1
Application Note 1703
ISL8502AEVAL1Z: 2A Synchronous Buck Regulator with
Integrated MOSFETs
The ISL8502A is a synchronous buck controller with internal
MOSFETs packaged in a small 4mmx4mm QFN package. The
ISL8502A can support a continuous load of 2A and has a very
wide input voltage range. With the switching MOSFETs
integrated into the IC, the complete regulator footprint can be
very small and provide a much more efficient solution than a
linear regulator.
The ISL8502A is capable of standalone operation or it can be
used in a master slave combination for multiple outputs that
are derived from the same input rail. Multiple slave channels
can be individually programmed such that the internal clocks
are out-of-phase. This method minimizes the ripple on the
input rail.
The switching PWM controller drives two internal N-Channel
MOSFETs in a synchronous-rectified buck converter topology.
The synchronous buck converter uses voltage-mode control
with fast transient response. The switching regulator provides
a maximum static regulation tolerance of ±1% over line, load,
and temperature ranges. The output is user-adjustable by
means of external resistors down to 0.6V.
The output is monitored for undervoltage events. The switching
regulator also has over current protection. Thermal shutdown
is integrated. The ISL8502A features a bidirectional Enable pin
that allows the part to shut itself down and pull the enable pin
low at the same time. PGOOD Rising Delay (measured from
VOUT reaching regulation to PGOOD Rising) has been reduced
from 250ms (typical) for ISL8502 to 1ms (typical) for
ISL8502A (measured at 500kHz switching frequency).
Pin Configuration
ISL8502A
(24 LD QFN)
TOP VIEW
Features
• 2A Continuous Output Current
• Integrated MOSFETs for Small Regulator Footprint
• Adjustable Switching Frequency, 500kHz to 1.2MHz
• Tight Output Voltage Regulation, ±1% Over-Temperature
• Wide Input Voltage Range, 5V ±10% or 5.5V to 14V
• Wide Output Voltage Range, from 0.6V
• Simple Single-Loop Voltage-Mode PWM Control Design
• Input Voltage Feed-Forward for Constant Modulator Gain
• Fast PWM Converter Transient Response
• Lossless rDS(ON) High Side and Low Side Overcurrent
Protection
• Undervoltage Detection
• Integrated Thermal Shutdown Protection
• Power-Good Indication
• Adjustable Soft-Start
•QFN Package
- Compliant to JEDEC PUB95 MO-220
QFN (Quad Flat No Leads) package outline
- Near Chip Scale Package footprint, which improves PCB
efficiency and has a thinner profile
• Pb-Free (RoHS Compliant)
Applications
•Point of Load Applications
•Graphics Cards - GPU and Memory Supplies
• ASIC Power Supplies
• Embedded Processor and I/O Supplies
• DSP Supplies
1
2
3
4
5
6
18
17
16
15
14
13
24 23 22 21 20 19
789101112
VIN
PHASE
PHASE
PHASE
PHASE
PGND
PGOOD
SGND
EN
SYNCH
M/S
FS
COMP
FB
SS
PGND
PGND
PGND
VCC
PVCC
BOOT
VIN
VIN
VIN
GND
29
Ordering Information
PART
NUMBER
PART
MARKING
TEMP. RANGE
(°C)
PACKAGE
(Pb-free)
PKG.
DWG. #
ISL8502AIRZ
(Notes 1, 2, 3)
85 02AIRZ -40 to +85 24 Ld 4x4 QFN L24.4x4D
ISL8502AEVAL1Z Evaluation Board
NOTES:
1. Add “-T*” suffix for tape and reel. Please refer to TB347 for details on reel
specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free
material sets, molding compounds/die attach materials, and 100%
matte tin plate plus anneal (e3 termination finish, which is RoHS
compliant and compatible with both SnPb and Pb-free soldering
operations). Intersil Pb-free products are MSL classified at Pb-free peak
reflow temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see device information page
for ISL8502A. For more information on MSL please see tech brief
TB363.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 |Copyright Intersil Americas Inc. 2011. 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.
