an1630

Application Note 1630
Author: Tu Bu
6A Low Quiescent Current High Efficiency Synchronous
Buck Regulator
Description
Quick Setup Guide
The ISL8016CIR1EVAL1Z kit is intended for use by individuals
with requirements for Point-of-Load applications sourcing from
2.7V to 5.8V. The ISL8016CIR1EVAL1Z simple smallest factor
evaluation board is used for a quick and easy demonstration of
the performance of the ISL8016 low quiescent high efficiency
synchronous buck regulator.
The ISL8016 is offered in a 3mmx4mm 20 Ld QFN package
with 1mm maximum height. The complete converter occupies
can be as small as 0.15in2 area.
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, J1,
and the negative return to PGND, J2.
3. Connect the output load to VOUT, the plus terminal to
VOUT1, J3 and the negative return to PGND, J4.
4. Verify that the position is PWM for S1.
5. Verify the position is OPEN for S2 and S3.
6. Verify that the position is ON for S4 and S5.
Key Features
7. Turn on the power supply.
• High Efficiency Synchronous Buck Regulator with up to 97%
Efficiency
• 0.8% Reference Accuracy Over-Temperature/Load/Line
• Fixed Output Voltage Option
• ±10% Output Voltage Margining
• Adjustable Current Limit
• Current Sharing Capable
• Start-up with Pre-Biased Output
• Internal Soft-Start - 1ms or Adjustable
• Soft-Stop Output Discharge During Disabled
• Adjustable Frequency from 500kHz to 4MHz - Default at 1MHz
• External Synchronization up to 4MHz - Master to Slave Phase
Shifting Capability
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
8. Verify the output voltage is 1.8V for VOUT1.
Evaluating the Other Output Voltage
The ISL8016CIR1EVAL1Z kit output is preset to 1.8V for
VOUT1, 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 0Ω and 200kΩ, as
shown in Equation 1.
VFB
R2 = R1 ⎛ ------------------------⎞
⎝ VO – VFB⎠
(EQ. 1)
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 bode
plot to insure optimum performance.
Frequency Control
ISL8016 has 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 when FS is tied to VIN (R6 = 0 and R5 is
open). By connecting R5 to GND, the switching frequency could
be changed from 500kHz (R5 = 390k) to 4MHz (R5 = 40k)
according to Equation 2:
200 ⋅ 10 3
R T [ kΩ ] = ------------------------------ – 10
f OSC [ kHz ]
(EQ. 2)
When using R5 to adjust the operational frequency, this also
sets external compensation mode. Please refer to the ISL8016
datasheet (FN7616) for more details.
May 17, 2011
AN1630.1
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
Copyright Intersil Americas Inc. 2011. 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 1630
Soft-start Control
Swtiches Control
Short CSS1 to SGND for internal soft-start (approximately 1ms).
Populate CSS1 to adjust the soft-start time. This capacitor, along
with an internal 1.6mA current source, sets the soft-start interval
of the converter, tSS.
The ISL8016 evaluation board contains S1 thru S5 for various
controls of the ISL8016 circuitries. Table 1 details this function.
CSS1 [ μF ] = 3.33 ⋅ t SS [ s ]
(EQ. 3)
CSS must be less than 33nF to insure proper soft-start reset after
fault condition.
Synchronization Control
The ISL8016 can be synchronized from 700kHz to 4MHz by an
external signal applied to the SYNCIN pin. The rising edge on the
SYNCIN triggers the rising edge of the PHASE pulse. Make sure that
the minimum on-time of the PHASE node is greater than 140ns.
SYNCOUT is a 250µA current pulse signal output triggered by the
rising edge of the clock or the SYNCIN signal (whichever is
greater in frequency) to drive the other ISL8016 and avoid the
system’s beat frequencies effects. To implement time shifting
between the master circuit to the slave, it is recommended to
add a capacitor, C13 as shown in the schematic. The time delay
from SYNCOUT_Master to SYNCIN_Slave is calculated in pF using
the following:
C 6 [ pF ] = 0.357 ⋅ t [ ns ]
(EQ. 4)
Where, t is the desired time shift between the master and the
slave circuits in ns. Care must be taken to include PCB parasitic
capacitance of ~3pF to 10pF.
