ISL85012FRZ-T7A [RENESAS]

12A, 3.8V to 18V Input, Synchronous Buck Regulator;
ISL85012FRZ-T7A
型号: ISL85012FRZ-T7A
厂家: RENESAS TECHNOLOGY CORP    RENESAS TECHNOLOGY CORP
描述:

12A, 3.8V to 18V Input, Synchronous Buck Regulator

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中文:  中文翻译
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DATASHEET  
ISL85012  
FN8677  
Rev.2.00  
Mar 17, 2017  
12A, 3.8V to 18V Input, Synchronous Buck Regulator  
The ISL85012 is a highly efficient, monolithic, synchronous  
buck regulator that can deliver 12A of continuous output  
current from a 3.8V to 18V input supply. The device uses  
current mode control architecture with a fast transient  
response and excellent loop stability.  
Features  
• Power input voltage range variable 3.8V to 18V  
• PWM output voltage adjustable from 0.6V  
• Up to 12A output load  
The ISL85012 integrates very low ON-resistance high-side and  
low-side FETs to maximize efficiency and minimize external  
component count. The minimum BOM and easy layout  
footprint are extremely friendly to space constraint systems.  
• Prebias start-up, fixed 3ms soft-start  
• Selectable f  
of 300kHz, 600kHz, and external  
SW  
synchronization up to 1MHz  
• Peak current mode control  
- DCM/CCM  
The operation frequency of this device can be set using the  
FREQ pin: 600kHz (FREQ = float) and 300kHz (FREQ = GND).  
The device can also be synchronized to an external clock up to  
1MHz.  
- Thermally compensated current limit  
- Internal/external compensation  
Both high-side and low-side MOSFET current limit along with  
reverse current limit, fully protects the regulator in an  
overcurrent event. Selectable OCP schemes can fit various  
applications. Other protections, such as input/output  
overvoltage and over-temperature, are also integrated into the  
device which give required system level safety in the event of  
fault conditions.  
• Open-drain, PG window comparator  
• Output overvoltage and thermal protection  
• Input overvoltage protection  
• Integrated boot diode with undervoltage detection  
• Selectable OCP schemes  
- Hiccup OCP  
The ISL85012 is offered in a space saving 15 Ld 3.5mmx3.5mm  
Pb-free TQFN package with great thermal performance and  
0.8mm maximum height.  
- Latch-off  
• Compact size 3.5mmx3.5mm  
Applications  
Related Literature  
• For a full list of related documents please visit our web page  
- ISL85012 product page  
• Servers and cloud infrastructure POLs  
• IPCs, factory automation, PLCs  
• Telecom and networking systems  
• Storage systems  
• Test measurement  
R1  
200k  
R2  
100k  
C5  
C1  
R3  
200  
1µF  
4.7pF  
15  
14  
13  
12  
11  
10  
FB  
VIN  
EN  
DNC DNC COMP  
VIN  
L1  
0.68µH  
PVIN  
9
8
3x22µF  
VOUT  
4.5-18V  
GND  
PHASE  
Cin  
COUT  
3x100µF  
CERAMIC  
1.8V/12A  
GND  
GND  
7
C4  
100nF  
SYNC MODE FREQ PG  
VDD BOOT  
1
2
3
4
5
6
C3  
2.2µF  
FIGURE 1. TYPICAL APPLICATION SCHEMATIC FOR INTERNAL COMPENSATION  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 1 of 19  
ISL85012  
Typical Application Schematic  
330pF  
C2  
R1  
20k  
  
80.6k  
R3  
C5  
1µF  
C1  
47pF  
15  
14  
13  
12  
DNC COMP  
11  
10  
R2  
10k  
FB  
VIN  
EN  
DNC  
VIN  
L1  
PVIN  
9
0.68µH  
VOUT  
4.5-18V  
GND  
PHASE  
8
3x22µF  
Cin  
3x100µF  
CERAMIC  
COUT  
1.8V/12A  
GND  
GND  
7
C4  
100nF  
SYNC MODE FREQ  
PG  
4
VDD BOOT  
1
2
3
5
6
C3  
2.2µF  
FIGURE 2. TYPICAL APPLICATION SCHEMATIC FOR EXTERNAL COMPENSATION  
TABLE 1. DESIGN TABLE FOR DIFFERENT OUTPUT VOLTAGE  
V
(V)  
0.9  
1
1.2  
4.5 to 18  
300  
1.5  
4.5 to 18  
600  
1.8  
4.5 to 18  
600  
2.5  
4.5 to 18  
600  
3.3  
5
6 to 18  
600  
OUT  
(V)  
V
4.5 to 18  
300  
4.5 to 18  
300  
4.5 to 18  
600  
IN  
FREQ (kHz)  
Compensation  
Internal  
3x22  
Internal  
3x22  
Internal  
3x22  
Internal  
3x22  
4x100  
0.68  
Internal  
3x22  
3x100  
0.68  
Internal  
3x22  
4x47  
1
Internal  
3x22  
4x47  
1
Internal  
3x22  
4x47  
1.5  
C
(µF)  
(µF)  
in  
C
2x560 + 4x100 2x330 + 3x100 2x330 + 3x100  
out  
L
(µH)  
(kΩ)  
(kΩ)  
(pF)  
0.68  
100  
200  
DNP  
0.68  
100  
150  
DNP  
1
1
R
R
147  
147  
DNP  
150  
200  
301  
365  
80.6  
3.3  
365  
1
2
100  
100  
95.3  
4.7  
49.9  
3.3  
C
10  
4.7  
1
NOTES:  
1. The design table is referencing the schematic shown in Figure 1.  
2. Ceramic capacitors are selected for 22µF and 100µF in the table.  
3. 560µF (14mΩ) and 330µF (10mΩ) are selected low ESR conductive polymer aluminum solid capacitors.  
4. Inductor 7443340068 (0.68µH), 7443340100 (1µH) and 7443340150 (1.5µH) from Wurth Electronics are selected for the above applications.  
5. Recommend to keep the inductor peak-to-peak current less than 5A.  
TABLE 2. KEY DIFFERENCES BETWEEN FAMILY OF PARTS  
INTERNAL/EXTERNAL  
COMPENSATION  
EXTERNAL FREQUENCY  
SYNC  
PROGRAMMABLE  
SOFT-START  
SWITCHING  
FREQUENCY (kHz)  
CURRENT  
RATING (A)  
PART NUMBER  
ISL85003  
Yes  
Yes  
Yes  
Yes  
Yes  
Yes  
No  
No  
Yes  
No  
500  
3
3
ISL85003A  
ISL85005  
500  
Yes  
No  
500  
500  
5
ISL85005A  
ISL85012  
Yes  
No  
5
Yes  
300 or 600 selectable  
12  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 2 of 19  
ISL85012  
Ordering Information  
PART NUMBER  
(Notes 6, 7, 8)  
TEMP. RANGE  
(°C)  
TAPE AND REEL  
(UNITS)  
PACKAGE  
(RoHS COMPLIANT)  
PKG.  
