ISL8023AIRTAJZ [INTERSIL]

3A/4A Low Quiescent Current High Efficiency Synchronous Buck Regulator; 3A / 4A低静态电流高效率同步降压型稳压器
ISL8023AIRTAJZ
型号: ISL8023AIRTAJZ
厂家: Intersil    Intersil
描述:

3A/4A Low Quiescent Current High Efficiency Synchronous Buck Regulator
3A / 4A低静态电流高效率同步降压型稳压器

稳压器
文件: 总19页 (文件大小:622K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
3A/4A Low Quiescent Current High Efficiency  
Synchronous Buck Regulator  
ISL8023, ISL8024  
Features  
The ISL8023, ISL8024 is a high efficiency, monolithic,  
synchronous step-down DC/DC converter that can deliver up to  
3A/4A continuous output current from a 2.7V to 5.5V input  
supply. It uses current control architecture to deliver very low  
duty cycle operation at high frequency with fast transient  
response and excellent loop stability.  
• High Efficiency Synchronous Buck Regulator with up to 95%  
Efficiency  
• 0.8% Reference Accuracy Over-Temperature/Load/Line  
• Start-up with Pre-Biased Output  
• Internal Soft-Start - 1ms or Adjustable  
• Soft-Stop Output Discharge During Disabled  
The ISL8023, ISL8024 integrates a pair of low ON-resistance  
P-Channel and N-Channel internal MOSFETs to maximize  
efficiency and minimize external component count. The 100%  
duty-cycle operation allows less than 200mV dropout voltage  
at 4A output current. The operational frequency, pulse-width  
modulation (PWM), is adjustable from 500kHz to 4MHz.  
Connecting FS pin high sets the default frequency to 1MHz  
switching frequency allows the use of small external  
components. The ISL8023, ISL8024 can be configured for  
discontinuous or forced continuous operation at light load.  
Forced continuous operation reduces noise and RF  
• Adjustable Frequency from 500kHz to 4MHz - default at  
1MHz (8023/24), 2MHz (8023A/24A)  
• External Synchronization up to 4MHz  
• Negative OC protection  
• DC/DC POL Modules  
• µC/µP, FPGA and DSP Power  
• Plug-in DC/DC Modules for Routers and Switchers  
• Portable Instruments  
interference while discontinuous mode provides high  
efficiency by reducing switching losses at light loads.  
• Test and Measurement Systems  
• Li-ion Battery Powered Devices  
Fault protection is provided by internal hiccup mode current  
limiting during short circuit and overcurrent conditions, an  
output over voltage comparator and over-temperature monitor  
circuit. A power good output voltage monitor indicates when  
the output is in regulation.  
Applications  
• DC/DC POL Modules  
• µC/uP, FPGA and DSP Power  
• Plug-in DC/DC Modules for Routers and Switchers  
• Portable Instruments  
The ISL8023, ISL8024 offers a 1ms Power-Good (PG) timer at  
power-up. When in shutdown, ISL8023, ISL8024 discharges  
the output capacitor. Other features include internal fixed or  
adjustable soft-start, internal/external compensation, and  
thermal shutdown.  
• Test and Measurement Systems  
• Li-ion Battery Powered Devices  
The ISL8023, ISL8024 is offered in a space saving in a 16 Ld  
3x3 QFN lead free package with exposed pad lead frames for  
low thermal with 1mm maximum height. The complete  
Related Literature  
See AN1660, “3A/4A Low Quiescent Current High Efficiency  
Synchronous Buck Regulator”  
2
converter occupies less than 0.22 in area.  
Various fixed output voltage are available upon request. See  
ordering information for more detail.  
100  
90  
3.3V  
PFM  
OUT  
80  
70  
60  
50  
40  
3.3V  
PWM  
OUT  
0.0 0.5 1.0  
1.5 2.0  
2.5 3.0 3.5  
(A)  
4.0  
I
OUT  
FIGURE 1. EFFICIENCY T = +25°C V = 5V  
IN  
December 22, 2011  
FN7812.0  
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.  
1
ISL8023, ISL8024  
Pin Configuration  
ISL8023, ISL8024  
(16 LD TQFN)  
TOP VIEW  
16  
14  
15  
13  
VIN  
PGND  
PGND  
1
2
3
4
12  
11  
10  
9
VDD  
PG  
SGND  
FB  
SYNC  
7
8
6
5
Pin Descriptions  
PIN NUMBER  
SYMBOL  
DESCRIPTION  
1, 16  
VIN  
Input supply voltage. Connect two 22µF ceramic capacitors to power ground.  
Input supply voltage for the logic. Connect VIN PIN.  
2
3
VDD  
PG  
Power good is an open-drain output. Use 10kΩ to 100kΩ pull-up resistor connecting between VIN and  
PG. At power-up or EN HI, PG rising edge is delayed by 1ms upon output reached within regulation.  
4
Mode Selection pin. Connect to logic high or input voltage VIN for PWM mode. Connect to logic low or  
ground for PFM mode. Connect to an external function generator for synchronization with the positive  
edge trigger. There is an internal 1MW pull down resistor to prevent an undefined logic state in case  
of SYNIN pin float.  
SYNC  
5
6
EN  
FS  
Regulator enable pin. Enable the output when driven to high. Shut down the chip and discharge output  
capacitor when driven to low. There is an internal 1MW pull down resistor to prevent an undefined  
logic state in case of EN pin float.  
This pin sets the oscillator switching frequency, using a resistor, RFS, from the FS pin to GND. The  
frequency of operation may be programmed between 500kHz to 4MHz. The default frequency is 1MHz  
and configured for internal compensation if FS is connected to VIN.  
7
SS  
SS is used to adjust the soft start time. Set to SGND for internal 1ms rise time. Connect a capacitor from  
SS to SGND to adjust the soft start time. Do not use more than 33nF per IC.  
8, 9  
COMP, FB  
The feedback network of the regulator, VFB, is the negative input to the transconductance error  
amplifier. COMP is the output of the amplifier if FS resistor is used. Otherwise COMP is disconnected  
thru a MOSFET for internal compensation. Must connect COMP to SGND in internal compensation  
mode. The output voltage is set by an external resistor divider connected to VFB. With a properly  
selected divider, the output voltage can be set to any voltage between the power rail (reduced by  
converter losses) and the 0.6V reference. There is an internal compensation to meet a typical  
application. Additional external network across COMP and SGND might be required to improve the  
loop compensation of the amplifier operation.  