The maximum should be limited to 1/Fs-100ns to insure that
SYNCOUT has enough time to discharge before the next cycle
starts.
2
TABLE 1. SWITCH SETTINGS
S1
MODE
FUNCTION
1
PWM
Fixed PWM frequency at light load
3
PFM
Force continuous mode
S2
ISET
PROGRAM OUTUT CURRENT
1
LOW
SET OUTPUT LOAD TO 2A.
-
OPEN
SET OUTPUT LOAD TO 6A.
3
HIGH
SET OUTPUT LOAD TO 4A.
S3
VSET
SET OUTPUT MARGIN
1
LOW
SET OUTPUT VOLTAGE -10%.
-
OPEN
NO OUTPUT VOLTAGE MARGIN
3
HIGH
SET OUTPUT VOLTAGE +10%.
S4
ENABLE
1
OFF
DISABLE VOUT1
3
PFM
ENABLE VOUT1
S5
ENABLE
1
OFF
DISABLE VOUT2
3
PFM
ENABLE VOUT2
FUNCTION
FUNCTION
AN1630.1
ISL8016CIR1EVAL1Z Schematic
3
31
31
C13
C11
330PF
C26
2
1
VFB
SYNCOUT2
16
A
1
2
R21
20
19
18
17
200K
R22
100K
R29
100K
EN2
VIN
SGND
SYNCIN
R19
0
VIN
R20
16
1
21
SYNCOUT
15
2
3
3
15
4
4
14
5
5
13
10
SS
12
SYNCIN2
J5
C17
CSS2
DNP
OPEN
A
A
C19
C20
VOUT2
1
2
4
C14
A
47PF
A
J6
FB2
FB2
PGND
A
COMP2
COMP2
DRAWN BY:
SS2
C18
22UF 22UF OPEN OPEN
PGND
COMP
SS
COMP
ISET
FS
VSET
EN
11
A
ISET
17
C27
47PF
VOUT2
NOTE:
PLEASE KEEP COMP PIN TRACES SHORT
PLEASE KEEP FB1, FB2 PINS TRACES SHORT
A
PGND
SLAVE
ISL8016IRZ
PG
FS
VFB
18
200K
9
VIN
EN
SYNCIN
SYNCIN3
19
8
VSET
SGND
20
7
PG2
R25
6
6
21
PGND
22UF 22UF OPEN OPEN
PGND
SYNCOUT
C24
PGND
LX
ISL8016IRZ
PG
C23
A
PGND
U3
C22
LX
LX
9
10
VIN
C21
LX
LX
8
VOUT2
2
EP
VIN
EP
VIN
7
0.68UH
LX
1
VIN
0
COMP2
47K
L2
VIN
L3
R3
A
1.0UH
VIN
A
VIN
100K
22UF
A
22UF
R7
A
R14
A
A
C12
R4
C6
OPEN
SS2
200K
VIN
EN211
FS2 12
VSET13
ISET14
C25
22UF
0
R5
DNP
3
A
J4
PGND
COMP1
220PF
OPEN
R6
1
2
4
2
A
200K 47PF
DATE:
ENGINEER:
RELEASED BY:
DATE:
TITLE:
UPDATED BY:
DATE:
SS2
JUN XIAO
06/11/09
TESTER
MASK#
JUN XIAO
DATE:
ISL8016
EVALUATION BOARD
SCHEMATIC
HRDWR ID
ISL8016
REV.