DWG. #  
PART MARKING  
5012  
ISL85012FRZ-T  
-40 to +125  
-40 to +125  
6k  
15 Ld 3.5mmx3.5mm TQFN  
15 Ld 3.5mmx3.5mm TQFN  
L15.3.5x3.5  
L15.3.5x3.5  
ISL85012FRZ-T7A  
ISL85012EVAL1Z  
NOTES:  
5012  
250  
Evaluation Board  
6. Refer to TB347 for details on reel specifications.  
7. 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.  
8. For Moisture Sensitivity Level (MSL), see product information page for ISL85012. For more information on MSL, see tech brief TB363.  
Functional Block Diagram  
PG  
NC  
FREQ  
SYNC  
EN  
VDD  
DELAY  
POR  
LDO  
VIN  
POWER-ON RESET MONITOR  
OSCILLATOR  
THERMAL  
SHUT  
OVP  
MODE  
DOWN  
PVIN  
UVP  
CSA  
FAULT  
MONITOR  
CIRCUITS  
20V  
HIGH SIDE  
OCP  
BOOT  
SCHEME  
SETTING  
BOOT  
UVP  
NC  
EA  
GATE DRIVER  
CONTROL LOGIC  
INTERNAL SS  
PHASE  
0.6V  
REF  
VDD  
FB  
SLOPE  
COMP  
800/1200k  
FREQ  
CSA  
30pF  
ZERO CROSS  
DETECTOR  
DCM  
COMP  
NEGATIVE  
GND  
CURRENT LIMIT  
AND FORWARD  
CURRENT LIMIT  
FIGURE 3. FUNCTIONAL BLOCK DIAGRAM  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 3 of 19  
ISL85012  
Pin Configuration  
ISL85012  
(15 LD 3.5mmx3.5mm TQFN)  
TOP VIEW  
15  
14  
13  
12  
11  
10  
VIN  
EN  
DNC DNC COMP FB  
PVIN  
9
PHASE  
8
GND  
7
SYNC MODE FREQ PG  
VDD BOOT  
1
2
3
4
5
6
Pin Descriptions  
PIN  
PIN#  
1
NAME  
DESCRIPTION  
SYNC Synchronization and mode selection pin. Connect to VDD or float for PWM mode. Connect to GND for DCM mode in the light-load  
condition. Connect to an external clock signal for synchronization with the rising edge trigger.  
2
3
4
MODE OCP scheme select pin. Short it to GND for latch-off mode. Float it for hiccup mode.  
FREQ Default frequency selection pin. Short it to GND for 300kHz. Float it for 600kHz.  
PG  
Power-good, open-drain output. It requires a pull-up resistor (10kΩ to 100kΩ) between PG and VDD or a voltage not exceeding  
5.5V. PG pulls high when FB is in the range of ~90% to ~116% of its intended value.  
5
6
VDD  
Low dropout linear regulator decoupling pin. The VDD is the internally generated 5V supply voltage and is derived from VIN. The  
VDD is used to power all the internal core analog control blocks and drivers. Connect a 2.2µF capacitor from VDD to the board  
ground plane. If the V is between 3V to 5.5V, then connect VDD directly to VIN to improve efficiency.  
IN  
BOOT BOOT is the floating bootstrap supply pin for the high-side power MOSFET gate driver. A bootstrap capacitor, usually 0.1µF, is  
required from BOOT to PHASE.  
7
8
GND  
Reference of the power circuit. For thermal relief, this pin should be connected to the ground plane by vias.  
PHASE Switch node connection to the internal power MOSFETs (source of upper FET and drain of lower FET) and the external output  
inductor.  
9
PVIN Input supply for the PWM regulator power stage. A decoupling capacitor, typically ceramic, is required to be connected between  
this pin and GND.  
10  
11  
FB  
Inverting input to the voltage loop error amplifier. The output voltage is set by an external resistor divider connected to FB.  
COMP Output of the error amplifier. Compensation network between COMP and FB to configure external compensation. Place a 200Ω  
resistor between COMP and GND for internal compensation, which is used to meet most applications.  
12, 13  
14  
DNC  
EN  
Do Not Connect to pin. Float the pins in the design.  
Enable input. The regulator is held off when this pin is pulled to ground. The device is enabled when the voltage on this pin rises  
to about 0.6V.  
15  
VIN  
Input supply for the control circuit and the source for the internal linear regulator that provides bias for the IC.  
A decoupling capacitor, typically 1µF ceramic, is required connected between VIN and GND.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 4 of 19  
ISL85012  
Absolute Maximum Ratings  
Thermal Information  
VIN, EN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +24V  
PVIN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +24V  
PHASE to GND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.7V to +24V (DC)  
PHASE to GND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -2V to +24V (40ns)  
BOOT to PHASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +7V  
VDD, COMP, SYNC, PG, FB, MODE, FREQ, SS, IOCP to GND . . . -0.3V to +7V  
ESD Rating  
Human Body Model (Tested per JS-001-2014). . . . . . . . . . . . . . . . .2.5kV  
Charged Device Model (Tested per JS-002-2014) . . . . . . . . . . . . . . . 1kV  
Latch-Up (Tested per JESD78E; Class 2, Level A, +125°C). . . . . . .100mA  
Thermal Resistance  
TQFN Package (Notes 9, 10). . . . . . . . . . . .  
Maximum Storage Temperature Range . . . . . . . . . . . . . .-65°C to +150°C  
Junction Temperature Range . . . . . . . . . . . . . . . . . . . . . . .-55°C to +150°C  
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see TB49  
(°C/W)  
33  
(°C/W)  
1.2  
JA  
JC  
Recommended Operating Conditions  
VIN Supply Voltage Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5V to 18V  
PVIN Supply Voltage Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8V to 18V  
Load Current Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0A to 12A  
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:  
9. is measured in free air with the component mounted on a high-effective thermal conductivity test board with “direct attach” features, except with  
JA  
3 vias under the GND EPAD strip contacting the GND plane, and two vias under the VIN EPAD strip contacting the VIN plane. See Tech Brief TB379.  
10. For , the “case temp” location is 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 +125°C, V = 4.5V to 18V, unless otherwise noted. Typical values are at  
J
IN  
T
= +25°C. Boldface limits apply across the operating temperature range, -40°C to +125°C.  
