an1492

Application Note 1492
Author: Huong Doan
ISL8088EVAL1Z REVA Dual 800mA Low Quiescent
Current 2.25MHz High Efficiency Synchronous Buck
Regulator
Description
Quick Setup Guide
The ISL8088EVAL1Z kit is intended for use by individuals with
requirements for Point-of-Load applications sourcing from 2.75V
to 5.5V. The ISL8088EVAL1Z evaluation board is used to
demonstrate the performance of the ISL8088 low quiescent
current mode converter.
1. Ensure that the circuit is correctly connected to the supply and
loads prior to applying any power.
The ISL8088 is offered in a 3mmx3mm 10 Ld DFN package with
1mm maximum height. The complete converter occupies less
than 1.8cm2 area.
4. Turn on the power supply.
2. Connect the bias supply to VIN. Plus terminal to VIN and
negative return to PGND.
3. Verify that position is ON for SW2 and SW3.
5. Verify the output voltage is 2.5V for VOUT1 and 1.8V for VOUT2.
Evaluating the Other Output Voltage
Key Features:
• Dual 800mA High Efficiency Synchronous Buck Regulator with
up to 97% Efficiency
• 800mA Guaranteed Output Current per channel
• Power-Good (PG) output with 1ms Delay
• 2.75V to 5.5V Supply Voltage
• 3% Output Accuracy Over-Temperature/Load/Line
• Start-up with Pre-biased Output
• Internal Digital Soft-Start - 2ms
The ISL8088EVAL1Z kit output is preset to 2.5V for VOUT1 and
1.8V for VOUT2; however, output voltages can be adjusted from
0.6V to 3.3V. The output voltage programming resistor, R2 (or R5
in Channel 2), will depend on the desired output voltage of the
regulator. The value for the feedback resistor is typically between
0Ω and 750kΩ as shown in Equation 1.
Let’s set R3 = 100kΩ, then R2 will be:
(EQ. 1)
VOUT
R2 = R3 ⎛ ------------------ – 1⎞
⎝ VFB
⎠
If the output voltage desired is 0.6V, then R3 is left unpopulated
and short R2. For faster response performance, add 10pF in
parallel to R2.
• Soft-Stop Output Discharge During Disabled
• 30µA Quiescent Supply Current in PFM Mode
• Selectable Forced PWM Mode and PFM Mode
Mode Control
• External Synchronization up to 4MHz
• Typical 6.5µA Logic Controlled Shutdown Current
• 100% Maximum Duty Cycle for Lowest Dropout
• Internal Current Mode Compensation
• Peak Current Limiting.
The ISL8088 has a SYNC pin that controls the operation mode.
SYNC pin connect to logic high or input voltage VIN for PFM
mode; connect to logic low or ground for forced PWM mode.
Connect to an external function generator for Synchronization.
Negative edge trigger. Do not leave this pin floating.
TABLE 1. SWITCH SETTINGS
• Over-Temperature Protection
• Independent Enable
Recommended Equipment
SW2&3
ENABLE
ON/OFF CONTROL
1
OFF
Disable VOUT
3
ON
Enable VOUT
SW1
SKIP
1
PWM
Fixed PWM frequency at light load
3
PFM
Force continuous mode
The following materials are recommended to perform testing:
• 0V to 10V Power Supply with at least 3A source current
capability or 5V battery
• Electronic Loads capable of sinking current up to 3A
FUNCTION
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
February 14, 2014
AN1492.2
1
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 2009, 2010, 2014. 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.
ISL8088EVAL1ZREVA Schematic
LX1_S
1
2
1
2
3
4 LX1
C8
OPEN
C1
10UF
4
3
VIN
VIN
A
LX2
A
PGND
U1
A
VIN
2
1
VOUT1
R1
100K
1
2
SYNC
0
SYNC
2
3
S1 1
C9
OPEN
A
11
R14
20
A
FB2
10
EN2
9
8
LX2
7
6
1
2.2UH
L2
2
SYNC
ISL8088IRZ
VOUT2
VOUT2
C4
10UF
R13
20
C6
OPEN
VOUT2
VOUT2_S
1
2
4
A
A
C3
10PF
R2
316K
R5
200K
C5
10PF
PGND2
PGND
A
PGND1
A
4
5
C2
10UF
PGND
A
2
VOUT2_S
A
PFM
PWM
LX1
2
FB2
EN2
PG
LX2
SYNCH
FB1
EN1
VIN
LX1
NC
PGND
EP
Application Note 1492
SYNC
R11
3
VOUT1_S 4
C7
OPEN