A
Application Note 1630
LX2
JC111_07XX
A
C5
CSS1
Q2
PG2
2
2N7002
100K FB1
17
VFB
C4
R1
R2
18
SGND
A
A
0
19
PGND
4 VOUT1
3
2
2
1
1
2
C10
22UF 22UF OPEN OPEN
R13
20
PGND
SS
DNP
C9
C8
COMP
PG1
PG2
Q1
A
R9
D2
PGND
1
2K
20
A
SYNCIN
ISET
2N7002
SYNCIN1
SYNCOUT1
0
J3
C7
FB2
SYNCOUT
FS
PG1
9
VOUT1
L1
R24
ISL8016IRZ
PG
VOUT2
1.0UH
MASTER
VIN
VSET
OFF
R26
100K
D1
A
8
EN
100K
PG1
10
VIN
LX
3
R27
7
PGND
EN1
2K
R16
C2
22UF
J2
R17
R11
C1
22UF
JC111_07XX
R28
100K
VSET
OFF
DNP
A
ON/EX
VIN
A
R18
3
ON/EX
LX
A
VIN
S3 1
S4 1
EP
EN1
OFF
EN2
A
3
2
S5 1
3
3
2
EN2
22UF
OPEN
A
VIN
LX
PFM
JC111_07XX
J1
VIN
S1 1
OPEN
A
R12
100K
VIN
PWM
C3
SYNCIN1
2
R15
4 LX1
16
2
S2 1
OFF
3
4
R23
100K
ON/EX
5
SYNCIN1
6
R8
100K
3 ON/EX
VSET
1
2
EN1
11
FS1 12
VSET13
ISET14
SS1 15
ISET
ISET
VIN
21
R10
100K
2
VIN
3
VIN
JC111_07XX
VIN
AN1630.1
Application Note 1630
TABLE 2. BILL OF MATERIALS
PART NUMBER
REFERENCE
DESIGNATOR
QTY UNITS
DESCRIPTION
MANUFACTURER
PART #
MANUFACTURER
ISL8016CIR1EVAL1ZREVAPCB
1
ea
SEE LABEL-RENAME
BOARD
PWB-PCB,
ISL8016CIR1EVAL1Z, REVA,
ROHS
TBD
ISL8016CIR1EVAL1ZREVAPCB
H1045-00150-50V5-T
1
ea
C4
CAP, SMD, 0603, 15pF, 50V,
5%, NPO, ROHS
MURATA
GRM39COG150J050AD
H1045-00221-50V5-T
1
ea
C5
CAP, SMD, 0603, 220pF, 50V, VENKEL
5%, C0G, ROHS
C0603COG500-221JNE
H1045-00333-50V5-T
1
ea
CSS1
CAP, SMD, 0603, 33000pF,
25V, 5%, X7R, ROHS
06035C333JAT2A
H1045-DNP
0
ea
C3, C6, CSS2
CAP, SMD, 0603, DNP-PLACE MURATA
HOLDER, ROHS
H1065-00226-6R3V20-T
5
ea
C1, C2, C7,
C8, C10
CAP, SMD, 1206, 22µF, 6.3V,
20%, X5R, ROHS
H1065-00476-6R3V20-T
1
ea
C9
CAP, SMD, 1206, 47µF, 6.3V, MURATA
20%, X5R, ROHS
H1065-DNP
0
ea
C19, C20,
C23, C24
CAP, SMD, 1206, DNP-PLACE
HOLDER, ROHS
IHLP-5050CE-01-1R0M
1
ea
L1
COIL-PWR INDUCTOR, SMD,
13mm, 1.0µH, 20%, 24A,
ROHS
VISHAY
IHLP-5050CE-01-1R0M
111-0702-001
2
ea
J1, J3
CONN-GEN, BIND.POST,
INSUL-RED, THMBNUT-GND
JOHNSON COMPONENTS
111-0702-001
111-0703-001
2
ea
J2, J4
CONN-GEN, BIND.POST,
INSUL-BLK, THMBNUT-GND
JOHNSON COMPONENTS
111-0703-001
131-4353-00
2
ea
LX1, VOUT1
CONN-SCOPE PROBE TEST
PT, COMPACT, PCB MNT,
ROHS
TEKTRONIX
131-4353-00
1514-2
2
ea
J5, J6
CONN-TURRET, TERMINAL
POST, TH, ROHS
KEYSTONE
1514-2
5000
14
ea
EN1, EN2, FB2, PG1, CONN-MINI TEST PT,
PG2, SS2, ISET, VSET, VERTICAL, RED, ROHS
COMP2, SYNCIN1SYNCIN3, SYNCOUT1,
SYNCOUT2
KEYSTONE
5000
LTST-C170CKT
2
ea
D1, D2
LITEON/VISHAY
LED-GaAs RED, SMD,
2X1.25mm, 100mW, 40mA,
10mcd, ROHS
LTST-C170CKT
B340B-13-F-T
2
ea
D1, D2
DIODE-SCHOTTKY, SMD,
SMB, 2P, 40V, 3A, ROHS
DIODES INC.