A
MIN  
MAX  
PARAMETER  
SYMBOL  
TEST CONDITIONS  
(Note 11) TYP (Note 11) UNIT  
SUPPLY VOLTAGE  
PVIN Voltage Range  
3.8  
4.5  
18  
18  
5
V
V
PVIN  
VIN  
V
V
V
Voltage Range  
IN  
IN  
IN  
Quiescent Supply Current  
Shutdown Supply Current  
I
EN = 2V, FB = 0.64V  
EN = GND  
3
8
mA  
µA  
Q
I
13  
SD  
POWER-ON RESET  
PVIN POR Threshold  
Rising edge  
Falling edge  
Rising edge  
Falling edge  
Rising edge  
Hysteresis  
2.9  
4.49  
0.7  
V
V
1.9  
V
POR Threshold  
V
IN  
3.4  
0.5  
V
EN POR Threshold  
0.6  
V
100  
mV  
V
V
POR Threshold  
Rising edge  
Falling edge  
3.6  
DD  
2.4  
4.3  
V
INTERNAL VDD LDO  
V
V
Output Voltage Regulation Range  
Output Current Limit  
V
= 6V to 18V, I  
VDD  
= 0mA to 30mA  
5.0  
80  
5.5  
V
mA  
V
DD  
DD  
IN  
IN  
LDO Dropout Voltage  
OSCILLATOR  
V
= 5V, I  
VDD  
= 30mA  
0.65  
Nominal Switching Frequency  
Nominal Switching Frequency  
Minimum On-Time  
f
f
FREQ = float  
FREQ = GND  
540  
250  
600  
280  
90  
660  
310  
150  
170  
1000  
0.5  
kHz  
kHz  
ns  
SW1  
SW2  
t
I
= 0mA  
ON  
OUT  
Minimum Off-Time  
t
140  
ns  
OFF  
Synchronization Range  
SYNC Logic Input Low  
SYNC Logic Input High  
100  
1.2  
kHz  
V
V
FN8677 Rev.2.00  
Mar 17, 2017  
Page 5 of 19  
ISL85012  
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 +125°C, V = 4.5V to 18V, unless otherwise noted. Typical values are at  
J
IN  
T
= +25°C. Boldface limits apply across the operating temperature range, -40°C to +125°C. (Continued)  
A
MIN  
MAX  
PARAMETER  
SYMBOL  
TEST CONDITIONS  
(Note 11) TYP (Note 11) UNIT  
ERROR AMPLIFIER  
FB Regulation Voltage  
FB Leakage Current  
Open Loop Bandwidth  
Gain  
V
0.588  
0.600  
0.612  
10  
V
nA  
FB  
V
= 0.6V  
FB  
BW  
5.5  
70  
MHz  
dB  
Output Drive  
High-side clamp = 1.5V, low-side clamp = 0.4V  
Tested at 600kHz  
±100  
0.055  
470  
µA  
Current-Sense Gain  
Slope Compensation  
SOFT-START  
RT  
Se  
0.050  
1.9  
0.063  
4.7  
Ω
mV/µs  
Default Soft-Start Time  
PG  
3
ms  
Output Low Voltage  
PG Pin Leakage Current  
PG Lower Threshold  
PG Upper Threshold  
PG Thresholds Hysteresis  
Delay Time  
I
= 5mA  
0.3  
0.01  
87  
V
µA  
%
PG  
Percentage of output regulation  
Percentage of output regulation  
SYNC is short-to-GND  
Rising edge  
81  
92  
110  
116  
3
121  
%
%
1.5  
23  
ms  
µs  
Falling edge  
FAULT PROTECTION  
V
/PVIN Overvoltage Lockout  
IN  
Rising edge  
19  
18  
20.5  
19.5  
1
22  
21  
V
V
Falling edge  
Hysteresis  
V
A
Positive Overcurrent Protection Threshold  
I
High-side OCP  
15.5  
-10.8  
110  
18  
19.5  
-5.5  
121  
POCP  
Low-side OCP  
21  
A
Negative Overcurrent Protection Threshold  
Hiccup Blanking Time  
I
Current forced into PHASE node, high-side MOSFET is off  
-7.5  
150  
116  
160  
10  
NOCP  
ms  
%
FB Overvoltage Threshold  
Thermal Shutdown Temperature  
T
Rising threshold  
Hysteresis  
°C  
°C  
SD  
T
HYS  
POWER MOSFET  
High-Side  
R
IPHASE = 900mA  
IPHASE = 900mA  
EN = GND  
15  
7
mΩ  
mΩ  
kΩ  
HDS  
Low-Side  
R
LDS  
PHASE Pull-Down Resistor  
NOTE:  
22.5  
11. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 6 of 19  
ISL85012  
Typical Performance Curves Circuit of Figure 2. Design table on page 2 shows the components value for different  
output voltages. Plots are captured from ISL85012EVAL1Z boards. V = 12V, V  
= 1.8V, FREQ = 600kHz, CCM, T = -40°C to +125°C unless otherwise  
IN  
OUT J  
noted. Typical values are at T = +25°C.  
A
100  
90  
80  
70  
60  
50  
40  
100  
90  
80  
70  
60  
50  
40  
30  
20  
5V  
3.3V  
1.5V  
1V  
1.2V  
30  
20  
1.8V  
0.9V  
0
2
4
6
8
10  
12  
0
2
4
6
8
10  
12  
12  
12  
OUTPUT CURRENT (A)  
OUTPUT CURRENT (A)  
FIGURE 4. EFFICIENCY vs LOAD (V = 12V, CCM, 600kHz)  
IN  
FIGURE 5. EFFICIENCY vs LOAD (V = 12V, CCM, 300kHz)  
IN  
100  
100  
90  
80  
70  
60  
50  
40  
30  
20  
90  
80  
70  
60  
50  
40  
30  
20  
3.3V  
1.5V  
1.8V  
1V  
0.9V  
1.2V  
0
2
4
6
8
10  
12  
0
2
4
6
8
10  
OUTPUT CURRENT (A)  
OUTPUT CURRENT (A)  
FIGURE 6. EFFICIENCY vs LOAD (V = 5V, CCM, 600kHz)  
IN  
FIGURE 7. EFFICIENCY vs LOAD (V = 5V, CCM, 300kHz)  
IN  
1.010  
1.009  
1.008  
1.007  
1.006  
1.005  
1.004  
1.003  
1.002  
1.816  
1.814  
1.812  
1.810  
1.808  
1.806  
1.804  
1.802  
1.800  
1.001  
1.798  
1.8V  
1.796  
1V  
1.000  
0
2
4
6
8
10  
12  
0
2
4
6
8
10  
OUTPUT CURRENT (A)  
OUTPUT CURRENT (A)  
FIGURE 8. V  
REGULATION vs LOAD (V = 12V, CCM, 600kHz)  
IN  
FIGURE 9. V  
REGULATION vs LOAD (V = 12V, CCM, 300kHz)  
OUT IN  
OUT  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 7 of 19  
ISL85012  
Typical Performance Curves Circuit of Figure 2. Design table on page 2 shows the components value for different  
output voltages. Plots are captured from ISL85012EVAL1Z boards. V = 12V, V  
= 1.8V, FREQ = 600kHz, CCM, T = -40°C to +125°C unless otherwise  
IN  
OUT J  
noted. Typical values are at T = +25°C. (Continued)  
A
C2: PHASE, 10V/DIV  
C2: PHASE, 10V/DIV  
C1: V  
, 1V/DIV  
OUT  
C1: V  
, 1V/DIV  
OUT  
50ms/DIV  
50ms/DIV  
FIGURE 10. LATCH-OFF OCP (V = 12V, V  
IN  
= 1.8V, 600kHz, CCM)  
FIGURE 11. HICCUP OCP (V = 12V, V  
= 1.8V, 600kHz, CCM)  
OUT  
OUT  
IN  
C2: PHASE, 10V/DIV  
C2: PHASE, 10V/DIV  
C1: V  
, 20mV/DIV  
OUT  
C1: V  
, 20mV/DIV  
OUT  
