ISL6443AIVZ-TK [RENESAS]

300kHz Dual, 180° Out-of-Phase, Step-Down PWM and Single Linear Controller; QFN28, TSSOP28; Temp Range: -40° to 85°C;
ISL6443AIVZ-TK
型号: ISL6443AIVZ-TK
厂家: RENESAS TECHNOLOGY CORP    RENESAS TECHNOLOGY CORP
描述:

300kHz Dual, 180° Out-of-Phase, Step-Down PWM and Single Linear Controller; QFN28, TSSOP28; Temp Range: -40° to 85°C

开关 光电二极管
文件: 总20页 (文件大小:866K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
DATASHEET  
ISL6443A  
FN6600  
Rev 3.00  
Sep 4, 2015  
300kHz Dual, 180° Out-of-Phase, Step-Down PWM and Single Linear Controller  
The ISL6443A is a high-performance, triple-output controller  
optimized for converting wall adapter, battery or network  
Features  
• Wide Input Supply Voltage Range  
- Variable 5.6V to 24V  
intermediate bus DC input supplies into the system supply  
voltages required for a wide variety of applications. Each  
output is adjustable down to 0.8V. The two PWMs are  
synchronized at 180° out-of-phase, thus reducing the RMS  
input current and ripple voltage.  
- Fixed 4.5V to 5.6V  
• Three Independently Programmable Output Voltages  
• Switching Frequency . . . . . . . . . . . . . . . . . . . . . . .300kHz  
• Out-of-Phase PWM Controller Operation  
The ISL6443A incorporates several protection features. An  
adjustable overcurrent protection circuit monitors the output  
current by sensing the voltage drop across the lower  
MOSFET. Hiccup mode overcurrent operation protects the  
DC/DC components from damage during output  
- Reduces Required Input Capacitance and Power  
Supply Induced Loads  
• No External Current Sense Resistor  
overload/short circuit conditions. Each PWM has an  
independent logic-level shutdown input (SD1 and SD2).  
- Uses Lower MOSFET’s r  
DS(ON)  
• Bidirectional Frequency Synchronization for  
Synchronizing Multiple ISL6443As  
A single PGOOD signal is issued when soft-start is complete  
on both PWM controllers and their outputs are within 10% of  
the set point and the linear regulator output is greater than  
75% of its setpoint. Thermal shutdown circuitry turns off the  
device if the junction temperature exceeds +150°C.  
• Programmable Soft-Start  
• Extensive Circuit Protection Functions  
- PGOOD  
- UVLO  
Ordering Information  
- Overcurrent  
- Over-temperature  
PART  
NUMBER  
(Note)  
TEMP.  
RANGE  
(°C)  
PART  
MARKING  
PACKAGE  
(Pb-Free)  
PKG.  
DWG. #  
- Independent Shutdown for Both PWMs  
• Excellent Dynamic Response  
ISL6443AIRZ* 6443A IRZ -40 to +85 28 Ld 5x5 QFN L28.5x5  
- Voltage Feed-Forward with Current Mode Control  
ISL6443AIVZ* 6443A IVZ -40 to +85 28 Ld TSSOP M28.173  
• QFN Packages:  
(No longer  
available,  
- QFN - Compliant to JEDEC PUB95 MO-220  
QFN - Quad Flat No Leads - Package Outline  
recommended  
replacement:  
ISL6443AIRZ)  
- Near Chip Scale Package Footprint, which Improves  
PCB Efficiency and has a Thinner Profile  
Add “-TK” suffix for tape and reel. Please refer to TB347 for details  
on reel specifications.  
• Pb-Free (RoHS Compliant)  
NOTE: 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.  