B340B-13-F
ISL8016IRZ
1
ea
MASTER
IC-ADJ. 6A BUCK
REGULATOR, 20P, QFN, 3X4,
ROHS
INTERSIL
ISL8016IRZ
2N7002-7-F-T
2
ea
Q1, Q2
TRANSISTOR, N-CHANNEL, 3 DIODES, INC.
LD, SOT23, 60V, 115mA,
ROHS
H2505-DNP
0
ea
R6, R9 ,R20, R28
RESISTOR,SMD,0603,0.1%,
MF,DNP-PLACE HOLDER
H2510-DNP
0
ea
R4, R7, R13, R14,
R19, R21, R22, R25,
R29
RES,SMD,0402, DNP, DNP,
DNP,TF,ROHS
4
AVX
GRM36COG680J050AQ
GRM31CR60J476ME19L
2N7002-7-F
AN1630.1
Application Note 1630
TABLE 2. BILL OF MATERIALS (Continued)
PART NUMBER
REFERENCE
DESIGNATOR
QTY UNITS
DESCRIPTION
MANUFACTURER
H2511-00200-1/10W1-T
1
ea
R24
RES,SMD,0603,20ohm,1/1
0W,1%,TF,ROHS
H2511-00R00-1/10W-T
1
ea
R18
RES, SMD, 0603, 0Ω, 1/10W, VENKEL
TF, ROHS
CR0603-10W-000T
H2511-01003-1/10W1-T
9
ea
R2, R3, R8, R10-R12,
R16, R23, R26
RES, SMD, 0603, 100k,
1/10W, 1%, TF, ROHS
VENKEL
ERJ-3EKF1003V
ROHM
CR0603-10W-1003FT
YAGEO
MCR03EZPFX1003
VISHAY/DALE
ERJ-3EKF1004V
PANASONIC
ERJ-3EKF2003V
VENKEL
CR0603-10W-2003FT
ROHM
MCR03EZPFX2003
KOA
RK73H1JTTD2003F
VISHAY/DALE
CRCW06031M00FKEA
H2511-02003-1/10W1-T
2
ea
R1, R5
RES, SMD, 0603, 200k,
1/10W, 1%, TF, ROHS
PANASONIC
MANUFACTURER
PART #
ERJ-3EKF20R0V
H2511-DNP
0
ea
R17, R27
RES, SMD, 0603, DNP-PLACE
HOLDER, ROHS
H2514-DNP
0
ea
R15
RES,SMD, 1210, DNP, DNP,
DNP, TF, ROHS
GT11MSCBE-T
3
ea
S1, S4, S5
SWITCH-TOGGLE, SMD, 6PIN, ITT INDUSTRIES/C&K
SPDT, 2POS, ON-ON, ROHS
DIVISION
GT11MSCBE
GT13MSCBE
2
ea
S2, S3
SWITCH-TOGGLE, SMD, 6PIN, ITT INDUSTRIES/C&K
DIVISION
SPDT, 3POS, ON-OFF-ON,
ROHS
GT13MSCBE
DNP
0
ea
C11-C14, C17, C18,
C21, C22, C25-C27
DO NOT POPULATE OR
PURCHASE
DNP
0
ea
L2, L3, LX2, VOUT2, U3, DO NOT POPULATE OR
SLAVE
PURCHASE
5
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout
ISL8016CIR1EVAL1Z
FIGURE 1. TOP LAYER COMPONENTS
6
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout (Continued)
FIGURE 2. TOP LAYER ETCH
7
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout (Continued)
FIGURE 3. SECOND LAYER ETCH
8
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout (Continued)
FIGURE 4. THIRD LAYER ETCH
9
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout (Continued)
FIGURE 5. BOTTOM LAYER ETCH
10
AN1630.1
Application Note 1630
ISL8016CIR1EVAL1Z Board Layout (Continued)
FIGURE 6. BOTTOM LAYER COMPONENTS
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
11
AN1630.1
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