1
3
VOUT1
VOUT1
VOUT1_S
2.2UH
L1
FB1
EN1
3
PGND
R3
100K
A
VIN
VIN
R6
100K
PG
VIN
A
R7
100K
R10
2K
2
R4
100K
SGND
2
3
S2 1
ON/EX
OFF
EN1
SGND
EN2
2
3
S3 1
R9
OPEN
ON/EX
OFF
EN2
PG
EN2
1
PG
2N7002
Q2
2
EN1
D2
31
EN1
A
NOTE:
PLEASE KEEP FB1, FB2 PINS TRACES SHORT
A
A
A
DRAWN BY:
RELEASED
HUONG DOAN
BY:
TU BUI / HUONG DOAN
UPDATED
BY:
DATE:
03/20/2008
DATE:
DATE:
ENGINEER:
HUONG DOAN
TITLE:
DATE:
ISL8088
3/20/08
DUAL 800MA LOW IQ BUCK
SCHEMATIC
AN1492.2
February 14, 2014
Application Note 1492
TABLE 2. BILL OF MATERIALS
PART NUMBER
QTY
UNIT
ISL8088EVAL1ZREVAPCB
1
ea
H1045-00100-50V5-T
2
ea
REFERENCE
DESIGNATOR
C3, C5
DESCRIPTION
MANUFACTURER
PART
MANUFACTURER
PWB-PCB,
ISL8088EVAL1Z,
REVA, ROHS
TITAN
ISL8088EVAL1ZREVAPCB
CAP, SMD, 0603, 10pF,
50V, 5%, COG, ROHS
YAGEO
CC0603JRNP09BN100
VENKEL
C0603COG500-100JNE
KEMET
C0603C100J5GACTU
MURATA
GRM1885C1H100JA01D
AVX
06035A100JAT2A
VENKEL
C0805X5R6R3-106KNE
KEMET
C0805C106K9PACTU
AVX
08056D106KAT2A
MURATA
GRM21BR60J106KE19L
TAIYO YUDEN
JMK212BJ106KG
TOKO
MDT2520-CR2R2M
H1045-DNP
0
ea
C9
CAP, SMD, 0603, DNPPLACE HOLDER, ROHS
H1046-00106-6R3V10-T
3
ea
C1, C2, C4
CAP, SMD, 0805, 10µF,
6.3V, 10%, X5R, ROHS
H1046-DNP
0
ea
C6 to C8
CAP, SMD, 0805, DNPPLACE HOLDER, ROHS
MDT2520-CR2R2M
2
ea
L1, L2
COIL-PWR INDUCTOR,
SMD, 2520, 2.2µH, 20%,
1.35A, ROHS
1514-2
6
ea
PGND, PGND1,
PGND2, VIN,
VOUT1,VOUT2
CONN-TURRET, TERMINAL KEYSTONE
POST, TH, ROHS
1514-2
5000
4
ea
EN1, EN2, PG,
SYNC
CONN-MINI TEST PT,
VERTICAL, RED, ROHS
KEYSTONE
5000
5001
1
ea
SGND
CONN-MINI TEST PT,
VERTICAL, BLK, ROHS
KEYSTONE
5001
LTST-C170CKT
1
ea
D2
LED-GaAs RED, SMD,
2mmx1.25mm, 100mW,
40mA, 10mcd, ROHS
LITEON/VISHAY
LTST-C170CKT
ROHM
SML-210LTT86
STANLEY ELEC.
BR112H-TR
INTERSIL
ISL8088IRZ
ISL8088IRZ
1
ea
U1
IC-DUAL SYNC. BUCK
REGULATOR, 10P, DFN,
3X3, ROHS
2N7002-T
1
ea
Q2
NAT’L SEMICNDTR
TRANSISTOR,
N-CHANNEL, 3LD, SOT-23,
MOTOROLA
60V, 115mA
H2511-00200-1/10W1-T
2
ea
R13, R14
RES, SMD, 0603, 20Ω,
1/10W, 1%, TF, ROHS
H2511-00R00-1/10W-T
1
ea
R11
H2511-01003-1/10W1-T
5
ea
R1, R3, R4, R6, R7 RES, SMD, 0603, 100k,
1/10W, 1%, TF, ROHS
H2511-02001-1/10W1-T
1
ea
R10
3
2N7002
2N7002LT1
PANASONIC
ERJ-3EKF20R0V
YAGEO
RC0603FR-0720RL
VENKEL
CR0603-10W-20R0FT
KOA
RK73H1JTTD2001F
VENKEL
CR0603-10W-2001FT
RESISTOR, SMD, 0603,
0Ω, 1/10W, TF, ROHS
RES, SMD, 0603, 2k,
1/10W, 1%, TF, ROHS
AN1492.2
February 14, 2014
Application Note 1492
TABLE 2. BILL OF MATERIALS (Continued)
PART NUMBER
H2511-02003-1/10W1-T
H2511-03163-1/10W1-T
QTY
UNIT
1
ea
1
ea
REFERENCE
DESIGNATOR
R5
R2
DESCRIPTION
RES, SMD, 0603, 200k,
1/10W, 1%, TF, ROHS
RES, SMD, 0603, 316k,
1/10W, 1%, TF, ROHS
MANUFACTURER
VENKEL
CR0603-10W-2003FT
YAGEO
RC0603FR-07200KL
VISHAY/DALE
CRCW0603200KFKEA
PANASONIC
ERJ-3EKF2003V
ROHM
MCR03EZPFX2003
PANASONIC
ERJ-3EKF3163V
VENKEL
CR0603-10W-3163FT
ROHM
MCR03EZPFX3163
YAGEO
RC0603FR-07316KL
VISHAY/DALE
CRCW0603316KFKEA
H2511-DNP
0
ea
R9
RES, SMD, 0603, DNPPLACE HOLDER, ROHS
GT11MSCBE-T
3
ea
S1 to S3
SWITCH-TOGGLE, SMD,
C&K COMPONENTS
ULTRAMINI, 1P, SPST MINI
4
MANUFACTURER
PART
GT11MSCKE
AN1492.2
February 14, 2014
Application Note 1492
ISL8088EVAL1Z Board Layout
FIGURE 1. TOP COMPONENTS
FIGURE 2. TOP LAYER ETCH
5
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February 14, 2014
Application Note 1492
ISL8088EVAL1Z Board Layout
(Continued)
FIGURE 3. 2ND LAYER ETCH
FIGURE 4. 3RD LAYER ETCH
6
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February 14, 2014
Application Note 1492
ISL8088EVAL1Z Board Layout
(Continued)
FIGURE 5. BOTTOM LAYER COMPONENTS (MIRRORS)
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
7
AN1492.2
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