1µs/DIV  
10ms/DIV  
FIGURE 12. OUTPUT VOLTAGE RIPPLE (V = 12V, V  
IN  
= 1.8V AT  
FIGURE 13. OUTPUT VOLTAGE RIPPLE (V = 12V, V  
= 1.8V AT 0A,  
OUT  
OUT  
IN  
12A, 600kHz, CCM)  
600kHz, DCM)  
C3: EN, 10V/DIV  
C3: EN, 10V/DIV  
C1: V  
, 1V/DIV  
C1: V  
, 1V/DIV  
OUT  
OUT  
C4: PGOOD, 2V/DIV  
C4: PGOOD, 2V/DIV  
2ms/DIV  
2ms/DIV  
FIGURE 14. START-UP BY EN (V = 12V, V  
IN  
= 1.8V AT 12A,  
FIGURE 15. START-UP BY EN (V = 12V, V  
= 1.8V AT 0A, 600kHz,  
OUT  
OUT  
IN  
600kHz, CCM)  
DCM)  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 8 of 19  
ISL85012  
Typical Performance Curves Circuit of Figure 2. Design table on page 2 shows the components value for different  
output voltages. Plots are captured from ISL85012EVAL1Z boards. V = 12V, V  
= 1.8V, FREQ = 600kHz, CCM, T = -40°C to +125°C unless otherwise  
IN  
OUT J  
noted. Typical values are at T = +25°C. (Continued)  
A
C3: EN, 10V/DIV  
C3: EN, 10V/DIV  
C1: V  
, 1V/DIV  
OUT  
C1: V  
, 1V/DIV  
OUT  
C4: PGOOD, 2V/DIV  
C4: PGOOD, 2V/DIV  
1ms/DIV  
50ms/DIV  
FIGURE 16. SHUTDOWN BY EN (V = 12V, V  
IN  
= 1.8V AT 12A,  
FIGURE 17. SHUTDOWN BY EN (V = 12V, V  
= 1.8V AT 0A,  
OUT  
OUT  
IN  
600kHz, CCM)  
600kHz, DCM)  
Typical Characteristics  
12  
10  
8
4.0  
3.8  
3.6  
3.4  
3.2  
3.0  
2.8  
2.6  
2.4  
2.2  
2.0  
6
4
2
0
-40 -25 -10  
5
20  
35  
50 65  
80  
95 110 125  
-40 -25 -10  
5
20 35 50  
65 80 95 110 125  
JUNCTION TEMPERATURE (°C)  
JUNCTION TEMPERATURE (°C)  
FIGURE 18. V SHUTDOWN CURRENT vs TEMPERATURE  
IN  
FIGURE 19. V QUIESCENT CURRENT vs TEMPERATURE  
IN  
0.606  
0.604  
0.602  
0.600  
0.598  
0.596  
0.594  
0.65  
0.63  
0.61  
0.59  
0.57  
0.55  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
JUNCTION TEMPERATURE (°C)  
JUNCTION TEMPERATURE (°C)  
FIGURE 20. FEEDBACK VOLTAGE vs TEMPERATURE  
FIGURE 21. ENABLE THRESHOLD vs TEMPERATURE  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 9 of 19  
ISL85012  
Typical Characteristics (Continued)  
4.130  
4.125  
4.120  
4.115  
4.110  
4.105  
4.100  
3.72  
3.71  
3.70  
3.69  
3.68  
3.67  
3.66  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
JUNCTION TEMPERATURE (°C)  
JUNCTION TEMPERATURE (°C)  
FIGURE 22. V POR (RISING) vs TEMPERATURE  
IN  
FIGURE 23. V POR (FALLING) vs TEMPERATURE  
IN  
700  
680  
660  
640  
620  
600  
580  
560  
540  
520  
500  
400  
380  
360  
340  
320  
300  
280  
260  
240  
220  
200  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
JUNCTION TEMPERATURE (°C)  
JUNCTION TEMPERATURE (°C)  
FIGURE 24. FREQUENCY (600kHz DEFAULT) vs TEMPERATURE  
FIGURE 25. FREQUENCY (300kHz DEFAULT) vs TEMPERATURE  
1.40  
1.35  
1.30  
1.25  
1.20  
1.15  
1.10  
25  
20  
15  
10  
5
0
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
-40 -25 -10  
5
20  
35  
50  
65  
80  
95 110 125  
JUNCTION TEMPERATURE (°C)  
JUNCTION TEMPERATURE (°C)  
FIGURE 26. PG DELAY vs TEMPERATURE  
FIGURE 27. HIGH-SIDE r  
vs TEMPERATURE  
DS(ON)  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 10 of 19  
ISL85012  
Typical Characteristics (Continued)  
10  
9
8
7
6
5
4
3
2
1
0
-40 -25 -10  
5
20  
35  
50 65  
80  
95 110 125  
JUNCTION TEMPERATURE (°C)  
FIGURE 28. LOW-SIDE r  
vs TEMPERATURE  
DS(ON)  
Enable and Soft-Start  
Detailed Description  
Chip operation begins after V PVIN, and V exceed their rising  
IN, DD  
The ISL85012 combines a synchronous buck controller with a  
pair of integrated switching MOSFETs. The buck controller drives  
the internal high-side and low-side N-channel MOSFETs to deliver  
load currents up to 12A. The buck regulator can operate from an  
unregulated DC source, such as a battery, with a voltage ranging  
from +3.8V to +18V. An internal 5V LDO voltage regulator is used  
to bias the controller. The converter output voltage is  
programmed using an external resistor divider and will generate  
regulated voltages down to 0.6V. These features make the  
regulator suited for a wide range of applications.  
POR trip points. If EN is held low externally, nothing happens until  
this pin is released. Once the voltage on the EN pin is above 0.6V,  
the LDO powers up and soft-start control begins. The ISL85012  
operates at Discontinuous Conduction Mode (DCM) during  
soft-start. The soft-start time is 3ms. EN can be directly driven by  
VIN or an external power supply. It is recommended to add an RC  
filter at the EN pin if the signal which drives the EN is noisy.  
The part is designed supporting start-up into a prebiased load  
(the prebiased voltage requires to be less than the setting output  
voltage). Both high-side and low-side switches are disabled until  
the internal SS voltage exceeds the FB voltage during start-up.  
The controller uses a current mode loop, which simplifies the  
loop compensation and permits fixed frequency operation over a  
wide range of input and output voltages. The internal feedback  
loop compensation option allows for simple circuit design.  
600kHz (FREQ = float) and 300kHz (FREQ = GND) can be  
selected as the default switching frequency. The regulator can be  
synchronized from 100kHz to 1MHz by SYNC pin as well.  
PWM Control Scheme  
The ISL85012 employs the current-mode Pulse-Width  
Modulation (PWM) control scheme for fast transient response.  