Applications  
• Power Supplies with Multiple Outputs  
• xDSL Modems/Routers  
• DSP, ASIC, and FPGA Power Supplies  
• Set-Top Boxes  
• Dual Output Supplies for DSP, Memory, Logic, µP Core  
and I/O  
Telecom Systems  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 1 of 20  
 
ISL6443A  
Pinouts  
ISL6443A  
(28 LD QFN)  
TOP VIEW  
ISL6443A  
(28 LD TSSOP)  
TOP VIEW  
LGATE2  
BOOT2  
UGATE2  
PHASE2  
ISEN2  
1
2
3
4
5
6
7
8
9
28 LGATE1  
27 BOOT1  
26 UGATE1  
25 PHASE1  
24 ISEN1  
23 PGND  
22 SD1  
28 27 26 25 24 23 22  
PHASE2  
ISEN2  
ISEN1  
PGND  
SD1  
1
2
3
4
5
6
7
21  
20  
19  
PGOOD  
VCC_5V  
SD2  
PGOOD  
VCC_5V  
SD2  
18 SS1  
21 SS1  
SS2  
20  
SGND  
SGND  
17  
OCSET2 10  
FB2 11  
19 OCSET1  
18 FB1  
SS2  
16 OCSET1  
15  
OCSET2  
FB1  
SGND 12  
VIN 13  
17 SGND  
16 GATE3  
15 FB3  
8
9
10  
11 12 13 14  
SYNC 14  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 2 of 20  
Block Diagram  
BOOT1  
UGATE1  
PHASE1  
VCC_5V  
LGATE1  
PGND  
BOOT2  
UGATE2  
PHASE2  
VCC_5V  
LGATE2  
PGOOD SD1  
VIN SGND  
SD2  
VCC_5V  
ADAPTIVE DEAD-TIME  
V/I SAMPLE TIMING  
ADAPTIVE DEAD-TIME  
V/I SAMPLE TIMING  
POR  
PGND  
ENABLE  
0.8V REFERENCE  
BIAS SUPPLIES  
REFERENCE  
FAULT LATCH  
SOFT-START  
+
GATE3  
FB3  
+
V
E
g
*V  
E
m
-
UV  
UV  
PGOOD  
PGOOD  
18.5pF  
1400k  
18.5pF  
1400k  
VSEN2  
SOFT2  
180k  
180k  
-
FB1  
-
OC1  
OC2  
16k  
16k  
PWM1  
PWM2  
-
-
+
+
ERROR AMP 2  
+
ERROR AMP 1  
0.8V  
REF  
+
+
SS1  
+
0.8V  
REF  
DUTY CYCLE RAMP GENERATOR  
PWM CHANNEL PHASE CONTROL  
ISEN1  
ISEN2  
-
-
CURRENT  
SAMPLE  
CURRENT  
SAMPLE  
CURRENT  
SAMPLE  
CURRENT  
SAMPLE  
+
+
OCSET2  
OCSET1  
1.7V REFERENCE  
+
+
1.7V REFERENCE  
-
-
OC1  
OC2  
+
+
VIN  
VCC_5V  
SYNC  
SAME STATE FOR  
2 CLOCK CYCLES  
SAME STATE FOR  
2 CLOCK CYCLES  
REQUIRED TO LATCH  
REQUIRED TO LATCH  
OVERCURRENT FAULT  
OVERCURRENT FAULT  
 
ISL6443A  
Typical Application Schematic  
+12V  
+
C1  
56µF  
C2  
4.7µF  
VIN  
VCC_5V  
D1  
BAT54HT1  
D2  
BAT54HT1  
SS1  
SS2  
10  
4
6
18  
C4  
0.1µF  
C5  
0.1µF  
C3  
1µF  
C6  
1µF  
BOOT1  
BOOT2  
24  
27  
C7  
0.1µF  
C8  
0.1µF  
UGATE1  
PHASE1  
UGATE2  
PHASE2  
23  
22  
28  
1
L1  
R3  
L2  
VOUT1  
R4  
VOUT2  
ISEN1  
ISEN2  
21  
2
6.4µH  
+
6.4µH  
1.4k  
C9  
330µF  
+3.3V, 2A  
+1.2V, 2A  
1.4k  
C10  
330µF  
+
ISL6443A*  
LGATE1  
PGND  
LGATE2  
FB2  
25  
20  
26  
8
R5  
31.6k  
Q1  
FDS6990S  
Q2  
FDS6990S  
R1  
4.99k  
FB1  
SD1  
SGND  
SGND  
15  
9
14  
13  
R6  
10k  
R2  
10k  
19  
5
GATE3  
FB3  
C11  
0.01µF  
SD2  
VOUT2  
+3.3V  
12  
OCSET1  
OCSET2  
7
16  
R12  
100  
R8  
120k  
17 11  
3
R7  
120k  
Q3  
IRF7404  
SGND  
SYNC  
VOUT3  
PGOOD  
PGOOD  
+2.5V, 500mA  
R9  
10k  
R10  
21.5k  
C12  
10µF  
VCC_5V  
R11  
10k  
*NOTE: Pin numbers correspond to the QFN pinout.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 4 of 20  
 
ISL6443A  
Absolute Maximum Ratings  
Thermal Information  
Supply Voltage (VCC_5V Pin) . . . . . . . . . . . . . . . . . . . .-0.3V to +7V  
Thermal Resistance (Typical)  
(°C/W)  
(°C/W)  
JC  
JA  
Input Voltage (V Pin). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+27V  
BOOT1, 2 and UGATE1, 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .+35V  
PHASE1, 2 and ISEN1, 2  
. . . . . . . . . . . . . . . . . . . . .-5V (<100ns, 10µJ)/-0.3V (DC) to +27V  
BOOT1, 2 with Respect to PHASE1, 2 . . . . . . . . . . . . . . . . . . +6.5V  
UGATE1, 2. . . . . . . . . . . .(PHASE1, 2 - 0.3V) to (BOOT1, 2 + 0.3V)  
IN  
28 Lead QFN (Notes 1, 2) . . . . . . . .  
28 Lead TSSOP (Note 1) . . . . . . . . .  
36  
75  
4
NA  
Maximum Junction Temperature . . . . . . . . . . . . . . .-55°C to +150°C  
Maximum Storage Temperature Range. . . . . . . . . .-65°C to +150°C  
Temperature Range. . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C  
Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below  
http://www.intersil.com/pbfree/Pb-FreeReflow.asp  
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:  
1. is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See  
JA  
Tech Brief TB379  
2. is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.  