October 21, 2011
AN1703.0
Application Note 1703
2AN1703.0
October 21, 2011
What’s Inside
The Evaluation Board Kit contains the following materials:
• The ISL8502A EVAL REVD board
• The ISL8502A datasheet
•This EVAL KIT document
Recommended Equipment
The following materials are recommended to perform testing:
• 0V to 15V power supply with at least 5A source current
capability, battery, notebook AC adapter
• Two Electronic Loads capable of sinking current up to 5A
• Digital Multimeters (DMMs)
• 100MHz quad-trace Oscilloscope
• Signal generator (only if the SYNC function needs to be
evaluated)
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. Plus terminal to J1(VIN) and
negative return to J2(GND).
3. Verify that all positions are ON for S1, EN_all, EN_1, EN_2.
4. Turn on the power supply.
5. Verify the outputs voltages are 2.5V for VOUT1 and VOUT2.
Evaluating Other Output Voltages
The ISL8502AEVAL kit outputs are preset to 2.5V. For a quick
evaluation of output voltages between 0.6V and VIN -1.7V, the
following resistors need to be changed in the feedback
network as shown in Equations 1 and 2:
where R108 = 17.4kΩ; and VFB1 =0.6V
where R208 = 17.4kΩ; and VFB2 =0.6V
However, for reliable operation over the entire load and
temperature range, it is highly recommended to follow the
output filter and loop compensation network design guidelines
as listed in the ISL8502A datasheet.
Frequency
The ISL8502AEVAL can operate at switching frequencies from
500kHz to1.2MHz. R104 and R204 are used to program the
switching frequency through Equation 3:
Soft-start
C107, C207 can be used to adjust the soft-start time.
TABLE 1. SWITCH 1 SETTINGS
SW1 SKIP OPERATING MODE
1 NC No Connect
2 EN_ALL Enable or disable VOUT1 and VOUT2
3 EN1 Enable or disable VOUT1
4 EN2 Enable or disable VOUT2
R111 R108
()VOUT VFB1
⁄()1–[,]⁄=(EQ. 1)
R211 R208
()VOUT2 VFB2
⁄()1–[,]⁄=(EQ. 2)
R104and R204
()48000 fosc kHz[]()⁄=(EQ. 3)
Application Note 1703
3AN1703.0
October 21, 2011
ISL8502AEVAL1Z Schematic
1 AND 2
ENABLE
VOUT2
ON
OFF
REG 2
REG 1
VIN
VOUT1
GROUND CONNECTIONS FOR SCOPE PROBES
1
D200
2
R203
1
R200
C207
36
4.7UH
10K
95.3K
OPEN
17.4K
5.49K
22UF
0.1UF
5.49K
10UF
10UF
10UF
10UF
IKN0403000
DNP
0.1UF
10K
4.7UH
47PF
36
OPEN
0
470PF
DNP
0.1UF
10K
2N7002
75 75
2N7002
DNP
0
20K
0
470PF
0.01UF
174
17.4K
0.1UF
1000PF
DNP
22UF
100UF
5.49K5.49K
U100
1
10
11
12
13
14
15
16
17
18
19
2
20
21
22
23
24
25
3
4
5
6
7
8
9
R107
R108
R110
R111
R109
R104
R103
R101
1
10
11
12
13
14
15
16
17
18
19
2
21
22