In addition, the regulator power-good and under-voltage protection circuitry use VFB to monitor the  
regulator output voltage  
10  
SGND  
PGND  
PHASE  
Signal ground.  
11, 12  
Power ground.  
13, 14, 15  
Exposed Pad  
Switching node connection. Connect to one terminal of the inductor.  
The exposed pad must be connected to the SGND pin for proper electrical performance. Place as  
much vias as possible under the pad connecting to SGND plane for optimal thermal performance.  
FN7812.0  
December 22, 2011  
2
ISL8023, ISL8024  
Ordering Information  
PART NUMBER  
(Notes 1, 2)  
PART  
MARKING  
OUTPUT VOLTAGE  
(V)  
TEMP. RANGE  
PACKAGE  
(Pb-Free)  
PKG.  
DWG. #  
(°C)  
ISL8023IRTAJZ  
023A  
024A  
23AA  
24AA  
ADJUSTABLE  
-40 to +85  
-40 to +85  
-40 to +85  
-40 to +85  
16 Ld 3x3 TQFN  
L16.3x3D  
L16.3x3D  
L16.3x3D  
L16.3x3D  
ISL8024IRTAJZ  
ISL8023AIRTAJZ  
ISL8024AIRTAJZ  
NOTES:  
ADJUSTABLE  
ADJUSTABLE  
ADJUSTABLE  
16 Ld 3x3 TQFN  
16 Ld 3x3 TQFN  
16 Ld 3x3 TQFN  
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 ISL8023, ISL8024. For more information on MSL please see techbrief  
TB363.  
Typical ApplicationBlock Diagram  
OUTPUT  
1.8V/4A  
L
1µH  
INPUT  
2.7V TO 5.5V  
VIN  
VDD  
EN  
PHASE  
PGND  
C2  
2 x 22µF  
C1  
22µF  
R2  
200k  
C3*  
4.7pF  
R1  
100k  
PG  
R3  
100k  
ISL8023, ISL8024  
SGND  
SYNC  
FS  
VFB  
COMP  
SS  
VIN  
SGND  
* C3 is optional. Recommend to  
put a placeholder for it. Check  
loop analysis first before use.  
FIGURE 2. TYPICAL APPLICATION DIAGRAM  
TABLE 1. COMPONENT SELECTION TABLE  
V
0.8V  
22µF  
1.2V  
22µF  
1.5V  
22µF  
1.8V  
22µF  
2.5V  
22µF  
3.3V  
3.6  
OUT  
C1  
C2  
C3  
L1  
R2  
R3  
22µF  
2 x 22µF  
4.7pF  
22µF  
2 x 22µF  
4.7pF  
4X22µF  
4.7pF  
2 x 22µF  
4.7pF  
2 x 22µF  
4.7pF  
2 x 22µF  
4.7pF  
2 x 22µF  
4.7pF  
0.47~1µH  
33k  
0.47~1µH  
100k  
0.47~1µH  
150k  
0.68~1.5µH  
200k  
0.68~1.5µH  
316k  
1~2.2µH  
450k  
1~2.2µH  
500k  
100k  
100k  
100k  
100k  
100k  
100k  
100k  
FN7812.0  
December 22, 2011  
3
ISL8023, ISL8024  
COMP  
55pF  
FS  
SYNC  
SS  
EN  
SOFT
START  
SHUTDOWN  
VDD  
SHUTDOWN  
BANDGAP  
100k  
+
+
VIN  
OSCILLATOR  
VREF  
3pF  
+
EAMP  
COMP  
P
-
-
PWM/PFM  
LOGIC  
CONTROLLER  
PROTECTION  
HS DRIVER  
PHASE  
PGND  
LS  
DRIVER  
N
+
VFB  
SLOPE
COMP  
6k  
+
0.6V  
-
CSA  
-
+
-
OV  
+
OCP  
-
0.85*VREF  
ISET  
THRESHOLD  
+
UV  
+
SKIP  
-
PG  
1ms  
DELAY  
NEG CURRENT  
SENSING  
SGND  
ZERO-CROSS  
SENSING  
-
SCP  
+
0.5V  
100  
SHUTDOWN  
FIGURE 3. FUNCTIONAL BLOCK DIAGRAM  
FN7812.0  
December 22, 2011  
4
ISL8023, ISL8024  
Absolute Maximum Ratings (Reference to GND)  
Thermal Information  
VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V  
EN, FS, PG, SYNC, VFB . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to VIN + 0.3V  
PHASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -3V (100ns)/(DC) to 6.5V (DC)  
COMP, SS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 2.7V  
Thermal Resistance  
θ
(°C/W)  
45  
θ
(°C/W)  
6.5  
JA  
JC  
16 LD TQFN Package (Notes 4, 5) . . . . .  
Junction Temperature Range . . . . . . . . . . . . . . . . . . . . . . .-55°C to +125°C  
Storage Temperature Range. . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C  
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below  
http://www.intersil.com/pbfree/Pb-FreeReflow.asp  
Recommended Operating Conditions  
VIN Supply Voltage Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7V to 5.5V  
Load Current Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0A to 4A  
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C  
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product  
reliability and result in failures not covered by warranty.  
NOTES:  
4. θ is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech  
JA  
Brief TB379.  
5. θ , “case temperature” location is at the center of the exposed metal pad on the package underside.  