JA  
3. For , the “case temp” location is the center of the exposed metal pad on the package underside.  
JC  
Electrical Specifications Recommended operating conditions unless otherwise noted. Refer to “Block Diagram” on page 3 and “Typical  
Application Schematic” on page 4. V = 5.6V to 24V, or VCC_5V = 5V ±10%, T = -40°C to +85°C (Note 7),  
IN  
A
Typical values are at T = +25°C. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless  
A
otherwise specified. Temperature limits established by characterization and are not production tested.  
PARAMETER  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
VIN SUPPLY  
Input Voltage Range  
5.6  
4.5  
12  
24  
V
V
Input Voltage Range  
V
= VCC (Note 4)  
5.0  
5.6  
IN  
VCC_5V SUPPLY (Note 4)  
Input Voltage  
4.5  
4.5  
60  
5.0  
5.0  
-
5.6  
5.5  
-
V
V
Output Voltage  
V
V
> 5.6V, I = 20mA  
L
IN  
IN  
Maximum Output Current  
SUPPLY CURRENT  
= 12V  
mA  
Shutdown Current (Note 5)  
Operating Current (Note 6)  
REFERENCE SECTION  
Nominal Reference Voltage  
Reference Voltage Tolerance  
POWER-ON RESET  
SD1 = SD2 = GND  
-
-
50  
375  
4.0  
µA  
2.0  
mA  
-
0.8  
-
-
V
-1.0  
1.0  
%
Rising VCC_5V Threshold  
Falling VCC_5V Threshold  
OSCILLATOR  
4.25  
3.95  
4.45  
4.2  
4.5  
4.4  
V
V
Total Frequency Variation  
Peak-to-Peak Sawtooth Amplitude (Note 7)  
260  
300  
1.6  
0.667  
1.0  
5.0  
4.8  
-
340  
kHz  
V
V
V
= 12V  
= 5V  
-
-
IN  
IN  
-
-
V
Ramp Offset (Note 7)  
-
-
-
-
V
SYNC Input Rise/Fall Time (Note 7)  
SYNC Frequency Range  
SYNC Input HIGH Level  
SYNC Input LOW Level  
ns  
MHz  
V
4.16  
3.5  
-
5.44  
-
-
1.5  
V
FN6600 Rev 3.00  
Sep 4, 2015  
Page 5 of 20  
 
ISL6443A  
Electrical Specifications Recommended operating conditions unless otherwise noted. Refer to “Block Diagram” on page 3 and “Typical  
Application Schematic” on page 4. V = 5.6V to 24V, or VCC_5V = 5V ±10%, T = -40°C to +85°C (Note 7),  
IN  
A
Typical values are at T = +25°C. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless  
A
otherwise specified. Temperature limits established by characterization and are not production tested.  
PARAMETER  
SYNC Input Minimum Pulse Width (Note 7)  
SYNC Output HIGH Level  
TEST CONDITIONS  
MIN  
TYP  
15.0  
-
MAX  
UNITS  
ns  
-
-
-
V
- 0.6V  
V
CC  
SHUTDOWN1/SHUTDOWN2  
HIGH Level (Converter Enabled)  
LOW Level (Converter Disabled)  
PWM CONVERTERS  
Internal Pull-up (3A)  
2.0  
-
-
-
-
V
V
0.8  
Output Voltage  
-
-
0.8  
-
V
nA  
%
FB Pin Bias Current  
-
-
150  
Maximum Duty Cycle  
C
= 1000pF, T = +25°C  
93  
-
-
-
OUT  
A
Minimum Duty Cycle  
4
%
PWM CONTROLLER ERROR AMPLIFIERS  
DC Gain (Note 7)  
-
-
-
88  
15  
-
-
-
dB  
Gain-Bandwidth Product (Note 7)  
Slew Rate (Note 7)  
MHz  
V/µs  
2.0  
PWM CONTROLLER GATE DRIVERS (Note 7)  
Sink/Source Current  
-
-
-
-
-
-
-
400  
8
-
-
-
-
-
-
-
mA  
Upper Drive Pull-Up Resistance  
Upper Drive Pull-Down Resistance  
Lower Drive Pull-Up Resistance  
Lower Drive Pull-Down Resistance  
Rise Time  
VCC_5V = 4.5V  
VCC_5V = 4.5V  
VCC_5V = 4.5V  
VCC_5V = 4.5V  
3.2  
8
1.8  
18  
18  
C
C
= 1000pF  
= 1000pF  
ns  
ns  
OUT  
Fall Time  
OUT  
LINEAR CONTROLLER  
Drive Sink Current  
50  
-
-
-
mA  
V
FB3 Feedback Threshold  
I = 21mA  
0.8  
75  
45  
2
-
Undervoltage Threshold  
V
-
-
150  
-
%
FB  
FB3 Input Leakage Current  
Amplifier Transconductance  
POWER GOOD AND CONTROL FUNCTIONS  
PGOOD LOW Level Voltage  
PGOOD Leakage Current  
-
nA  
A/V  
V
= 0.8V, I = 21mA  
-
FB  
Pull-up = 100k  
-
-
0.1  
0.5  
±1.0  
120  
95  
V
µA  
%
%
%
-
-
PGOOD Upper Threshold, PWM 1 and 2  
PGOOD Lower Threshold, PWM 1 and 2  
PGOOD for Linear Controller  
ISEN AND CURRENT LIMIT  
Full Scale Input Current (Note 8)  
Overcurrent Threshold (Note 8)  
OCSET (Current Limit) Voltage  
Fraction of set point  
Fraction of set point  
105  
80  
70  
-
75  