23
24
25
3
4
5
6
7
8
9
R202
R207
R210
R208
R211
R201
1
2
JP3
1
2
JP2
1
2
D100
2
1
R105
R205
Q1
1
3
2
Q2
1
3
2
Q3
3
1
2
R3
R1
R2
R6
Q4
1
3
2
R5
R4
Q5
1
3
2
Q6
3
1
2
J1
1
J2
1
TP100
1
TP104
1
TP105
1
TP109
1
TP103
1
TP112
1
TP204
1
TP205
1
TP3
1
TP111
1
TP211
1
TP200
1
TP209
1
TP203
1
J4
1
J6
1
P1
1
P6
1
TP110
1
J3
1
1
D1
2
1
D2
2
1
TP212
1
S1
1
2
3
45
6
7
8
L100
1
2
L200
1
2
C103
1
2
1
C202
1
2
C109
1
2
1
2
C108
1
2
2
C110
1
2
1
C106
1
2
C206
1
2
C100A
1
2
1
2
C105
1
2
C102
1
2
C107
1
2
1
2
C104
1
2
1
2
C200B
1
2
C200A
1
2
C205
1
2
J10
2
3
4
1
J9
2
3
4
1
J8
2
3
4
1
J7
2
3
4
1
JP1
C100B
R102
R100
20
U200
C204
100UF
J5
174
2
C210
C208
20K
2
C203
10K
0.01UF
47PF
1
R204
95.3K
C209
1000PF
R209
TP210
4.99K
ON
ON
1
ON
ON
2
3
4
22
21
20
19
23
1
3
2
4
6
5
16
18
17
14
25
15
13
24
11
12
8
7
10
9
PACKAGE
EP
24 PIN
MLFP
22
21
20
19
23
1
3
2
4
6
5
16
18
17
14
25
15
13
24
11
12
8
7
10
9
PACKAGE
EP
24 PIN
MLFP
Application Note 1703
4AN1703.0
October 21, 2011
TABLE 2. BILL OF MATERIALS
PART NUMBER QTY UNITS
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER MANUFACTURER PART
ISL8502EVAL1ZREVEPCB 1 ea SEE LABEL-
RENAME BOARD
PWB-PCB,
ISL8502EVAL1Z, REV E,
SOIC, ROHS
IMAGINEERING INC ISL8502EVAL1ZREVEPCB
GRM21BR71C475KA73L 2 ea C111, C211 CAP, SMD, 0805, 4.7µF,
16V, 10%, X7R, ROHS
MURATA GRM21BR71C475KA73L
H1044-00104-16V10-T 2 ea C102, C202 CAP, SMD, 0402, 0.1µF,
16V, 10%, X7R, ROHS
VENKEL C0402X7R160-104KNE
MURATA GRM155R71C104KA88D
PANASONIC ECJ-0EX1C104K
TAIYO YUDEN EMK105B7104KV-F
YAGEO CC0402KRX7R7BB104
KEMET C0402C104K4RACTU
TDK C1005X7R1C104K
H1044-00105-10V10-T 2 ea C103, C203 CAP, SMD, 0402, 1.0µF,
10V, 10%, X5R, ROHS
MURATA GRM155R61A105KE15D
VENKEL C0402X5R100-105KNE
TAIYO YUDEN LMK105BJ105KV-F
AVX 0402ZD105KAT2A
H1044-00150-50V5-T 2 ea C108, C208 CAP, SMD, 0402, 15pF,
50V, 5%, NP0, ROHS
MURATA GRM36COG150J050AQ
PANASONIC ECU-E1H150JCQ
VENKEL C0402COG500-150JNE
H1044-00153-16V10-T 2 ea C107, C207 CAP, SMD, 0402, 0.015µF,
16V, 10%, X7R, ROHS
PANASONIC ECJ-0EB1C153K
VENKEL C0402X7R160-153KNE
AVX 0402YC153KAT2A
MURATA GRM155R71C153KA01D
H1044-00471-50V10-T 2 ea C110, C210 CAP, SMD, 0402, 470pF,
50V, 10%, X7R, ROHS
PANASONIC ECJ-0EB1H471K
VENKEL C0402X74500-471KNE
H1044-00821-50V10-T 2 ea C109, C209 CAP, SMD, 0402, 820pF,
50V, 10%, X7R, ROHS
PANASONIC ECJ-0EB1H821K
H1044-DNP 0 ea C106, C206 CAP, SMD, 0402, DNP-
PLACE HOLDER, ROHS
H1046-DNP 0 ea C112, C113 CAP, SMD, 0805, DNP-
PLACE HOLDER, ROHS
H1065-00106-25V10-T 4 ea C100A, C100B,
C200A, C200B
CAP, SMD, 1206, 10µF,