JC  
Electrical Specifications Unless otherwise noted, all parameter limits are established over the recommended operating  
conditions and the typical specification are measured at the following conditions: T = -40°C to +85°C, V = 3.6V, EN = V , unless otherwise  
A
IN  
IN  
noted. Typical values are at T = +25°C. Boldface limits apply over the operating temperature range, -40°C to +85°C  
A
MIN  
MAX  
PARAMETER  
SYMBOL  
TEST CONDITIONS  
(Note 6)  
2.2  
TYP  
(Note 6)  
UNITS  
INPUT SUPPLY  
Undervoltage Lockout Threshold  
V
V
Rising, no load  
2.5  
2.4  
50  
2.7  
V
V
IN  
UVLO  
Falling, no load  
Quiescent Supply Current  
I
SYNC = GND, no load at the output  
µA  
µA  
VIN  
SYNC = GND, no load at the output and no  
switches switching  
50  
60  
SYNC = VIN, F = 1MHz, no load at the output  
8
5
15  
7
mA  
µA  
S
Shut Down Supply Current  
I
SYNC = GND, V = 5.5V, EN = low  
IN  
SD  
OUTPUT REGULATION  
Reference Voltage - ISL8023IRZ, ISL8024IRZ  
VFB Bias Current - ISL8023IRZ, ISL8024IRZ  
Line Regulation  
V
0.595  
0.600  
0.1  
0.2  
1
0.605  
V
REF  
I
VFB = 0.75V  
µA  
VFB  
V
= V + 0.5V to 5.5V (minimal 2.7V)  
%/V  
ms  
µA  
IN  
SS = SGND  
= 0.1V  
O
Soft-Start Ramp Time Cycle  
Soft-Start Charging Current  
OVERCURRENT PROTECTION  
Current Limit Blanking Time  
I
V
1.2  
1.6  
2.0  
SS  
SS  
t
17  
Clock  
OCON  
pulses  
Overcurrent and Auto Restart Period  
Positive Peak Current Limit  
t
8
SS cycle  
OCOFF  
I
4A application  
5.2  
3.9  
6.5  
4.8  
1.2  
0.9  
7.8  
5.9  
A
A
PLIMIT  
3A application  
Peak Skip Limit  
I
4A application (test at 3.6V)  
3A application (test at 3.6V)  
0.9  
1.5  
A
SKIP  
0.65  
-200  
-3.0  
1.15  
200  
-1.8  
A
Zero Cross Threshold  
Negative Current Limit  
mA  
A
I
-2.4  
NLIMIT  
FN7812.0  
December 22, 2011  
5
ISL8023, ISL8024  
Electrical Specifications Unless otherwise noted, all parameter limits are established over the recommended operating  
conditions and the typical specification are measured at the following conditions: T = -40°C to +85°C, V = 3.6V, EN = V , unless otherwise  
A
IN  
IN  
noted. Typical values are at T = +25°C. Boldface limits apply over the operating temperature range, -40°C to +85°C (Continued)  
A
MIN  
MAX  
PARAMETER  
COMPENSATION  
SYMBOL  
TEST CONDITIONS  
(Note 6)  
TYP  
(Note 6)  
UNITS  
Error Amplifier Trans-Conductance  
FS = VIN  
FS with Resistor  
80  
150  
0.2  
µA/V  
µA/V  
Ω
Trans-Resistance  
RT  
0.15  
0.25  
PHASE  
P-Channel MOSFET ON-Resistance  
V
V
V
V
= 5V, I = 200mA  
35  
50  
12  
20  
45  
70  
55  
90  
25  
37  
mΩ  
mΩ  
mΩ  
mΩ  
%
IN  
IN  
IN  
IN  
O
= 2.7V, I = 200mA  
O
N-Channel MOSFET ON-Resistance  
= 5V, I = 200mA  
19  
O
= 2.7V, I = 200mA  
28  
O
PHASE Maximum Duty Cycle  
PHASE Minimum On-Time  
OSCILLATOR  
100  
SYNC = High  
140  
ns  
Nominal Switching Frequency  
Fsw  
FS = VIN  
800  
1000  
490  
1200  
kHz  
kHz  
kHz  
V
FS with RS = 402kΩ  
FS with RS = 42.2kΩ  
4200  
0.75  
0.15  
3.6  
SYNC Logic Low to High Transition Range  
SYNC Hysteresis  
0.70  
0.80  
5
V
SYNC Logic Input Leakage Current  
PG  
V
= 3.6V  
µA  
IN  
Output Low Voltage  
0.3  
2
V
ms  
µA  
V
Delay Time (Rising Edge)  
PG Pin Leakage Current  
OVP PG Rising Threshold  
UVP PG Rising Threshold  
UVP PG Hysteresis  
0.5  
80  
1
0.01  
0.80  
85  
0.1  
90  
%
5
%
PGOOD Delay Time (Falling Edge)  
EN  
15  
µs  
Logic Input Low  
0.4  
1
V
Logic Input High  
0.9  
V
EN Logic Input Leakage Current  
Thermal Shutdown  
0.1  
150  
25  
µA  
°C  
°C  
Thermal Shutdown Hysteresis  
NOTE:  
6. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design  
FN7812.0  
December 22, 2011  
6
ISL8023, ISL8024  
Typical Operating Performance Unless otherwise noted, operating conditions are: T = +25°C, V = 5V,  
A
VIN  
EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I  
= 0A to 4A).  
IN  
IN  
1
2
OUT  
100  
100  
90  
80  
70  
60  
50  
40  
90  
80  
70  
60  
50  
40  
1.2V  
1.2V  
OUT  
1.5V  
OUT  
1.5V  
OUT  
OUT  
1.8V  
OUT  
1.8V  
OUT  
2.5V  
2.5V  
OUT  
OUT  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
I
I
OUT  
OUT  
FIGURE 4. EFFICIENCY vs LOAD (1MHz 3.3 V PWM)  
IN  
FIGURE 5. EFFICIENCY vs LOAD (1MHz 3.3 V PFM)  
IN  
100  
100  
90  
80  
70  
60  
50  
40  
90  
80  
70  
60  
50  
40  
1.5V  
OUT  
1.2V  
1.8V  
OUT  
1.5V  
OUT  
OUT  
1.8V  
OUT  
2.5V  
2.5V  
OUT  
1.2V  
OUT  
OUT  
3.3V  
OUT  
3.3V  
OUT  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
I
OUT  
I
OUT  
FIGURE 6. EFFICIENCY vs LOAD (1MHz 5V PWM)  
IN  
FIGURE 7. EFFICIENCY vs LOAD (1MHz 5V PFM  
IN  
)
1.08  
0.90  
0.72  
0.54  
0.36  
0.18  
0
1.244  
1.238  
1.232  
1.226  
1.220  
1.214  
1.208  
3.3V PWM MODE  
IN  