80  
-
-
-
32  
64  
-
-
-
µA  
µA  
V
R
= 110k  
OCSET  
1.7  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 6 of 20  
ISL6443A  
Electrical Specifications Recommended operating conditions unless otherwise noted. Refer to “Block Diagram” on page 3 and “Typical  
Application Schematic” on page 4. V = 5.6V to 24V, or VCC_5V = 5V ±10%, T = -40°C to +85°C (Note 7),  
IN  
A
Typical values are at T = +25°C. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless  
A
otherwise specified. Temperature limits established by characterization and are not production tested.  
PARAMETER  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
SOFT-START  
Soft-Start Current  
PROTECTION  
-
5
-
µA  
Thermal Shutdown  
Rising  
Hysteresis  
-
-
150  
20  
-
-
°C  
°C  
NOTES:  
4. In normal operation, where the device is supplied with voltage on the V pin, the VCC_5V pin provides a 5V output capable of 60mA (min).  
IN  
When the VCC_5V pin is used as a 5V supply input, the internal LDO regulator is disabled and the V input pin must be connected to the  
IN  
VCC_5V pin. (Refer to “Pin Descriptions” on page 10 for more details.)  
5. This is the total shutdown current with V = VCC_5V = PVCC = 5V.  
IN  
6. Operating current is the supply current consumed when the device is active but not switching. It does not include gate drive current.  
7. Limits should be considered typical and are not production tested.  
8. Established by characterization. The full scale current of 32µA is recommended for optimum current sample and hold operation. See “Feedback  
Loop Compensation” on page 13.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 7 of 20  
ISL6443A  
Typical Performance Curves Oscilloscope Plots are Taken Using the ISL6443A EVAL Evaluation Board, VIN = 12V Unless  
Otherwise Noted.  
3.40  
3.39  
3.38  
3.37  
3.36  
3.35  
3.34  
3.33  
3.32  
3.31  
3.30  
3.40  
3.39  
3.38  
3.37  
3.36  
3.35  
3.34  
3.33  
3.32  
3.31  
3.30  
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5  
LOAD CURRENT (A)  
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5  
LOAD CURRENT (A)  
FIGURE 1. PWM1 LOAD REGULATION  
FIGURE 2. PWM2 LOAD REGULATION  
PGOOD 5V/DIV  
0.85  
0.84  
0.83  
0.82  
V
2V/DIV  
2V/DIV  
OUT3  
OUT2  
0.81  
0.80  
0.79  
0.78  
0.77  
V
0.76  
0.75  
V
2V/DIV  
OUT1  
60  
-40  
-20  
20  
40  
80  
0
TEMPERATURE (°C)  
FIGURE 3. REFERENCE VOLTAGE VARIATION OVER  
TEMPERATURE  
FIGURE 4. SOFT-START WAVEFORMS WITH PGOOD  
V
20mV/DIV, AC-COUPLED  
V
20mV/DIV, AC-COUPLED  
OUT2  
OUT1  
I
0.5A/DIV, AC-COUPLED  
L1  
I
0.5A/DIV, AC-COUPLED  
L2  
PHASE1 10V/DIV  
PHASE2 10V/DIV  
FIGURE 5. PWM1 WAVEFORMS  
FIGURE 6. PWM2 WAVEFORMS  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 8 of 20  
 
ISL6443A  
Typical Performance Curves Oscilloscope Plots are Taken Using the ISL6443A EVAL Evaluation Board, VIN = 12V Unless  
Otherwise Noted. (Continued)  
V
200mV/DIV  
OUT2  
AC-COUPLED  
V
200mV/DIV  
OUT1  
AC-COUPLED  
I
1A/DIV  
OUT2  
I
1A/DIV  
OUT1  
FIGURE 7. LOAD TRANSIENT RESPONSE V  
(3.3V)  
FIGURE 8. LOAD TRANSIENT RESPONSE V (3.3V)  
OUT2  
OUT1  
VCC_5V 1V/DIV  
V
2V/DIV  
OUT1  
I
L1  
2A/DIV  
SS1 2V/DIV  
V
1V/DIV  
OUT1  
FIGURE 10. OVERCURRENT HICCUP MODE OPERATION  
FIGURE 9. PWM SOFT-START WAVEFORM  
100  
90  
100  
90  
80  
80  
70  
60  
70  
60  
0
1
2
3
4
0
1
2
3
4
LOAD CURRENT (A)  
LOAD CURRENT (A)  
FIGURE 11. PWM1 EFFICIENCY vs LOAD (3.3V), V = 12V  
IN  
FIGURE 12. PWM2 EFFICIENCY vs LOAD (3.3V), V = 12V  
IN  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 9 of 20  
ISL6443A  
Pin Descriptions  
BOOT2, BOOT1 - These pins power the upper MOSFET  
drivers of each PWM converter. Connect these pins to the  
junction of the bootstrap capacitor and the cathode of the  
bootstrap diode. The anode of the bootstrap diode is  
connected to the VCC_5V pin.  