The current loop consists of the oscillator, the PWM comparator,  
current sensing circuit, and the slope compensation circuit. The  
gain of the current sensing circuit is typically 55mV/A and the  
The buck regulator is equipped with a lossless current limit  
scheme. The current in the output stage is derived from  
temperature compensated measurements of the drain-to-source  
voltage of the internal power MOSFETs.  
slope compensation is 780mV/t (t = period). The control  
SS SS  
reference for the current loop comes from the Error Amplifier’s  
(EA) output, which compares the feedback signal at FB pin to the  
integrated 0.6V reference.  
Operation Initialization  
The power-on reset circuitry and enable inputs prevent false  
start-up of the PWM regulator output. Once all the input criteria  
are met (see Figure 29), the controller soft-starts the output  
voltage to the programmed level.  
Setting as internal compensation (COMP short to GND through a  
200Ω resistor), the voltage loop is internally compensated with a  
30pF and 800kΩ RC network either the switching regulator  
works at default 600kHz (FREQ = float) or it is synchronized  
externally by SYNC pin. A 30pF and 1200kΩ RC network is  
implemented for internal compensation when It works at default  
300kHz (FREQ = GND).  
EN  
0.6V  
POR  
VIN  
4.4V  
VDD  
3.4V  
PVIN  
3.8V  
FIGURE 29. POR CIRCUIT  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 11 of 19  
ISL85012  
The PWM operation is initialized by the clock from the oscillator.  
The high-side 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  
The output voltage programming resistor, R , will depend on the  
2
value chosen for the feedback resistor, R , and the desired  
1
output voltage, V  
; see Equation 2. The R value will  
OUT  
1
determine the gain of the feedback loop. See “Loop  
(780mV/t ) reaches the control reference of the current loop  
Compensation Design” on page 15 for more details. The value for  
the feedback resistor is typically between 1kΩ and 370kΩ.  
SS  
(COMP), the PWM comparator sends a signal to the PWM logic to  
turn off the upper MOSFET and turn on the lower MOSFET. The  
lower MOSFET stays on until the end of the PWM cycle. Figure 30  
shows the typical operating waveforms during Continuous  
Conduction Mode (CCM) operation. The dotted lines illustrate  
the sum of the compensation ramp and the current-sense  
amplifier’s output.  
R
0.6V  
1
----------------------------------  
R
=
(EQ. 2)  
2
V
0.6V  
OUT  
If the desired output voltage is 0.6V, then R is left unpopulated.  
2
R is still required to set the low frequency pole of the modulator  
1
compensation.  
V
V
OUT  
EAMP  
R
R
1
V
CSA  
-
+
DUTY  
CYCLE  
EA  
2
0.6V  
REFERENCE  
I
L
V
OUT  
FIGURE 31. EXTERNAL RESISTOR DIVIDER  
Protection Features  
FIGURE 30. PWM OPERATION WAVEFORMS  
The regulator limits current in all on-chip power devices.  
Overcurrent limits are applied to the two output switching  
MOSFETs as well as to the LDO linear regulator that feeds V  
The output overvoltage protection circuitry on the switching  
regulator provides a second layer of protection.  
Light-Load Operation  
The ISL85012 monitor both the current in the low-side MOSFET  
and the voltage of the FB node for regulation. Pulling the SYNC  
pin low allows the regulator to enter discontinuous operation  
when lightly loaded by operating the low-side MOSFET in Diode  
Emulation Mode (DEM). In this mode, reverse current is not  
allowed in the inductor and the output falls naturally to the  
regulation voltage before the high-side MOSFET is switched for  
the next cycle. In CCM mode, the boundary is set by Equation 1:  
.
DD  
High-Side MOSFET Overcurrent Protection  
Current flowing through the internal high-side switching MOSFET  
is monitored during on-time. The current, which is temperature  
compensated, will compare to a default 18A overcurrent limit.  
The ISL85012 offers two OCP schemes to implement the on-time  
overcurrent protection, which can be configured by the MODE pin  
(see Table 4).  
V
1 D  
OUT  
(EQ. 1)  
----------------------------------  
=
I
OUT  
2Lf  
SW  
where D = duty cycle, f  
= switching frequency, L = inductor  
SW  
= output loading current, and V  
TABLE 4. OCP SCHEME SETTING  
MODE  
value, I  
= output voltage.  
OUT  
OUT  
Table 3 shows the operating modes determined by the SYNC pin.  
Float  
GND  
TABLE 3. OPERATION MODE SETTING  
SYNC  
Enter hiccup mode after eight  
consecutive cycle-by-cycle limit.  
Blanking time is 150ms  
Enter latch-off mode after  
eight consecutive cycle-by-cycle  
limit  
Float  
GND  
DEM  
Force CCM  
If the measured current exceeds the overcurrent limit, the high-side  
MOSFET is immediately turned off and will not turn on again until  
the next switching cycle. After eight consecutive cycles of overcurrent  
events detected, the converter will operate at the selected OCP  
scheme according to the MODE pin configuration. A cycle where an  
overcurrent condition is not detected will reset the counter.  
Synchronization  
The ISL85012 can be synchronized from 100kHz to 1MHz by an  
external signal applied to the SYNC pin. The rising edge on the SYNC  
triggers the rising edge of the PHASE pulse. Make sure the on-time  
of the SYNC pulse is longer than 100ns.  
The switching frequency will be folded back if the OCP is tripped  
and the on-time of the PWM is less than 250ns to lower down the  
average inductor current.  
Output Voltage Selection  
The regulator output voltages can be programmed using external  
resistor dividers that scale the voltage feedback relative to the  
internal reference voltage. The scaled voltage is fed back to the  
inverting input of the error amplifier; refer to Figure 31.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 12 of 19  
ISL85012  
Low-Side MOSFET Overcurrent Protection  
BOOT Undervoltage Detection  
Low-side current limit consists of forward current limit (from GND  
to PHASE) and reverse current limit (from PHASE to GND).  
The internal driver of the high-side FET is equipped with a BOOT  
Undervoltage (UV) detection circuit. In the event the voltage  
difference between BOOT and PHASE falls below 2.8V, the UV  
detection circuit allows the low-side MOSFET on for 250ns, to  
recharge the bootstrap capacitor.  
Current through the low-side switching MOSFET is sampled  
during off time. The low-side OCP comparator is flagged if the  
low-side MOSFET current exceeds 21A (forward). It resets the flag  
when the current falls below 15A. The PWM will skip cycles when  
the flag is set, allowing the inductor current to decay to a safe  
level before resuming switching (see Figure 32).  
While the ISL85012 includes an internal bootstrap diode,  
efficiency can be improved by using an external supply voltage  
and bootstrap Schottky diode. The external diode is then sourced  
from a fixed external 5V supply or from the output of the  
switching regulator if this is at 5V. The bootstrap diode can be a  
low cost type, such as the BAT54 (see Figure 33).  
Similar to the forward overcurrent, the reverse current protection  
is realized by monitoring the current across the low-side MOSFET.  