3.3V PFM MODE  
IN  
5V PWM MODE  
IN  
5V PFM MODE  
IN  
3.3V PWM MODE  
IN  
5V PWM MODE  
IN  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
0.0  
0.5  
1.0  
1.5  
I
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
I
OUT  
OUT  
FIGURE 8. POWER DISSIPATION vs LOAD (1MHz, V  
= 1.8V)  
FIGURE 9. V  
REGULATION vs LOAD (1MHz, V  
= 1.2V)  
OUT  
OUT  
OUT  
FN7812.0  
December 22, 2011  
7
ISL8023, ISL8024  
Typical Operating Performance Unless otherwise noted, operating conditions are: T = +25°C, V = 5V,  
A
VIN  
EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I  
= 0A to 4A). (Continued)  
IN  
IN  
1
2
OUT  
1.529  
1.830  
3.3V PFM MODE  
IN  
1.524  
1.519  
1.514  
1.509  
1.504  
1.499  
1.824  
1.818  
1.812  
1.806  
1.800  
5V PFM MODE  
IN  
3.3V PFM MODE  
IN  
5V PFM MODE  
IN  
3.3V PWM MODE  
IN  
3.3V PWM MODE  
IN  
5V PWM MODE  
IN  
5V PWM MODE  
IN  
1.794  
0.0  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
I
I
OUT  
OUT  
FIGURE 11. V  
REGULATION vs LOAD (1MHz, V  
= 1.8V)  
OUT  
FIGURE 10. V  
REGULATION vs LOAD (1MHz, V  
= 1.5V)  
OUT  
OUT  
OUT  
2.540  
2.532  
2.524  
2.516  
2.508  
2.500  
3.354  
3.345  
3.336  
3.327  
3.318  
3.309  
3.3V PFM MODE  
IN  
5V PFM MODE  
IN  
5V PFM MODE  
IN  
3.3V PWM MODE  
IN  
5V PWM MODE  
IN  
5V PWM MODE  
IN  
2.492  
3.300  
0.0  
0.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
0.5  
1.0  
1.5  
2.0  
(A)  
2.5  
3.0  
3.5  
4.0  
I
I
OUT  
OUT  
FIGURE 12. V  
REGULATION vs LOAD (1MHz, V  
= 2.5V)  
OUT  
FIGURE 13. V  
REGULATION vs LOAD (1MHz, V  
= 3.3V)  
OUT  
OUT  
OUT  
1.815  
1.810  
1.805  
1.800  
1.795  
1.790  
1.785  
1.836  
1.828  
1.820  
1.812  
1.804  
1.796  
1.788  
0A LOAD  
0A LOAD  
2A LOAD  
4A LOAD  
2A LOAD  
4A LOAD  
2.0  
2.5  
3.0  
3.5  
4.0  
(V)  
4.5  
5.0  
5.5  
6.0  
2.0  
2.5  
3.0  
3.5  
4.0  
(V)  
4.5  
5.0  
5.5  
6.0  
V
V
IN  
IN  
FIGURE 15. OUTPUT VOLTAGE REGULATION vs V  
FIGURE 14. OUTPUT VOLTAGE REGULATION vs V  
IN  
IN  
(PFM V  
= 1.8V)  
(PWM V  
= 1.8 )  
OUT  
OUT  
FN7812.0  
December 22, 2011  
8
ISL8023, ISL8024  
Typical Operating Performance Unless otherwise noted, operating conditions are: T = +25°C, V = 5V,  
A
VIN  
EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I = 0A to 4A). (Continued)  
OUT  
IN  
IN  
1
2
PHASE 2V/Div  
PHASE 2V/Div  
V
RIPPLE 20mV/Div  
V
L
RIPPLE 20mV/Div  
OUT  
OUT  
I
1A/Div  
L
I
1A/Div  
FIGURE 16. STEADY STATE OPERATION AT NO LOAD (PWM)  
FIGURE 17. STEADY STATE OPERATION AT NO LOAD (PFM)  
V
RIPPLE 50mV/Div  
OUT  
PHASE 2V/Div  
I
2A/Div  
L
I
2A/Div  
L
V
RIPPLE 20mV/Div  
OUT  
FIGURE 18. STEADY STATE OPERATION WITH FULL LOAD  
FIGURE 19. LOAD TRANSIENT (PWM)  
V
RIPPLE 50mV/Div  
OUT  
EN 2V/Div  
V
1V/Div  
OUT  
I
1A/Div  
L
I
2A/Div  
L
PG 5V/Div  
FIGURE 21. SOFT-START WITH NO LOAD (PWM)  
FIGURE 20. LOAD TRANSIENT (PFM)  
FN7812.0  
December 22, 2011  
9
ISL8023, ISL8024  
Typical Operating Performance Unless otherwise noted, operating conditions are: T = +25°C, V = 5V,  
A
VIN  
EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I = 0A to 4A). (Continued)  
OUT  
IN  
IN  
1
2
EN 2V/Div  
EN 2V/Div  
V
1V/Div  
OUT  
V
1V/Div  
OUT  
I
1A/Div  
I
1A/Div  
L
L
PG 2V/Div  
PG 5V/Div  
FIGURE 22. SOFT-START AT NO LOAD (PFM)  
FIGURE 23. SOFT-START WITH PRE-BIASED 1V  
EN 2V/Div  
EN 2V/Div  
V
1V/Div  
OUT  
V
1V/Div  
OUT  
I
1A/Div  
L
I
2A/Div  
L
PG 5V/Div  
PG 5V/Div  
FIGURE 25. SOFT-DISCHARGE SHUTDOWN  
FIGURE 24. SOFT-START AT FULL LOAD  
PHASE 5V/Div  
PHASE 5V/Div  
V
RIPPLE 20mV/Div  
V
RIPPLE 20mV/Div  
OUT  
OUT  
I
0.5A/Div  
L
I
2A/Div  
L
SYNC 5V/Div  
SYNC 5V/Div  
FIGURE 26. STEADY STATE OPERATION AT NO LOAD WITH  
FREQUENCY = 2MHz  
FIGURE 27. STEADY STATE OPERATION AT FULL LOAD WITH  
FREQUENCY = 2MHz  
FN7812.0  
December 22, 2011  
10  
ISL8023, ISL8024  
Typical Operating Performance Unless otherwise noted, operating conditions are: T = +25°C, V = 5V,  
A
VIN  
EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I = 0A to 4A). (Continued)  
OUT  
IN  
IN  
1
2
PHASE 5V/Div  
PHASE 5V/Div  
V
RIPPLE 20mV/Div  
V
RIPPLE 20mV/Div  
OUT  
OUT  
I
1A/Div  
L
I
0.2A/Div  
L
SYNC 5V/Div  
SYNC 5V/Div  
FIGURE 29. STEADY STATE OPERATION AT FULL LOAD (PWM) WITH  
FREQUENCY = 4MHz  
FIGURE 28. STEADY STATE OPERATION AT NO LOAD WITH  
FREQUENCY = 4MHz  
PHASE 5V/Div  
PHASE 5V/Div  
I
2A/Div  
L
V
1V/Div  
2A/Div  
OUT  
V
1V/Div  
OUT  
I
L
SYNC 5V/Div  
SYNC 5V/Div  
FIGURE 30. OUTPUT SHORT CIRCUIT  
FIGURE 31. OUTPUT SHORT CIRCUIT RECOVERY  
Typical Operating Performance for A Part Unless otherwise noted, operating conditions are:  
T
= +25°C, V  
= 5V, EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I  
= 0A to 4A).  
