24V
3.325
3.320
VIN = 33V
0
3.310
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0
OUTPUT LOAD (A)
FIGURE 13. VOUT REGULATION vs LOAD, PWM, VOUT = 3.3V
1.785
1.776
1.780
VIN = 15V
1.775
1.774
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 14. VOUT REGULATION vs LOAD, PFM, VOUT = 3.3V
1.777
VIN = 12V
1.773
1.772
VIN = 5V
1.771
VIN = 5V
VIN = 15V
1.775
1.770
VIN = 12V
VIN = 24V
1.765
VIN = 33V
1.760
1.770
1.769
VIN = 15V
3.330
3.315
3.324
3.322
VIN = 5V
0
VIN = 33V
VIN = 24V
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 15. VOUT REGULATION vs LOAD, PWM, VOUT = 1.8V
Typical Performance Curves
1.755
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
FIGURE 16. VOUT REGULATION vs LOAD, PFM, VOUT = 1.8V
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C.
LX 20V/DIV
LX 20V/DIV
VOUT 2V/DIV
VOUT 2V/DIV
IL 500mA/DIV
EN 20V/DIV
PG 2V/DIV
PG 2V/DIV
5ms/DIV
5ms/DIV
FIGURE 17. START-UP AT NO LOAD, PFM
FIGURE 18. START-UP AT 500mA, PWM
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Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
LX 20V/DIV
VOUT 2V/DIV
LX 5V/DIV
IL 500mA/DIV
PG 2V/DIV
50µs/DIV
50ns/DIV
FIGURE 19. SHUTDOWN AT 500mA, PWM
FIGURE 20. JITTER AT 500mA, PWM
LX 20V/DIV
LX 20V/DIV
VOUT 10mV/DIV
VOUT 10mV/DIV
IL 100mA/DIV
IL 200mA/DIV
5ms/DIV
500ns/DIV
FIGURE 21. STEADY STATE AT NO LOAD, PFM
FIGURE 22. STEADY STATE AT NO LOAD, PWM
LX 20V/DIV
LX 20V/DIV
VOUT 50mV/DIV
VOUT 10mV/DIV
IL 500mA/DIV
IL 200mA/DIV
1µs/DIV
10µs/DIV
FIGURE 23. STEADY STATE AT 500mA LOAD, PWM
FIGURE 24. LIGHT LOAD OPERATION AT 20mA, PFM
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Application Note 1860
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
VOUT 50mV/DIV
VOUT 100mV/DIV
IL 500mA/DIV
IL 500mA/DIV
200µs/DIV
200µs/DIV
FIGURE 25. LOAD TRANSIENT, PFM
FIGURE 26. LOAD TRANSIENT, PWM
LX 20V/DIV
LX 20V/DIV
VOUT 2V/DIV
VOUT 2V/DIV
IL 1A/DIV
IL 500mA/DIV
PG 2V/DIV
2µs/DIV
20µs/DIV
FIGURE 28. OVERCURRENT PROTECTION, PWM
FIGURE 27. PFM TO PWM TRANSITION
LX 20V/DIV
LX 20V/DIV
VOUT 2V/DIV
SYNC 2V/DIV
IL 1A/DIV
PG 2V/DIV
50ms/DIV
FIGURE 29. OVERCURRENT PROTECTION HICCUP, PWM
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200ns/DIV
FIGURE 30. SYNC AT 500mA LOAD, PWM
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Application Note 1860
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
LX 20V/DIV
LX 20V/DIV
VOUT 5V/DIV
VOUT 5V/DIV
IL 0.5A/DIV
IL 0.5A/DIV
PG 2V/DIV
PG 2V/DIV
10µs/DIV
200µs/DIV
FIGURE 31. NEGATIVE CURRENT LIMIT, PWM
FIGURE 32. NEGATIVE CURRENT LIMIT RECOVERY, PWM
VOUT 2V/DIV
PG 2V/DIV
500µs/DIV
FIGURE 33. OVER-TEMPERATURE PROTECTION, PWM
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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