When the low-side MOSFET current reaches -7.5A, the  
synchronous rectifier is turned off. This limits the ability of the  
regulator to actively pull-down on the output.  
Power-Good  
ISL85012 has a Power-Good (PG) indicator which is an open drain  
of a MOSFET. It requires pull-up to VDD or other voltage source  
lower than 5.5V through a resistor (usually from 10k to 100kΩ).  
The PG asserted 1.5ms after the FB voltage reaches 90% of the  
reference voltage in soft-start. It pulls low if the FB voltage drops to  
87% of the reference voltage or exceeds 116% of the reference  
voltage during the normal operation. Disabling the part also pulls  
the PG low. The PG will reassert when the FB voltage drops back to  
113% (100%) of the reference voltage after tripping the  
21A  
20A  
18A  
I
L
15A  
overvoltage protection when SYNC is low (float/high).  
PWM  
PHASE  
CLOCK  
C
4
0.1µF  
BOOT  
FIGURE 32. LOW-SIDE FORWARD OCP  
ISL85012  
Output Overvoltage Protection  
BAT54  
5V  
The overvoltage protection triggers when the output voltage  
exceeds 116% of the set voltage. In this condition, high-side and  
low-side MOSFETs are off until the output drops to within the  
regulation band. Once the output is in regulation, the controller  
will restart under internal SS control.  
OR 5V SOURCE  
OUT  
FIGURE 33. EXTERNAL BOOTSTRAP DIODE  
Application Guidelines  
Input Overvoltage Protection  
The input overvoltage protection system prevents operation of  
the switching regulator whenever the input voltage is higher than  
20V. The high-side and low-side MOSFETs are off and the  
converter will restart under internal SS control when the input  
voltage returns to normal.  
Buck Regulator Output Capacitor Selection  
An output capacitor is required to filter the inductor current and  
supply the load transient current. The filtering requirements are a  
function of the switching frequency, the ripple current and the  
required output ripple. The load transient requirements are a  
function of the slew rate (di/dt) and the magnitude of the  
transient load current. These requirements are generally met  
with a mix of capacitor types and careful layout.  
Thermal Overload Protection  
Thermal overload protection limits the maximum die  
temperature, and thus the total power dissipation in the  
regulator. A sensor on the chip monitors the junction  
temperature. A signal is sent to the fault monitor circuits  
High frequency ceramic capacitors initially supply the transient  
and slow the current load rate seen by the bulk capacitors. The  
bulk filter capacitor values are generally determined by the  
Equivalent Series Resistance (ESR) and voltage rating  
whenever the junction temperature (T ) exceeds +160°C, which  
J
causes the switching regulator and LDO to shut down.  
requirements rather than actual capacitance requirements.  
The switching regulator turns on again and soft-starts after the  
IC’s junction temperature cools by 10°C. The switching regulator  
exhibits hiccup mode operation during continuous thermal  
overload conditions. For continuous operation, do not exceed the  
+125°C junction temperature rating.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 13 of 19  
ISL85012  
2
L
I  
out TRAN  
(EQ. 5)  
(EQ. 6)  
--------------------------------------------------------------  
=
V  
V  
SAG  
2C  
 V V  
OUT  
OUT  
IN  
DV  
HUMP  
2
L
I  
out TRAN  
-----------------------------------------  
=
HUMP  
V
2C  
V  
OUT  
OUT  
OUT  
DV  
ESR  
where I  
= Output Load Current Transient and C  
= Total  
OUT  
TRAN  
Output Capacitance.  
DV  
DV  
SAG  
In a typical converter design, the ESR of the output capacitor  
bank dominates the transient response. The ESR and the ESL are  
typically the major contributing factors in determining the output  
capacitance. The number of output capacitors can be  
ESL  
I
OUT  
determined by using Equation 7, which relates the ESR and ESL  
of the capacitors to the transient load step and the tolerable  
I
tran  
output voltage excursion during load transient (V ):  
o
ESL I  
TRAN  
----------------------------------  
+ ESR I  
TRAN  
dt  
(EQ. 7)  
-----------------------------------------------------------------------------  
Number of Capacitors =  
V  
o
If V  
SAG  
and/or V are found to be too large for the output  
HUMP  
FIGURE 34. TYPICAL TRANSIENT RESPONSE  
voltage limits, then the amount of capacitance may need to be  
increased. In this situation, a trade-off between output  
inductance and output capacitance may be necessary.  
High frequency decoupling capacitors should be placed as close  
to the power pins of the load as physically possible. Be careful  
not to add inductance in the circuit board wiring that could  
cancel the usefulness of these low inductance components.  
Consult with the manufacturer of the load on specific decoupling  
requirements.  
The ESL of the capacitors, which is an important parameter in  
the previous equations, is not usually listed in specification.  
Practically, it can be approximated using Equation 8 if an  
Impedance vs Frequency curve is given for a specific capacitor:  
The shape of the output voltage waveform during a load transient  
that represents the worst case loading conditions, will ultimately  
determine the number of output capacitors and their type. When  
this load transient is applied to the converter, most of the energy  
required by the load is initially delivered from the output  
capacitors. This is due to the finite amount of time required for  
the inductor current to slew up to the level of the output current  
required by the load. This phenomenon results in a temporary dip  
in the output voltage. At the very edge of the transient, the  
Equivalent Series Inductance (ESL) of each capacitor induces a  
spike that adds on top of the existing voltage drop due to the  
Equivalent Series Resistance (ESR).  
1
(EQ. 8)  
----------------------------------------  
ESL =  
2
C2    f  
res  
where f is the frequency where the lowest impedance is  
res  
achieved (resonant frequency).  
The ESL of the capacitors becomes a concern when designing  
circuits that supply power to loads with high rates of change in  
the current.  
Output Inductor Selection  
The output inductor is selected to meet the output voltage ripple  
requirements and minimize the converter’s response time to the  
load transient. The inductor value determines the converter’s  
ripple current and the ripple voltage is a function of the ripple  
current. The ripple voltage and current are approximated by  
Equations 9 and 10:  
After the initial spike, attributable to the ESR and ESL of the  
capacitors, the output voltage experiences sag. This sag is a  
direct consequence of the amount of capacitance on the output.  
During the removal of the same output load, the energy stored in  
the inductor is dumped into the output capacitors. This energy  
dumping creates a temporary hump in the output voltage. This  
hump, as with the sag, can be attributed to the total amount of  
capacitance on the output. Figure 34 shows a typical response to  
a load transient.  
V V  
V  
OUT  
IN  
OUT  
(EQ. 9)  
------------------------------------ ---------------  
I =  
V  
f
L  
V
IN  
SW  
(EQ. 10)  
= I ESR  
OUT  
The amplitudes of the different types of voltage excursions can  
be approximated using Equations 3, 4, 5 and 6.  
Increasing the value of inductance reduces the ripple current and  
voltage. However, the large inductance values reduce the  
converter’s response time to a load transient. It is recommended  
to set the ripple inductor current to approximately 30% of the  
maximum output current for optimized performance.  
Recommend the design of the inductor ripple current does not  
exceeds 5A in the applications of ISL85012.  