OUT  
A
VIN  
IN  
IN  
1
2
PHASE 2V/Div  
PHASE 2V/Div  
V
RIPPLE 20mV/Div  
V
L
RIPPLE 20mV/Div  
OUT  
OUT  
I
0.5A/Div  
L
I
1A/Div  
FIGURE 32. STEADY STATE OPERATION AT NO LOAD (PWM)  
FIGURE 33. STEADY STATE OPERATION AT NO LOAD (PFM)  
FN7812.0  
December 22, 2011  
11  
ISL8023, ISL8024  
Typical Operating Performance for A Part Unless otherwise noted, operating conditions are:  
T
= +25°C, V  
= 5V, EN = V , SYNC = V , L = 1.0µH, C = 22µF, C = 2 x 22µF, I  
= 0A to 4A). (Continued)  
OUT  
A
VIN  
IN  
IN  
1
2
EN 2V/Div  
PHASE 2V/Div  
V
1V/Div  
OUT  
I
2A/Div  
L
I
1A/Div  
V
RIPPLE 20mV/Div  
L
OUT  
PG 5V/Div  
FIGURE 35. SOFT-START WITH NO LOAD (PWM)  
FIGURE 34. STEADY STATE OPERATION WITH FULL LOAD  
EN 2V/Div  
EN 2V/Div  
V
1V/Div  
V
1V/Div  
OUT  
OUT  
I
1A/Div  
L
I
1A/Div  
L
PG 5V/Div  
PG 5V/Div  
FIGURE 36. SOFT-START AT NO LOAD (PFM)  
FIGURE 37. SOFT-START AT FULL LOAD  
EN 2V/Div  
V
1V/Div  
OUT  
I
1A/Div  
L
PG 5V/Div  
FIGURE 38. SOFT-DISCHARGE SHUTDOWN  
FN7812.0  
December 22, 2011  
12  
ISL8023, ISL8024  
Theory of Operation  
V
EAMP  
The ISL8023, ISL8024 is a step-down switching regulator optimized  
for battery-powered handheld applications. The regulator operates  
at 1MHz fixed default switching frequency, when FS is connected to  
VIN, under heavy load conditions to allow smaller external inductors  
and capacitors to be used for minimal printed-circuit board (PCB)  
area. By connecting a resistor from FS to SGND, the operational  
frequency adjustable range is 500kHz to 4MHz. At light load, the  
regulator reduces the switching frequency, unless forced to the fixed  
frequency, to minimize the switching loss and to maximize the  
battery life. The quiescent current when the output is not loaded is  
typically only 45µA. The supply current is typically only 5µA when  
the regulator is shut down.  
V
CSA  
DUTY  
CYCLE  
I
L
V
OUT  
FIGURE 39. PWM OPERATION WAVEFORMS  
PWM Control Scheme  
SKIP Mode  
Pulling the SYNC pin HI (>0.8V) forces the converter into PWM  
mode, regardless of output current. The ISL8023, ISL8024 employs  
the current-mode pulse-width modulation (PWM) control scheme for  
fast transient response and pulse-by-pulse current limiting. Figure 3  
on page 4 shows the Functional Block Diagram. The current loop  
consists of the oscillator, the PWM comparator, current sensing  
circuit and the slope compensation for the current loop stability. The  
slope compensation is 440mV/Ts, which changed with frequency.  
The gain for the current sensing circuit is typically 200mV/A. The  
control reference for the current loops comes from the error  
amplifier's (EAMP) output.  
Pulling the SYNC pin LO (<0.4V) forces the converter into PFM  
mode. The ISL8023, ISL8024 enters a pulse-skipping mode at  
light load to minimize the switching loss by reducing the  
switching frequency. Figure 40 illustrates the skip-mode  
operation. A zero-cross sensing circuit shown in Figure 4 on  
page 7monitors the N-FET current for zero crossing. When 8  
consecutive cycles of the inductor current crossing zero are  
detected, the regulator enters the skip mode. During the eight  
detecting cycles, the current in the inductor is allowed to become  
negative. The counter is reset to zero when the current in any  
cycle does not cross zero.  
The PWM operation is initialized by the clock from the oscillator.  
The P-Channel MOSFET is turned on at the beginning of a PWM  
cycle and the current in the MOSFET starts to ramp up. When the  
sum of the current amplifier CSA and the slope compensation  
reaches the control reference of the current loop, the PWM  
comparator COMP sends a signal to the PWM logic to turn off the  
P-FET and turn on the N-Channel MOSFET. The N-FET stays on until  
the end of the PWM cycle. Figure 39 shows the typical operating  
waveforms during the PWM operation. The dotted lines illustrate  
the sum of the slope compensation ramp and the current-sense  
amplifier’s CSA output.  
Once the skip mode is entered, the pulse modulation starts being  
controlled by the SKIP comparator shown in Figure 4 on page 7.  
Each pulse cycle is still synchronized by the PWM clock. The  
P-FET is turned on at the clock's rising edge and turned off when  
the output is higher than 1.5% of the nominal regulation or when  
its current reaches the peak Skip current limit value. Then the  
inductor current is discharging to 0A and stays at zero. The  
internal clock is disabled. The output voltage reduces gradually  
due to the load current discharging the output capacitor. When  
the output voltage drops to the nominal voltage, the P-FET will be  
turned on again at the rising edge of the internal clock as it  
repeats the previous operations.  
The output voltage is regulated by controlling the V  
EAMP  
voltage  
to the current loop. The bandgap circuit outputs a 0.6V reference  
voltage to the voltage loop. The feedback signal comes from the  
VFB pin. The soft-start block only affects the operation during the  
start-up and will be discussed separately. The error amplifier is a  
transconductance amplifier that converts the voltage error signal  
to a current output. The voltage loop is internally compensated  
with the 55pF and 100kΩ RC network. The maximum EAMP  
voltage output is precisely clamped to 1.6V.  
The regulator resumes normal PWM mode operation when the  
output voltage drops 1.5% below the nominal voltage.  
FN7812.0  
December 22, 2011  
13  
ISL8023, ISL8024  
PWM  
PFM  
PWM  
CLOCK  
8 CYCLES  
PFM CURRENT LIMIT  
LOAD CURRENT  
I
L
0
NOMINAL +1.5%  
V
OUT  
NOMINAL -1.5%  
NOMINAL  
FIGURE 40. SKIP MODE OPERATION WAVEFORMS  
soft-start is attempted again. If the overcurrent condition goes  
away during the delay of four soft-start periods, the output will  
resume back into regulation point after hiccup mode expires.  