REQUIRED outputs are within regulation AND soft-start  
(SS1/SS2) is complete.  
The last case is when both of the SD1 and SD2 are LOW.  
PGOOD will be low.  
SGND - (Pin 20 on the TSSOP; Pin 17 on the QFN)  
This is the small-signal ground, common to all 3 controllers,  
and must be routed separately from the high current ground  
(PGND). All voltage levels are measured with respect to this  
pin. A small ceramic capacitor should be connected right  
next to this pin for noise decoupling.  
UGATE2, UGATE1 - These pins provide the gate drive for  
the upper MOSFETs.  
PHASE2, PHASE1 - These pins are connected to the junction  
of the upper MOSFETs source, output filter inductor and lower  
MOSFETs drain.  
LGATE2, LGATE1 - These pins provide the gate drive for  
the lower MOSFETs.  
VIN - Use this pin to power the device with an external  
supply voltage with a range of 5.6V to 24V. For 5V ±10%  
operation, connect this pin to VCC_5V.  
PGND - This pin provides the power ground connection for  
the lower gate drivers for both PWM1 and PWM2. This pin  
should be connected to the sources of the lower MOSFETs  
and the (-) terminals of the external input capacitors.  
VCC_5V - This pin is the output of the internal 5V linear  
regulator. This output supplies the bias for the IC, the low  
side gate drivers, and the external boot circuitry for the high  
side gate drivers. The IC may be powered directly from a  
single 5V (±10%) supply at this pin. When used as a 5V  
FB3, FB2, FB1 - These pins are connected to the feedback  
resistor divider and provide the voltage feedback signals for  
the respective controller. They set the output voltage of the  
converter. In addition, the PGOOD circuit uses these inputs  
to monitor the output voltage status.  
supply input, this pin must be externally connected to V  
The VCC_5V pin must be always de-coupled to power  
.
IN  
ground with a minimum of 4.7µF ceramic capacitor, placed  
very close to the pin.  
ISEN2, ISEN1 - These pins are used to monitor the voltage  
drop across the lower MOSFET for current loop feedback  
and overcurrent protection.  
SYNC - This pin may be used to synchronize two or more  
ISL6443A controllers. This pin requires a 1k resistor to  
ground if used; connect directly to VCC_5V if not used.  
PGOOD - This is an open drain logic output used to indicate  
the status of the output voltages. This pin is pulled low when  
either of the two PWM outputs is not within 10% of the  
respective nominal voltage, or if the linear controller output is  
less than 75% of it’s nominal value.  
SS1, SS2 - These pins provide a soft-start function for their  
respective PWM controllers. When the chip is enabled, the  
regulated 5µA pull-up current source charges the capacitor  
connected from this pin to ground. The error amplifier  
reference voltage ramps from 0V to 0.8V while the voltage  
on the soft-start pin ramps from 0V to 0.8V.  
Table 1 shows detailed status of PGOOD which can be  
classified into 4 cases under different combinations of SD1  
and SD2 inputs.  
SD1, SD2 - These pins provide an enable/disable function  
for their respective PWM output. The output is enabled when  
this pin is floating or pulled HIGH, and disabled when the pin  
is pulled LOW.  
The first case is when both SD1 and SD2 are HIGH.  
PGOOD will be HIGH if all FB pins from the 3 REQUIRED  
outputs are within regulation AND soft-starts (SS1 AND SS2)  
are complete.  
GATE3 - This pin is the open drain output of the linear  
regulator controller.  
The other two cases are when either of SD1 or SD2 is LOW  
which means the system wants to shut down one of the  
PWM outputs but still wants to keep another output working.  
PGOOD will be HIGH if all the FB pins from the 2  
OCSET2, OCSET1 - A resistor from this pin to ground sets  
the overcurrent threshold for the respective PWM.  