25V, 10%, X5R, ROHS
VENKEL C1206X5R250-106KNE
H1082-00107-10V20-T 2 ea C105, C205 CAP, SMD, 1210, 100µF,
10V, 20%, X5R, ROHS
TAIYO YUDEN LMK325BJ107MM-T
111-0702-001 1 ea VIN CONN-GEN, BIND.POST,
INSUL-RED, THMBNUT-
GND
JOHNSON COMPONENTS 111-0702-001
KEYSTONE 7006
111-0703-001 1 ea GND CONN-GEN, BIND.POST,
INSUL-BLK, THMBNUT-
GND
JOHNSON COMPONENTS 111-0703-001
KEYSTONE 7007
131-4353-00 4 ea J7-J10 CONN-SCOPE PROBE TEST
PT, COMPACT, PCB MNT,
ROHS
TEKTRONIX 131-4353-00
1514-2 6 ea J3-J6, P1, P2 CONN-TURRET, TERMINAL
POST, TH, ROHS
KEYSTONE 1514-2
Application Note 1703
5AN1703.0
October 21, 2011
5002 17 ea a) TP3, TP100,
TP103-TP105,
TP109-TP112,
CONN-MINI TEST POINT,
VERTICAL, WHITE, ROHS
KEYSTONE 5002
5002 0 ea b) TP200, TP203-
TP205, TP209-
TP212
CONN-MINI TEST POINT,
VERTICAL, WHITE, ROHS
KEYSTONE 5002
69190-202HLF 3 ea JP1-JP3 CONN-HEADER, 1X2,
RETENTIVE, 2.54mm,
0.230X 0.120, ROHS"
BERG/FCI 69190-202HLF
SPC02SYAN 1 ea JP3 CONN-JUMPER,
SHORTING, 2 PIN, BLACK,
GOLD, ROHS
SULLINS SPC02SYAN
1N4148WS-7-F-T 2 ea D100, D200 DIODE-RECTIFIER, SMD,
SOD-323, 2P, 75V,
150mA, ROHS
DIODES INC. 1N4148WS-7-F
BAT54-T 0 ea DNP (D1, D3) DIODE-SCHOTTKY, SMD,
SOT23, 3P, 30V, 200mA,
SINGLE DIODE
FAIRCHILD BAT54
PDS560-13 0 ea DNP (D2, D4) DIODE-RECTIFIER, SMD,
POWER DI5, 3P, 60V, 5A,
ROHS
DIODES INC. PDS560-13
LTST-C170CKT 2 ea LED1, LED2 LED-GaAs RED, SMD,
2mmx1.25mm, 100mW,
40mA, 10mcd, ROHS
LITEON/VISHAY LTST-C170CKT
ROHM SML-210LTT86
STANLEY
ELECTRIC
BR112H-TR
CDRH8D28NP-4R7NC 2 ea L100, L200 COIL-PWR INDUCTOR,
SMD, 8.3mm, 4.7µH, 30%,
3.4A, ROHS, SHIELDED
SUMIDA
ELECTRIC, CO.
CDRH8D28NP-4R7NC
ISL8502AIRZ 2 ea U100, U200 IC-2A BUCK REGULATOR,
24P, QFN, 4X4, ROHS
INTERSIL ISL8502AIRZ
2N7002-7-F-T 2 ea Q3, Q6 TRANSISTOR, N-CHANNEL,
3 LD, SOT-23, 60V,
115mA, ROHS
DIODES, INC. 2N7002-7-F
ON SEMICONDUCTOR 2N7002LT1G
MMBT2222ALT1G-T 4 ea Q1, Q2, Q4, Q5 TRANSISTOR, NPN, 3 LD,
SOT23, 40V, 600mA,
ROHS
H2510-00360-1/16W5-T 2 ea R3, R5 RES, SMD, 0402, 36Ω,
1/16W, 5%, TF, ROHS
YAGEO RC0402JR-0736RL
VENKEL CR0402-16W-360JT
H2510-00750-1/16W5-T 2 ea R1, R6 RES, SMD, 0402, 75Ω,
1/16W, 5%, TF, ROHS
PANASONIC ERJ2GEJ0750
VENKEL CR0402-16W-750JT
H2510-00R00-1/16W-T 3 ea R100, R105,
R205
RES, SMD, 0402, 0Ω,
1/16W, 5%, TF, ROHS
VENKEL CR0402-16W-00T
PANASONIC ERJ-2GE0JR00
H2510-01002-1/16W1-T 4 ea R101, R102,
R201, R202
RES, SMD, 0402, 10k,
1/16W, 1%, TF, ROHS
PANASONIC ERJ-2RKF1002X
VENKEL CR0402-16W-1002FT
ROHM MCR01MZPF1002
YAGEO RC0402FR-0710KL
VISHAY/DALE CRCW040210K0FKED