V  
= ESR I  
(EQ. 3)  
ESR  
TRAN  
I
TRAN  
dt  
(EQ. 4)  
----------------  
V  
= ESL   
ESL  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 14 of 19  
ISL85012  
One of the parameters limiting the converter’s response to a load  
transient is the time required to change the inductor current.  
Given a sufficiently fast control loop design, the ISL85012 will  
provide either 0% or 100% duty cycle in response to a load  
transient. The response time is the time required to slew the  
inductor current from an initial current value to the transient  
current level. During this interval, the difference between the  
inductor current and the transient current level must be supplied  
by the output capacitor. Minimizing the response time can  
minimize the output capacitance required.  
Loop Compensation Design  
When COMP is not connected to GND through a 200Ω resistor,  
the COMP pin is active for external loop compensation. The  
regulator uses constant frequency peak current mode control  
architecture to achieve a fast loop transient response. An  
accurate current sensing pilot device in parallel with the  
high-side switch 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 a 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 an inherent  
input voltage feed-forward function to achieve good line  
regulation. Figure 35 shows the small signal model of the  
synchronous buck regulator.  
The response time to a transient is different for the application of  
load and the removal of load. Equations 11 and 12 give the  
approximate response time interval for application and removal  
of a transient load:  
L x I  
TRAN  
- V  
(EQ. 11)  
t
=
RISE  
V
IN OUT  
VIN  
d
L
DCR  
R
IL  
Vo  
L x I  
1:D  
ILd  
TRAN  
VOUT  
VIN  
(EQ. 12)  
t
=
FALL  
c
Ro  
where I  
is the transient load current step, t  
is the  
is the  
TRAN  
response time to the application of load, and t  
RISE  
Rt  
FALL  
Co  
response time to the removal of load. The worst case response  
time can be either at the application or removal of load. Be sure  
to check both of these equations at the minimum and maximum  
output levels for the worst case response time.  
Ti(s)  
d
Fm  
Input Capacitor Selection  
He(s)  
Use a mix of input bypass capacitors to control the input voltage  
ripple. Use ceramic capacitors for high frequency decoupling and  
bulk capacitors to supply the current needed each time the  
switching MOSFET turns on. Place the ceramic capacitors  
physically close to the MOSFET VIN pins (switching MOSFET  
drain) and PGND.  
Tv(s)  
-Av(s)  
Vcomp  
FIGURE 35. SMALL SIGNAL MODEL OF SYNCHRONOUS BUCK  
REGULATOR  
The important parameters for the bulk input capacitance are the  
voltage rating and the RMS current rating. For reliable operation,  
select bulk capacitors with voltage and current ratings above the  
maximum input voltage and largest RMS current required by the  
circuit. Their voltage rating should be at least 1.25 times greater  
than the maximum input voltage, while a voltage rating of 1.5  
times is a conservative guideline. For most cases, the RMS  
current rating requirement for the input capacitor of a buck  
regulator is approximately 1/2 the DC load current.  
To simplify the analysis, sample and hold effect block He(s) and  
slope compensation are not taken into account. Assume V  
comp  
is equal to the current sense signal ILxRt and ignore the DCR of  
the inductor, the power train can be approximated by a voltage  
controlled current source supplying current to the output  
capacitor and load resistor (see Figure 36). The transfer function  
frequency response is presented in Figure 37.  
L
V
o
The maximum RMS current required by the regulator may be  
closely approximated through Equation 13:  
I
L
R
c
2
R
o
VOUT  
-------------  
VIN  
V
IN VOUT VOUT  
   
   
   
V
comp  
2
1
12  
------ ---------------------------- -------------  
IRMS  
=
I  
+
OUT  
1/R  
t
L f  
VIN  
MAX  
MAX  
SW  
(EQ. 13)  
C
o
For a through-hole design, several electrolytic capacitors may be  
needed, especially at temperatures less than -25°C. The  
electrolytic's ESR can increase ten times higher than at room  
temperature and cause input line oscillation. In this case, a more  
thermally stable capacitor such as X7R ceramic should be used.  
For surface mount designs, solid tantalum capacitors can be  
used, but caution must be exercised with regard to the capacitor  
surge current rating. Some capacitor series available from  
reputable manufacturers are surge current tested.  
FIGURE 36. POWER TRAIN SMALL SIGNAL MODEL  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 15 of 19  
ISL85012  
fp  
Gdc  
R3/R1  
fz2  
fz1  
fpc fc  
fc  
fz  
FIGURE 39. POWER TRAIN FREQUENCY RESPONSE  
Design example: V = 12V, V = 1.8V, I = 10A, f  
= 600kHz,  
R = 200kΩ, R = 100kΩ, C = 3x100µF/3mΩ 6.3V ceramic  
FIGURE 37. POWER TRAIN SMALL FREQUENCY RESPONSE  
IN SW  
O
O
1
2
o
The simplified transfer function is derived in Equation 14.  
(actually ~150µF), L = 0.68µH.  
S
------  
1 +  
Select f = 80kHz. The gain of the Gp(s)xAv(s) should has a unity  
c
ˆ
v
o
z
(EQ. 14)  
gain at crossover frequency. Thus, R can be derived as:  
----------------  
comp  
----------------  
GpS=  
= Gdc  
3
ˆ
S
v
------  
1 +  
(EQ. 17)  
p
R
= 2f C R R = 829k  
c o t 1  
3
where:  
Select 800kΩ for R . Place the zero f around the pole fp to  
achieve -20db/dec roll off.  
3
z1  
R
1
1
o
------  
-----------------  
------------------------------------  
Gdc =  
; = 2fz =  
; = 2fp =  
z
p
R
t
R xC  
R + R xC  
o c  
c
o
o
Ro + RcxC  
o
(EQ. 15)  
(EQ. 18)  
-------------------------------------  
C
=
= 29pF  
2
R
3
Note that C is the actual capacitance seen by the regulator,  
o
where Rc is the ESR of the output capacitor.  
Select 30pF for C . Zero f is a phase boost zero to increase the  
which may include ceramic high frequency decoupling and bulk  
output capacitors. Ceramic may have to be derated by  
approximately 40% depending on dielectric, voltage stress, and  
temperature.  
2
z2  
phase margin. Place it between f and 1/2 switching frequency.  
c
In this case, 4.7pF capacitor is selected and the zero is placed at  
f
:
z2  
Usually, a type II compensation network is used to compensate  
the peak current mode control converter. Figure 38 shows a  
typical type II compensation network and its transfer function is  
expressed in Equation 16. The frequency response is shown in  
Figure 39.  
1
(EQ. 19)  
----------------------  
f
=
= 169kHz  
z2  
2R C  
1
1
The calculated values for R , R , C , and R , C match with the  
1.8V output application in the recommended design with internal  
compensation shown in Table 1 on page 2. Do not select  
1
2
1
3
2
V
o
resistance higher than 370kΩ for R in real applications to avoid  
1
parasitic impaction.  
R
3
C
2
C
1
R1  
In practice, it is recommended to select lower resistance for  
R /R and R in the external compensation applications.  
