Page 1
R2 R3
VOUT
VFB
----------------- -
1–
⎝⎠
⎛⎞
=
(EQ. 1)
Application Note 1492
Author: Huong Doan
ISL8088EVAL1Z REVA Dual 800mA Low Quiescent
Current 2.25MHz High Efficiency Synchronous Buck
Regulator
Description
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.
The ISL8088 is offered in a 3mmx3mm 10 Ld DFN package with
1mm maximum height. The complete converter occupies less
than 1.8cm
2
area.
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
•Soft-Stop Output Discharge During Disabled
• 30µA Quiescent Supply Current in PFM Mode
• Selectable Forced PWM Mode and PFM Mode
• 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.
• Over-Temperature Protection
• Independent Enable
Recommended Equipment
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
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
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 VIN and
negative return to PGND.
3. Verify that position is ON for SW2 and SW3.
4. Turn on the power supply.
5. Verify the output voltage is 2.5V for V
Evaluating the Other Output Voltage
The ISL8088EVAL1Z kit output is preset to 2.5V for V
1.8V for V
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:
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.
; however, output voltages can be adjusted from
OUT2
Mode Control
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 SE TTING S
SW2&3 ENABLE ON/OFF CONTROL
1OFFDisable V
3ONEnable V
SW1 SKIP FUNCTION
1 PWM Fixed PWM frequency at light load
3 PFM Force continuous mode
OUT
OUT
and 1.8V for V
OUT1
OUT1
OUT2.
and
Februar y 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
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
| Copyright Intersil Americas LLC 2009, 2010, 2014. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Page 2
Application Note 1492
2
AN1492.2
Februa ry 14, 2014
ISL8088EVAL1ZREVA Schematic
TU BUI / HUONG DOAN
OFF
ON/EX
PG
PWM
PFM
VOUT1
VOUT1_S
PGND
ON/EX
PGND
PGND
SYNC
PLEASE KEEP FB1, FB2 PINS TRACES SHORT
NOTE:
EN2
OFF
VOUT2_S
VOUT2
EN1
SGND
LX1_S
3/20/08
HUONG DOAN
VIN
100K
R3
PGND
VIN
VIN
1
VIN
C9
R11
R1
100K
SYNC
S1
VIN
VOUT1
VOUT1_S
C7
OPEN
R14
ISL8088IRZ
U1
PGND1
1
OPEN
2.2UH
VOUT1
C2
20
L1
10UF
C8
2
LX1
EN1
R4
100K
10PF
C5
10PF
C3
10UF
EN1
FB1
VOUT2
2.2UH
316K
2
EN2
LX2
FB2
C6
03/20/2008 HUONG DOAN
DUAL 800MA LOW IQ BUCK
ISL8088
2K
2N7002
EN2
C1
D2
2
1
Q2
32
R10
S2
2
3
S3
2
3
1
VOUT2_S
234
1
4
1
EN1
1
10
3
4
8
9
PGND2
3
LX1
1
432
1
3
2
OPEN
0
SYNC
SGND
EN2
OPEN
R7
VIN
100K
2
3
1
4
2
1
L2
LX2
OPEN
R9
PG
1
R2
100K
R6
200K
R5
10UF
C4
5
VOUT2
SYNC
R13
20
PG
11
6
72
UPDATED BY:
TITLE:
ENGINEER:
DATE:
DATE:
DATE:
DATE:
DRAWN BY:
RELEASED BY:
A
A
A
A
EN1
EP
PGND
LX1
VIN
FB1
LX2
PG
EN2
FB2
SYNCH
A
A
A
A
A
A
A
A
A