Frequency Adjust  
The frequency of operation is fixed at 1MHz and internal  
compensation when FS is tied to VIN. Adjustable frequency range  
from 500kHz to 4MHz via simple resistor connecting FS to SGND  
according to Equation 1:  
Negative current Protection  
Similar to the overcurrent, the negative current protection is  
realized by monitoring the current across the low-side N-FET, as  
shown in Figure 4 on page 7. When the valley point of the inductor  
current reached -3A for 4 consecutive cycles, both P-FET and N-FET  
are off. The 100Ω in parallel to the N-FET will activate discharging  
the output into regulation. The control will begin to switch when  
output is within regulation. The regulator will be in PFM for 20µs  
before switching to PWM if necessary.  
3
220 10  
------------------------------  
R [kΩ] =  
14  
T
f
[kHz]  
OSC  
(EQ. 1)  
Overcurrent Protection  
The overcurrent protection is realized by monitoring the CSA  
output with the OCP comparator, as shown in Figure 4. The current  
sensing circuit has a gain of 200mV/A, from the P-FET current to  
the CSA output. When the CSA output reaches the threshold, the  
OCP comparator is trippled to turn off the P-FET immediately. The  
overcurrent function protects the switching converter from a  
shorted output by monitoring the current flowing through the  
upper MOSFET.  
PG  
PG is an open-drain output of a window comparator that  
continuously monitors the buck regulator output voltage. PG is  
actively held low when EN is low and during the buck regulator  
soft-start period. After 1ms delay of the soft-start period, PG  
becomes high impedance as long as the output voltage is within  
nominal regulation voltage set by VFB. When VFB drops 15% below  
or raises 0.6V above the nominal regulation voltage, the ISL8023,  
ISL8024 pulls PG low. Any fault condition forces PG low until the  
fault condition is cleared by attempts to soft-start. For logic level  
Upon detection of overcurrent condition, the upper MOSFET will  
be immediately turned off and will not be turned on again until  
the next switching cycle. Upon detection of the initial overcurrent  
condition, the overcurrent fault counter is set to 1. If, on the  
subsequent cycle, another overcurrent condition is detected, the  
OC fault counter will be incremented. If there are 17 sequential  
OC fault detections, the regulator will be shut down under an  
overcurrent fault condition. An overcurrent fault condition will  
result in the regulator attempting to restart in a hiccup mode  
within the delay of eighth soft-start periods. At the end of the  
eight soft-start wait period, the fault counters are reset and  
output voltages, connect an external pull-up resistor, R , between  
1
PG and VIN. A 100kΩ resistor works well in most applications.  
UVLO  
When the input voltage is below the undervoltage lock-out (UVLO)  
threshold, the regulator is disabled.  
FN7812.0  
December 22, 2011  
14  
ISL8023, ISL8024  
lower inductor value can be used to optimize the total converter  
Soft Start-Up  
system performance. For example, for higher output voltage 3.3V  
application, in order to decrease the inductor current ripple and  
output voltage ripple, the output inductor value can be increased.  
It is recommended to set the ripple inductor current  
approximately 30% of the maximum output current for optimized  
performance. The inductor ripple current can be expressed as  
shown in Equation 3:  
The soft-start-up reduces the in-rush current during the start-up.  
The soft-start block outputs a ramp reference to the input of the  
error amplifier. This voltage ramp limits the inductor current as  
well as the output voltage speed so that the output voltage rises  
in a controlled fashion. When VFB is less than 0.1V at the  
beginning of the soft-start, the switching frequency is reduced to  
200kHz so that the output can start-up smoothly at light load  
condition. During soft-start, the IC operates in the SKIP mode to  
support pre-biased output condition.  
V
O
--------  
V
1 –  
(EQ. 3)  
O
V
IN  
-----------------------------------  
ΔI =  
L f  
S
Tie SS to SGND for internal soft start approximately 1ms.  
Connect a capacitor from SS to SGND to adjust the soft start  
time. This capacitor, along with an internal 1.6µA current source  
sets the soft-start interval of the converter, T as shown by  
Equation 2.  
The inductor’s saturation current rating needs to be at least  
larger than the peak current. The ISL8023, ISL8024 protects the  
typical peak current 6A. The saturation current needs be over 7A  
for maximum output current application.  
SS  
C
F] = 3.33 T [s]  
SS  
(EQ. 2)  
SS  
ISL8023, ISL8024 uses internal compensation network and the  
output capacitor value is dependent on the output voltage. The  
ceramic capacitor is recommended to be X5R or X7R. The  
recommended X5R or X7R minimum output capacitor values are  
shown in Table 1.  
C
must be less than 33nF to insure proper soft-start reset after  
ss  
fault condition.  
Enable  
In Table 1, the minimum output capacitor value is given for the  
different output voltage to make sure that the whole converter  
system is stable. Additional output capacitance should be added  
for better performances in applications where high load transient  
or low output ripple is required. It is recommended to check the  
system level performance along with the simulation model.  
The enable (EN) input allows the user to control the turning on or  
off the regulator for purposes such as power-up sequencing.  
When the regulator is enabled, there is typically a 600µs delay  
for waking up the bandgap reference and then the soft-start-up  
begins.  
Discharge Mode (Soft-Stop)  
When a transition to shutdown mode occurs or the VIN UVLO is  
set, the outputs discharge to GND through an internal 100Ω  
switch.  
Output Voltage Selection  
The output voltage of the regulator can be programmed via an  
external resistor divider that is used to scale the output voltage  
relative to the internal reference voltage and feed it back to the  
inverting input of the error amplifier. Refer to Figure 2.  
Power MOSFETs  
The output voltage programming resistor, R , will depend on the  
2
The power MOSFETs are optimized for best efficiency. The  
ON-resistance for the P-FET is typically 40mΩ and the  
ON-resistance for the N-FET is typically 30mΩ.  
value chosen for the feedback resistor and the desired output  
voltage of the regulator. The value for the feedback resistor is  
typically between 10kΩ and 100kΩ, as shown in Equation 4.  
100% Duty Cycle  
V
O
(EQ. 4)  
----------  
R
= R  
1  
2
3
VFB  
The ISL8023, ISL8024 features 100% duty cycle operation to  
maximize the battery life. When the battery voltage drops to a  
level that the ISL8023, ISL8024 can no longer maintain the  
regulation at the output, the regulator completely turns on the  
P-FET. The maximum dropout voltage under the 100% duty-cycle  
operation is the product of the load current and the  
ON-resistance of the P-FET.  