TABLE 1. DETAILED STATUS OF PGOOD  
LDO > 75%? 90% < FB1 < 110%? 90% < FB2 < 110%? SS1 COMPLETED? SS2 COMPLETED? PGOOD  
SD1  
SD2  
1
1
0
0
1
0
1
0
Y
Y
Y
x
Y
Y
x
Y
x
Y
Y
x
Y
x
1
1
1
0
Y
x
Y
x
x
x
“x” means “don’t care”.  
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ISL6443A  
main outputs at start-up. The soft-start time can be obtained  
from Equation 1:  
Functional Description  
General Description  
C
SS  
-----------  
t
= 0.8V  
SOFT  
(EQ. 1)  
The ISL6443A integrates control circuits for two synchronous  
buck converters and one linear controller. The two synchronous  
bucks operate out-of-phase to substantially reduce the input  
ripple and thus reduce the input filter requirements. The chip  
has four control lines (SS1, SD1, SS2, and SD2), which provide  
independent control for each of the synchronous buck outputs.  
5A  
VCC_5V 1V/DIV  
The buck PWM controllers employ a free-running frequency  
of 300kHz. The current mode control scheme with an input  
voltage feed-forward ramp input to the modulator provides  
excellent rejection of input voltage variations and provides  
simplified loop compensations.  
V
1V/DIV  
OUT1  
The linear controller can drive either a PNP or PFET to provide  
ultra low-dropout regulation with programmable voltages.  
SS1 1V/DIV  
Internal 5V Linear Regulator (VCC_5V)  
All ISL6443A functions are internally powered from an  
on-chip, low dropout 5V regulator. The maximum regulator  
input voltage is 24V. Bypass the regulator’s output  
(VCC_5V) with a 4.7µF capacitor to ground. The dropout  
voltage for this LDO is typically 600mV, so when VIN is  
greater than 5.6V, VCC_5V is typically 5V. The ISL6443A  
also employs an undervoltage lockout circuit that disables  
both regulators when VCC_5V falls below 4.4V.  
FIGURE 13. SOFT-START OPERATION  
The soft-start capacitors can be chosen to provide start-up  
tracking for the two PWM outputs. This can be achieved by  
choosing the soft-start capacitors such that the soft-start  
capacitor ratio equals the respective PWM output voltage  
ratio. For example, if one uses PWM1 = 1.2V and PWM2 =  
3.3V, then the soft-start capacitor ratio should be,  
C
/C  
= 1.2/3.3 = 0.364. Figure 14 shows that soft-start  
The internal LDO can source over 60mA to supply the IC,  
power the low side gate drivers and charge the external boot  
capacitor. When driving large FETs (especially at 300kHz  
frequency), little or no regulator current may be available for  
external loads.  
SS1 SS2  
waveform with C = 0.01µF and C = 0.027µF.  
SS1  
SS2  
V
1V/DIV  
For example, a single large FET with 15nC total gate charge  
requires 15nC x 300kHz = 4.5mA. Also, at higher input  
voltages with larger FETs, the power dissipation across the  
internal 5V will increase. Excessive dissipation across this  
regulator must be avoided to prevent the junction temperature  
from rising. Larger FETs can be used with 5V ±10% input  
applications. The thermal overload protection circuit will be  
triggered if the VCC_5V output is short circuited. Connect  
OUT2  
V
1V/DIV  
OUT1  
VCC_5V to V for 5V ±10% input applications.  
IN  
Soft-Start Operation  
When soft-start is initiated, the voltage on the SS pin of the  
enabled PWM channels starts to ramp gradually, due to the  
5A current sourced into the external capacitor. The output  
voltage follows the soft-start voltage.  
FIGURE 14. PWM1 AND PWM2 OUTPUT TRACKING DURING  
START-UP  
Output Voltage Programming  
A resistive divider from the output to ground sets the output  
voltage of either PWM channel. The center point of the  
divider shall be connected to FBx pin. The output voltage  
value is determined by Equation 2.  
When the SS pin voltage reaches 0.8V, the output voltage of  
the enabled PWM channel reaches the regulation point, and  
the soft-start pin voltage continues to rise. At this point the  
PGOOD and fault circuitry is enabled. This completes the  
soft-start sequence. Any further rise of SS pin voltage does  
not affect the output voltage. By varying the values of the  
soft-start capacitors, it is possible to provide sequencing of the  
(EQ. 2)  
R
+ R  
2
R
2
1
--------------------  
V
= 0.8V  
OUTx  
where R is the top resistor of the feedback divider network  
1
and R is the resistor connected from FBx to ground.  
2
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Sep 4, 2015  
Page 11 of 20  
 
 
 
ISL6443A  
the gate control logic provides adaptive dead time by  
monitoring real gate waveforms of both the upper and the lower  
MOSFETs. Shoot-through control logic provides a 20ns  
deadtime to ensure that both the upper and lower MOSFETs  
will not turn on simultaneously and cause a shoot-through  
condition.  
Out-of-Phase Operation  
The two PWM controllers in the ISL6443A operate 180o  
out-of-phase to reduce input ripple current. This reduces the  
input capacitor ripple current requirements, reduces power  
supply-induced noise and improves EMI. This effectively helps  
to lower component cost, save board space and reduce EMI.  