A
A
A A
NC
Page 3
Application Note 1492
TABLE 2. BILL OF MATERIALS
PART NUMBER QTY UNIT
ISL8088EVAL1ZREVAPCB 1 ea PWB-PCB,
H1045-00100-50V5-T 2 ea C3, C5 CAP, SMD, 0603, 10pF,
H1045-DNP 0 ea C9 CAP, SMD, 0603, DNP-
H1046-00106-6R3V10-T 3 ea C1, C2, C4 CAP, SMD, 0805, 10µF,
H1046-DNP 0 ea C6 to C8 CAP, SMD, 0805, DNP-
MDT2520-CR2R2M 2 ea L1, L2 COIL-PWR INDUCTOR,
1514-2 6 ea PGND, PGND1,
5000 4 ea EN1, EN2, PG,
5001 1 ea SGND CONN-MINI TEST PT,
LTST-C170CKT 1 ea D2 LED-GaAs RED, SMD,
ISL8088IRZ 1 ea U1 IC-DUAL SYNC. BUCK
2N7002-T 1 ea Q2 TRANSISTOR,
H2511-00200-1/10W1-T 2 ea R13, R14 RES, SMD, 0603, 20Ω,
H2511-00R00-1/10W-T 1 ea R11 RESISTOR, SMD, 0603,
H2511-01003-1/10W1-T 5 ea R1, R3, R4, R6, R7 RES, SMD, 0603, 100k,
H2511-02001-1/10W1-T 1 ea R10 RES, SMD, 0603, 2k,
REFERENCE
DESIGNATOR DESCRIPTION MANUFACTURER
ISL8088EVAL1Z,
REVA, ROHS
50V, 5%, COG, ROHS
PLACE HOLDER, ROHS
6.3V, 10%, X5R, ROHS
PLACE HOLDER, ROHS
SMD, 2520, 2.2µH, 20%,
1.35A, ROHS
CONN-TURRET, TERMINAL
PGND2, VIN,
VOUT1 ,VOUT2
SYNC
POST, TH, ROHS
CONN-MINI TEST PT,
VERTICAL, RED, ROHS
VERTICAL, BLK, ROHS
2mmx1.25mm, 100mW,
40mA, 10mcd, ROHS
REGULATOR, 10P, DFN,
3X3, ROHS
N-CHANNEL, 3LD, SOT-23,
60V, 115mA
1/10W, 1%, TF, ROHS
0Ω, 1/10W, TF, ROHS
1/10W, 1%, TF, ROHS
1/10W, 1%, TF, ROHS
MANUFACTURER
PART
TITAN ISL8088EVAL1ZREVAPCB
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
KEYSTONE 1514-2
KEYSTONE 5000
KEYSTONE 5001
LITEON/VISHAY LTST-C170CKT
ROHM SML-210LTT86
STANLEY ELEC. BR112H-TR
INTERSIL ISL8088IRZ
NAT’L SEMICNDTR 2N7002
MOTOROLA 2N7002LT1
PANASONIC ERJ-3EKF20R0V
YAGEO RC0603FR-0720RL
VENKEL CR0603-10W-20R0FT
KOA RK73H1JTTD2001F
VENKEL CR0603-10W-2001FT
3
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Page 4
Application Note 1492
TABLE 2. BILL OF MATERIALS (Continued)
REFERENCE
PART NUMBER QTY UNIT
H2511-02003-1/10W1-T 1 ea R5 RES, SMD, 0603, 200k,
H2511-03163-1/10W1-T 1 ea R2 RES, SMD, 0603, 316k,
H2511-DNP 0 ea R9 RES, SMD, 0603, DNP-
GT11MSCBE-T 3 ea S1 to S3 SWITCH-TOGGLE, SMD,
DESIGNATOR DESCRIPTION MANUFACTURER
1/10W, 1%, TF, ROHS
1/10W, 1%, TF, ROHS
PLACE HOLDER, ROHS
ULTRAMINI, 1P, SPST MINI
MANUFACTURER
PART
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
C&K COMPONENTS GT11MSCKE
4
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Page 5
Application Note 1492
ISL8088EVAL1Z Board Layout
FIGURE 1. TOP COMPONENTS
5
FIGURE 2. TOP LAYER ETCH
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Application Note 1492
ISL8088EVAL1Z Board Layout (Continued)
FIGURE 3. 2ND LAYER ETCH
6
FIGURE 4. 3RD LAYER ETCH
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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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