If the output voltage desired is 0.6V, then R is left unpopulated  
and R is shorted. There is a leakage current from VIN to PHASE.  
It is recommended to preload the output with 10µA minimum.  
For better performance, add 15pF in parallel with R (100kΩ).  
3
2
2
Check loop analysis before use in application.  
VSET marginally adjust VFB according to the “Electrical  
Specifications” table on page 5.  
Thermal Shut-Down  
The ISL8023, ISL8024 has built-in thermal protection. When the  
internal temperature reaches +150°C, the regulator is completely  
shut down. As the temperature drops to +125°C, the ISL8023,  
ISL8024 resumes operation by stepping through the soft-start.  
Input Capacitor Selection  
The main functions for the input capacitor are to provide  
decoupling of the parasitic inductance and to provide filtering  
function to prevent the switching current flowing back to the  
battery rail. At least two 22µF X5R or X7R ceramic capacitors are  
a good starting point for the input capacitor selection.  
Applications Information  
Output Inductor and Capacitor Selection  
To consider steady state and transient operations, ISL8023,  
ISL8024 typically uses a 1.0µH output inductor. The higher or  
FN7812.0  
December 22, 2011  
15  
ISL8023, ISL8024  
Loop Compensation Design  
Power Stage Transfer Functions  
When there is an external resistor connected from FS to SGND,  
COMP pin is active for external loop compensation. The ISL8023,  
ISL8024 uses constant frequency peak current mode control  
architecture to achieve fast loop transient response. An accurate  
current sensing pilot device in parallel with the upper MOSFET is  
used for peak current control signal and overcurrent protection.  
The inductor is not considered as a state variable since its peak  
current is constant, and the system becomes single order  
system. It is much easier to design a type II compensator to  
stabilize the loop than to implement voltage mode control. Peak  
current mode control has inherent input voltage feed-forward  
function to achieve good line regulation. Figure 39 shows the  
small signal model of the synchronous buck regulator.  
Transfer function F (S) from control to output voltage is:  
1
S
-----------  
1 +  
ˆ
ω
v
esr  
o
(EQ. 8)  
-----  
ˆ
--------------------------------------  
F (S) =  
= V  
1
in  
2
d
S
S
------ -------------  
+
+ 1  
2
ω Q  
o
p
ω
o
C
1
1
o
------------  
----------------  
ω
=
,Q R ----- ,ω =  
Where,  
esr  
p
o
o
R C  
L
L C  
c
o
P
P
o
Transfer function F (S) from control to inductor current is given  
2
by Equation 9:  
S
-----  
1 +  
ˆ
V
ω
I
(EQ. 9)  
o
in  
z
----  
ˆ
---------------------- --------------------------------------  
F (S) =  
=
=
2
2
R
+ R  
LP  
d
o
S
S
------ -------------  
+
+ 1  
^
^
^
2
L
R
ω Q  
i
P
LP  
i
L
v
o
p
in  
ω
o
o
^
d
V
in  
^
^
1:D  
1
I d  
V
L
in  
-------------  
ω
where  
.
z
R C  
Rc  
Co  
o
o
+
R
T
Current loop gain T (S) is expressed as Equation 10:  
i
Ro  
(EQ. 10)  
T (S) = R F F (S)H (S)  
i
t
m
2
e
T (S)  
i
The voltage loop gain with open current loop is Equation 11:  
^
d
K
T (S) = KF F (S)A (S)  
Fm  
(EQ. 11)  
v
m
1
v
The Voltage loop gain with current loop closed is given by  
Equation 12:  
T (S)  
+
v
He(S)  
^
v
comp  
T (S)  
-Av(S)  
v
(EQ. 12)  
----------------------  
L (S) =  
v
1 + T (S)  
i
FIGURE 41. SMALL SIGNAL MODEL OF SYNCHRONOUS BUCK  
REGULATOR  
V
FB  
---------  
K =  
, V  
FB  
Where,  
is the feedback voltage of the voltage  
V
error amplifiero. If T (S)>>1, then Equation 12 can be simplified as  
i
PWM Comparator Gain F :  
m
Equation 13:  
S
The PWM comparator gain Fm for peak current mode control is  
-----------  
1 +  
given by Equation 5:  
V
R
+ R  
ω
A (S)  
1
R C  
o o  
FB  
o
LP  
esr v  
--------- ---------------------- -----------------------------------  
-------------  
(EQ. 13)  
L (S)=  
, ω  
p
v
V
R
S
H (S)  
ˆ
o
t
e
d
1
(EQ. 5)  
------  
1 +  
----------------  
-----------------------------  
F
=
=
ω
m
ˆ
p
(S + S )T  
s
v
comp  
e
n
Where, S is the slew rate of the slope compensation and S is  
given by Equation 6  
Equation 13 shows that the system is a single order system,  
e
n
ω
p
which has a single pole located at  
before the half switching  
frequency. Therefore, a simple type II compensator can be easily  
used to stabilize the system.  
V
V  
o
L
P
(EQ. 6)  
in  
-------------------  
S
= R  
n
t
where, R is trans-resistance, which is the gain of the current  
t
amplifier.  
CURRENT SAMPLING TRANSFER FUNCTION H (S):  
e
In current loop, the current signal is sampled every switching  
cycle. It has the following transfer function in Equation 7:  
2
(EQ. 7)  
S
S
------ -------------  
+
H (S)=  
+ 1  
e
2
n
ω Q  
n
n
ω
2
π
--  
Q
= – , ω = πf  
n
n
s
where, Q and ω are given by  
n
n
FN7812.0  
December 22, 2011  
16  
ISL8023, ISL8024  
where, GM is the sum of the trans-conductance, g , of the  
voltage error amplifier in each phase. Compensator capacitor C6  
m
Vo  
is then given by Equation 16.  
R2  
C3  
1
1
(EQ. 16)  
V
----------------  
------------------------  
C
=
,C =  
FB  
6
2
R ω  
2πR f  
-
V
6
cz  
6 esr  
COMP  
R3  
GM  
V
REF  
+
Example: V = 5V, V = 1.8V, I = 4A, fs = 1MHz,  
in  
o
o
R6  
C = 22µF/3mΩ, L = 1µH, GM = 160µs, R = 0.20V/A,  
o
FB  
t
C7  
5
V
= 0.6V, S = 440mV/µs, S = 6.4×10 V/s, f = 100kHz, then  
e n c  
C6  
compensator resistance R = 100kΩ.  