Gate Drivers  
Dual PWMs typically operate in-phase and turn on both upper  
FETs at the same time. The input capacitor must then support  
the instantaneous current requirements of both controllers  
simultaneously, resulting in increased ripple voltage and  
current. The higher RMS ripple current lowers the efficiency  
due to the power loss associated with the ESR of the input  
capacitor. This typically requires more low-ESR capacitors in  
parallel to minimize the input voltage ripple and ESR-related  
losses, or to meet the required ripple current rating.  
The low-side gate driver is supplied from VCC_5V and  
provides a peak sink/source current of 400mA. The high-side  
gate driver is also capable of 400mA current. Gate-drive  
voltages for the upper N-Channel MOSFET are generated by  
the flying capacitor boot circuit. A boot capacitor connected  
from the BOOT pin to the PHASE node provides power to the  
high side MOSFET driver. To limit the peak current in the IC,  
an external resistor may be placed between the UGATE pin  
and the gate of the external MOSFET. This small series  
resistor also damps any oscillations caused by the resonant  
tank of the parasitic inductances in the traces of the board and  
the FET’s input capacitance.  
With dual synchronized out-of-phase operation, the high-side  
MOSFETs of the ISL6443A turn on 180o out-of-phase. The  
instantaneous input current peaks of both regulators no longer  
overlap, resulting in reduced RMS ripple current and input  
voltage ripple. This reduces the required input capacitor ripple  
current rating, allowing fewer or less expensive capacitors, and  
reducing the shielding requirements for EMI. The “Typical  
Performance Curves Oscilloscope Plots are Taken Using the  
ISL6443A EVAL Evaluation Board, VIN = 12V Unless  
Otherwise Noted.” on page 8 show the synchronized 180° out-  
of-phase operation.  
VIN  
VCC_5V  
BOOT  
UGATE  
PHASE  
Input Voltage Range  
The ISL6443A is designed to operate from input supplies  
ranging from 4.5V to 24V. However, the input voltage range  
can be effectively limited by the available maximum duty  
ISL6443A  
cycle (D  
= 93%).  
MAX  
FIGURE 15. GATE DRIVER  
V
+ V  
d1  
0.93  
OUT  
--------------------------------  
V
=
+ V V  
d1  
(EQ. 3)  
INmin  
d2  
At start-up, the low-side MOSFET turns on and forces PHASE  
to ground in order to charge the BOOT capacitor to 5V. After the  
low-side MOSFET turns off, the high-side MOSFET is turned  
on by closing an internal switch between BOOT and UGATE.  
This provides the necessary gate-to-source voltage to turn on  
the upper MOSFET, an action that boosts the 5V gate drive  
where,  
V
= Sum of the parasitic voltage drops in the inductor  
d1  
discharge path, including the lower FET, inductor and PC  
board.  
V
= Sum of the voltage drops in the charging path,  
d2  
including the upper FET, inductor and PC board resistances.  
signal above V . The current required to drive the upper  
IN  
MOSFET is drawn from the internal 5V regulator.  
The maximum input voltage and minimum output voltage is  
limited by the minimum on-time (t  
).  
ON(min)  
Protection Circuits  
V
OUT  
300kHz  
The converter output is monitored and protected against  
overload, short circuit and undervoltage conditions. A  
sustained overload on the output sets the PGOOD low and  
initiates hiccup mode.  
---------------------------------------------------  
V
INmax  
t
(EQ. 4)  
ONmin  
where, t  
= 30ns  
ON(min)  
Gate Control Logic  
Overcurrent Protection  
The gate control logic translates generated PWM signals into  
gate drive signals, which provides amplification, level shifting  
and shoot-through protection. The gate drivers have some  
circuitry that helps optimize the ICs performance over a wide  
range of operational conditions. As MOSFET switching times  
can vary dramatically from type to type and with input voltage,  
Both PWM controllers use the lower MOSFET’s ON-resistance,  
r
, to monitor the current in the converter. The sensed  
DS(ON)  
voltage drop is compared with a threshold set by a resistor  
connected from the OCSETx pin to ground.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 12 of 20  
ISL6443A  
Feedback Loop Compensation  
(EQ. 5)  
7R  
CS  
R
= ----------------------------------------  
OCSET  
To reduce the number of external components and to simplify  
the process of determining compensation components, both  
PWM controllers have internally compensated error  
amplifiers. To make internal compensation possible, several  
design measures were taken.  
I r  
OC DSon  
where, I  
OC  
is the desired overcurrent protection threshold,  
and R is a value of the current sense resistor connected to  
CS  
the ISENx pin. If an overcurrent is detected for 2 consecutive  
clock cycles, then the IC enters a hiccup mode by turning off  
the gate drivers and entering into soft-start. The IC will cycle  
2x through soft-start before trying to restart. The IC will  
continue to cycle through soft-start until the overcurrent  
condition is removed. Hiccup mode is active during soft-start,  
so care must be taken to ensure that the peak inductor current  
does not exceed the overcurrent threshold during soft-start.  