TABLE 2. BILL OF MATERIALS (Continued)
PART NUMBER QTY UNITS
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER MANUFACTURER PART
Application Note 1703
6AN1703.0
October 21, 2011
H2510-01401-1/16W1-T 2 ea R110, R210 RES, SMD, 0402, 1.4k,
1/16W,1%, TF, ROHS
VISHAY/DALE CRCW04021K40FKED
STACKPOLE RMCF0402FT1K40
VENKEL CR0402-16W-1401FT
H2510-02802-1/16W1-T 4 ea R108, R109,
R208, R209
RES, SMD, 0402,
28k,1/16W, 1%, TF, ROHS
VENKEL CR0402-16W-2802FT
PANASONIC ERJ-2RKF2802X
ROHM MCR01MZPF2802
YAGEO RC0402FR-0728KL
VISHAY/DALE CRCW040228K0FKED
H2510-04991-1/16W1-T 1 ea R203 RES, SMD, 0402, 4.99k,
1/16W, 1%, TF, ROHS
KDA RK73H1E4991F
VENKEL CR0402-16W-4991FT
H2510-05491-1/16W1-T 2 ea R2, R4 RES, SMD, 0402, 5.49k,
1/16W, 1%, TF, ROHS
H2510-06041-1/10W1-T 2 ea R111, R211 RES, SMD, 0402, 6.04k,
1/10W, 1%, TF, ROHS
PANASONIC ERJ2RKF6041X
H2510-09532-1/16W1-T 2 ea R104, R204 RES, SMD, 0402, 95.3k,
1/16W, 1%, TF, ROHS
YAGEO RC0402FR-0795K3L
VENKEL CR0402-16W-9532FT
H2510-DNP 0 ea R103, R107,
R200, R207
RES, SMD, 0402, DNP,
DNP, DNP, TF, ROHS
H2511-00100-1/10W1-T 2 ea R112, R212 RES, SMD, 0603, 10Ω,
1/10W, 1%, TF, ROHS
KOA RK73H1JT10R0F
VENKEL CR0603-10W-10R0FT
H2515-DNP 0 ea R113, R114 RES, SMD, 2512, DNP,
DNP, DNP, TF, ROHS
IKN0403000 1 ea S1 (Install
according to
silkscreen)
SWITCH-DIP, SMD, 4P,
SLIDE, SPST, LP, ROHS
APEM IKN0403000
4-40X1/2-SCREW 4 ea Four corners SCREW, 4-40X1/2in, PAN,
NYLON, PHILLIPS, ROHS
4-40X3/4-STANDOFF 4 ea Four corners STANDOFF, 4-40X3/4in,
F/F, HEX, NYLON, ROHS
KEYSTONE 1902D
5X8-STATIC-BAG 1 ea Place assy in bag BAG, STATIC, 5X8, ZIPLOC,
ROHS
INTERSIL 212403-013
DNP 0 ea C104, C204 DO NOT POPULATE OR
PURCHASE
LABEL-DATE CODE 1 ea LABEL-FOR DATE CODE
AND BOM REV #
INTERSIL LABEL-DATE CODE
LABEL-RENAME BOARD 1 ea RENAME PCB TO:
ISL8502AEVAL1Z
LABEL, TO RENAME
BOARD
INTERSIL LABEL-RENAME BOARD
TABLE 2. BILL OF MATERIALS (Continued)
PART NUMBER QTY UNITS
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER MANUFACTURER PART
Application Note 1703
7AN1703.0
October 21, 2011
ISL8502AEVAL1Z Board Layout
FIGURE 1. TOP COMPONENTS
FIGURE 2. TOP LAYER ETCH
ISL8502AEVAL1Z
Application Note 1703
8AN1703.0
October 21, 2011
FIGURE 3. 2ND LAYER ETCH
FIGURE 4. 3RD LAYER ETCH
ISL8502AEVAL1Z Board Layout (Continued)
Application Note 1703
9
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
AN1703.0
October 21, 2011
FIGURE 5. BOTTOM LAYER COMPONENTS (MIRRORED)
FIGURE 6. BOTTOM LAYER ETCH (MIRRORED)
ISL8502AEVAL1Z Board Layout (Continued)