6
Put the compensator zero at 1.5kHz (~1.5x C R , and put the  
o o)  
compensator pole at ESR zero which is 390kHz. The  
compensator capacitors are:  
C = 220pF, C = 3pF (There is approximately 3pF parasitic  
6
7
FIGURE 42. TYPE II COMPENSATOR  
capacitance from V  
to GND; Therefore, C7 optional).  
COMP  
Figure 42 shows the type II compensator and its transfer function  
is expressed as Equation 14:  
Figure 43 shows the simulated voltage loop gain. It is shown that  
it has 90kHz loop bandwidth with 70° phase margin and 10dB  
gain margin.  
S
S
⎞ ⎛  
⎠ ⎝  
------------  
------------  
1 +  
1 +  
ˆ
v
ω
ω
(EQ. 14)  
GM  
comp  
cz1  
cz2  
---------------- ------------------- --------------------------------------------------------  
A (S)=  
=
v
ˆ
C
+ C  
2
S
60  
45  
30  
15  
0
v
FB  
1
---------  
S 1 +  
ω
cp  
where,  
C
+ C  
7
1
1
6
-------------  
-------------  
---------------------  
=
ω
=
,
ω
=
, ω  
cp  
cz1  
cz2  
R C  
R C  
R C C  
1 6 7  
6
6
2
3
Compensator design goal:  
High DC gain  
1
4
1
10  
-15  
-30  
-- ------  
to  
f
Loop bandwidth f :  
c
s
Gain margin: >10dB  
Phase margin: 40°  
100  
1k  
10k  
f (fi)  
100k  
1M  
The compensator design procedure is as follows:  
1
-------------  
= (1to3)  
ω
180  
cz1  
Put compensator zero  
R C  
o
o
Put one compensator pole at zero frequency to achieve high DC  
gain, and put another compensator pole at either ESR zero  
frequency or half switching frequency, whichever is lower. An  
optional zero can boost the phase margin. ωCZ2 is a zero due to  
R and C .  
150  
120  
90  
60  
30  
0
2
3
1
-------------  
ω
= (5to8)  
cz2  
Put compensator zero  
R C  
o
o
The loop gain T (S) at cross over frequency of f has unity gain.  
v
c
Therefore, the compensator resistance R is determined by  
1
Equation 15.  
2πf V C R  
(EQ. 15)  
100  
1k  
10k  
f (fi)  
100k  
1M  
c
o o t  
-------------------------------  
=
R
6
GM V  
FB  
FIGURE 43. SIMULATED LOOP GAIN  
FN7812.0  
December 22, 2011  
17  
ISL8023, ISL8024  
should be placed to VIN pin as close as possible. And the ground  
PCB Layout Recommendation  
of input and output capacitors should be connected as close as  
possible. The heat of the IC is mainly dissipated through the  
thermal pad. Maximizing the copper area connected to the  
thermal pad is preferable. In addition, a solid ground plane is  
helpful for better EMI performance. It is recommended to add at  
least 5 vias ground connection within the pad for the best  
thermal relief.  
The PCB layout is a very important converter design step to make  
sure the designed converter works well. For ISL8023, ISL8024,  
the power loop is composed of the output inductor Ls, the output  
capacitor COUT, the PHASE’s pins, and the PGND pin. It is  
necessary to make the power loop as small as possible and the  
connecting traces among them should be direct, short and wide.  
The switching node of the converter, the PHASE pins, and the  
traces connected to the node are very noisy, so keep the voltage  
feedback trace away from these noisy traces. The input capacitor  
Revision History  
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make  
sure you have the latest revision.  
DATE  
REVISION  
FN7812.0  
CHANGE  
12/22/2011  
Initial Release.  
Products  
Intersil Corporation is a leader in the design and manufacture of high-performance analog semiconductors. The Company's products  
address some of the industry's fastest growing markets, such as, flat panel displays, cell phones, handheld products, and notebooks.  
Intersil's product families address power management and analog signal processing functions. Go to www.intersil.com/products for a  
complete list of Intersil product families.  
For a complete listing of Applications, Related Documentation and Related Parts, please see the respective device information page on  
intersil.com: ISL8023, ISL8024  
To report errors or suggestions for this datasheet, please go to: www.intersil.com/askourstaff  
FITs are available from our website at: http://rel.intersil.com/reports/search.php  
For additional products, see www.intersil.com/product_tree  
Intersil products are manufactured, assembled and tested utilizing ISO9000 quality systems as noted  
in the quality certifications found at www.intersil.com/design/quality  
Intersil products are sold by description only. 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 data sheets are current before placing orders. Information furnished by Intersil is believed to be  
accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third  
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.  
For information regarding Intersil Corporation and its products, see www.intersil.com  
FN7812.0  
December 22, 2011  
18  
ISL8023, ISL8024  
Package Outline Drawing  
L16.3x3D  
16 LEAD THIN QUAD FLAT NO-LEAD PLASTIC PACKAGE  
Rev 0, 3/10  
4X 1.50  
3.00  
6
A
12X 0.50  
PIN #1  
INDEX AREA  
B
13  
16  
6
PIN 1  
INDEX AREA  
12  
1
1.60 SQ  
4
9
(4X)  
0.15  
0.10 M C A B  
16X 0.23±0.05  
8
5
16X 0.40±0.10  
TOP VIEW  
4
BOTTOM VIEW  
SEE DETAIL “X”  
0.10 C  
C
0.75 ±0.05  
0.08 C  
SIDE VIEW  
(12X 0.50)  
(2.80 TYP) ( 1.60)  
(16X 0.23)  
5
0 . 2 REF  
C
(16X 0.60)  
0 . 02 NOM.  
0 . 05 MAX.  
TYPICAL RECOMMENDED LAND PATTERN  
DETAIL "X"  
NOTES:  
1. Dimensions are in millimeters.  
Dimensions in ( ) for Reference Only.  
2. Dimensioning and tolerancing conform to ASME Y14.5m-1994.  
3.  
Unless otherwise specified, tolerance : Decimal ± 0.05  
4. Dimension applies to the metallized terminal and is measured  
between 0.15mm and 0.25mm from the terminal tip.  
Tiebar shown (if present) is a non-functional feature.  
5.  
6.  
The configuration of the pin #1 identifier is optional, but must be  
located within the zone indicated. The pin #1 identifier may be  
either a mold or mark feature.  
JEDEC reference drawing: MO-220 WEED.  
7.  
FN7812.0  
December 22, 2011  
19  

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