1
2
3
Usually, 10 times lower compared with the internal  
compensation is a good start.  
V
fb  
V
comp  
R
2
V
ref  
FIGURE 38. TYPE II COMPENSATION NETWORK  
S
S
   
   
------------  
------------  
1 +  
1 +  
ˆ
v
comp  
cz1  
cz2  
(EQ. 16)  
---------------- ---------------------------------------------------------  
A S=  
=
v
ˆ
SC R  
2
v
1
o
where:  
1
1
1
--------------  
--------------  
----------------------  
=
= 2f  
=
   
= 2f  
=
f  
cz1  
z1  
cz2  
z2  
pc  
R C  
R C  
2R C  
3
2
1
1
1 2  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 16 of 19  
ISL85012  
Layout Considerations  
The layout is very important in high frequency switching  
converter design. With power devices switching efficiently at  
600kHz, the resulting current transitions from one device to  
another causing voltage spikes across the interconnecting  
impedances and parasitic circuit elements. These voltage spikes  
can degrade efficiency, radiate noise into the circuit and lead to  
device overvoltage stress. Careful component layout and printed  
circuit board design minimizes these voltage spikes.  
As an example, consider the turn-off transition of the upper  
MOSFET. Prior to turn-off, the MOSFET is carrying the full load  
current. During turn-off, current stops flowing in the MOSFET and  
is picked up by the internal body diode of the low-side MOSFET.  
Any parasitic inductance in the switched current path generates  
a large voltage spike during the switching interval. Careful  
component selection, tight layout of the critical components, and  
short, wide traces minimize the magnitude of voltage spikes.  
FIGURE 40. RECOMMENDED TOP LAYER LAYOUT  
A multilayer printed circuit board is recommended. Figures 40  
and 41 show the recommended layout of the top layer and the  
inner Layer 1 of the schematic in Figure 1 on page 1.  
1. Place the input ceramic capacitors between PVIN and GND  
pins. Put them as close to the pins as possible.  
2. A 1µF decoupling input ceramic capacitor is recommended.  
Place it as close to the VIN pin as possible.  
3. A 2.2µF decoupling ceramic capacitor is recommended for  
VDD pin. Place it as close to the VDD pin as possible.  
4. The entire inner Layer 1 is recommended to be the GND plane  
in order to reduce the noise coupling.  
5. The switching node (PHASE) plane needs to be kept away  
from the feedback network. Place the resistor divider close to  
the IC.  
FIGURE 41. SOLID GND PLANE OF INNER LAYER 1  
6. Put three to five vias on the GND pin to connect the GND plane  
of other layers for better thermal performance. This allows the  
heat to move away from the IC. Keep the vias small but not so  
small that their inside diameter prevents solder wicking  
through the holes during reflow. An 8 mil hole with 15 mil  
diameter vias are used on the evaluation board. Do not use  
“thermal relief” patterns to connect the vias. It is important to  
have a complete connection of the plated-through hole to  
each plane.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 17 of 19  
ISL85012  
Revision History The revision history provided is for informational purposes only and is believed to be accurate, but not warranted.  
Please visit our website to make sure that you have the latest revision.  
DATE  
REVISION  
FN8677.2  
CHANGE  
Mar 17, 2017  
In “Power-Good” on page 13, updated 88% to 87% and 114% to 113%.  
Updated verbiage above Equation 7.  
Updated Equations 10 and 18.  
Updated verbiage above Equations 17 (changed 60kHz to 80kHz), 18 (changed 800Ω to 800kΩ), 19 (changed  
R3 to C2).  
Updated Layout Considerations for more clarification.  
Jan 5, 2017  
Oct 3, 2016  
FN8677.1  
FN8677.0  
Updated ordering information table to remove bulk part and add tape and reel versions.  
Added Table 2 on page 2.  
Added the last two sentences in 1st paragraph in “Enable and Soft-Start” on page 11 to instruct how to use the  
EN pin.  
Initial Release  
About Intersil  
Intersil Corporation is a leading provider of innovative power management and precision analog solutions. The company's products  
address some of the largest markets within the industrial and infrastructure, mobile computing and high-end consumer markets.  
For the most updated datasheet, application notes, related documentation and related parts, please see the respective product  
information page found at www.intersil.com.  
For a listing of definitions and abbreviations of common terms used in our documents, visit: www.intersil.com/glossary.  
You can report errors or suggestions for improving this datasheet by visiting www.intersil.com/ask.  
Reliability reports are also available from our website at www.intersil.com/support  
© Copyright Intersil Americas LLC 2016-2017. All Rights Reserved.  
All trademarks and registered trademarks are the property of their respective owners.  
For additional products, see www.intersil.com/en/products.html  
Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted  
in the quality certifications found at www.intersil.com/en/support/qualandreliability.html  
Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such  
modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets 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  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 18 of 19  
ISL85012  
For the most recent package outline drawing, see L15.3.5x3.5.  
Package Outline Drawing  
L15.3.5x3.5  
15 LEAD THIN QUAD FLAT NO-LEAD PACKAGE (TQFN)  
Rev 1, 9/14  
SEE PIN 1 ID DETAIL  
10 x 0.50 BSC  
12x 0.25±0.05  
5
A
3.50  
B
0.10 M C A B  
0.05  
PIN #1  
4
1
2
3
4
5
6
M
C
INDEX AREA  
1.002  
7
2x 0.45±0.05  
0.749 BSC  
0.653 BSC  
8
9
0.10 M C A B  
3.50  
0.05  
M
C
0.258±0.05  
0.10 M C A B  
1.096  
0.05  
M
C
(2X)  
0.05 C  
15 14 13 12 11 10  
BOTTOM VIEW  
12 x 0.48±0.1  
0.05 C (2X)  
TOP VIEW  
0.15  
PACKAGE  
OUTLINE  
(12x 0.25±0.05)  
12x 0.68±0.1  
1
0.15  
(10x 0.50)  
(1.002)  
(2x 0.45±0.05)  
(0.258±0.05)  
0.37  
(0.749)  
(0.653)  
PIN 1 ID DETAIL  
(3.90)  
0.10 C  
(1.096)  
0.203 REF  
C
0.75 ±0.05  
(0.20 TYP)  
(3.90)  
SEATING  
PLANE  
-0  
+0.05  
6
15x  
0.08 C  
0.02  
SIDE VIEW  
TYPICAL RECOMMENDED LAND PATTERN  
NOTES:  
1. Dimensioning and tolerancing conform to ASME Y14.5m-1994.  
2. All dimensions are in millimeters.  
3.  
N is the total number of terminals.  
4. The location of the marked terminal #1 identifier is within the hatched area.  
Dimension applies to metallized terminal and is measured between  
0.15mm and 0.30mm from the terminal tip. If the terminal has a radius  
on the other end of it, dimension b should not be measured in that  
radius area.  
5.  
6.  
Coplanarity applies to the terminals and all other bottom surface metallization.  
FN8677 Rev.2.00  
Mar 17, 2017  
Page 19 of 19  

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