First, the ramp signal applied to the PWM comparator is  
proportional to the input voltage provided via the VIN pin.  
This keeps the modulator gain constant with variation in the  
input voltage. Second, the load current proportional signal is  
derived from the voltage drop across the lower MOSFET  
during the PWM time interval and is subtracted from the  
amplified error signal on the comparator input. This creates  
an internal current control loop. The resistor connected to  
the ISEN pin sets the gain in the current feedback loop.  
Equation 6 estimates the required value of the current sense  
resistor depending on the maximum operating load current  
Because of the nature of this current sensing technique, and  
to accommodate a wide range of r  
variations, the  
DS(ON)  
value of the overcurrent threshold should represent an  
overload current about 150% to 180% of the maximum  
operating current. If more accurate current protection is  
desired, place a current sense resistor in series with the  
lower MOSFET source.  
and the value of the MOSFET’s r  
.
DS(ON)  
I  
r  
MAX DSON  
----------------------------------------------  
R
(EQ. 6)  
CS  
32A  
Over-Temperature Protection  
Choosing R  
to provide 32µA of current to the current  
CS  
The IC incorporates an over-temperature protection circuit  
that shuts the IC down when a die temperature of +150°C  
is reached. Normal operation resumes when the die  
temperatures drops below +130°C through the initiation of  
a full soft-start cycle.  
sample and hold circuitry is recommended but values down  
to 2µA and up to 100µA can be used.  
Due to the current loop feedback, the modulator has a single  
pole response with -20dB slope at a frequency determined  
by the load.  
Implementing Synchronization  
1
The SYNC pin may be used to synchronize two or more  
controllers. When the SYNC pins of two controllers are  
connected together, one controller becomes the master and  
the other controller synchronizes to the master. A pull-down  
resistor is required and must be sized to provide a low  
enough time constant to pass the SYNC pulse. Connect this  
pin to VCC_5V if not used. Figure 16 shows the SYNC pin  
waveform operating at 16x the switching frequency.  
--------------------------------  
F
=
(EQ. 7)  
PO  
2  R C  
O
O
where R is load resistance and C is load capacitance. For  
this type of modulator, a Type 2 compensation circuit is  
usually sufficient.  
O
O
Figure 17 shows a Type 2 amplifier and its response along  
with the responses of the current mode modulator and the  
converter. The Type 2 amplifier, in addition to the pole at  
origin, has a zero-pole pair that causes a flat gain region at  
frequencies in between the zero and the pole.  
1
F
= ------------------------------ = 6kHz  
Z
(EQ. 8)  
2  R C  
2
1
1
F
= ------------------------------ = 600kHz  
2  R C  
P
(EQ. 9)  
1
2
FIGURE 16. SYNC WAVEFORM  
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Sep 4, 2015  
Page 13 of 20  
 
 
ISL6443A  
rise above its set point. Care must be taken to ensure that  
the feedback resistor’s current exceeds the pass transistors  
leakage current over the entire temperature range.  
C2  
C1  
R2  
CONVERTER  
R1  
The linear regulator output can be supplied by the output of  
one of the PWMs. When using a PFET, the output of the  
linear regulator will track the PWM supply after the PWM  
output rises to a voltage greater than the threshold of the  
PFET pass device. The voltage differential between the  
PWM and the linear output will be the load current times the  
EA  
TYPE 2 EA  
G
= 17.5dB  
M
G
= 18dB  
EA  
MODULATOR  
r
. Figure 18 shows the linear regulator (2.5V) start-up  
F
DS(ON)  
waveform and the PWM (3.3V) start-up waveform.  
F
Z
P
F
PO  
F
C
FIGURE 17. FEEDBACK LOOP COMPENSATION  
V
1V/DIV  
1V/DIV  
OUT2  
The zero frequency, the amplifier high-frequency gain, and  
the modulator gain are chosen to satisfy most typical  
applications. The crossover frequency will appear at the  
point where the modulator attenuation equals the amplifier  
high frequency gain. The only task that the system designer  
has to complete is to specify the output filter capacitors to  
position the load main pole somewhere within one decade  
lower than the amplifier zero frequency. With this type of  
compensation plenty of phase margin is easily achieved due  
to zero-pole pair phase ‘boost’.  
V
OUT3  
Conditional stability may occur only when the main load pole  
is positioned too much to the left side on the frequency axis  
due to excessive output filter capacitance. In this case, the  
ESR zero placed within the 1.2kHz to 30kHz range gives  
some additional phase ‘boost’. Some phase boost can also  
FIGURE 18. LINEAR REGULATOR START-UP WAVEFORM  
60  
50  
be achieved by connecting capacitor C in parallel with the  
Z
upper resistor R of the divider that sets the output voltage  
value. Please refer to “Output Inductor Selection” and  
“Output Capacitor Selection” on page 16 for further details.  
1
40  
30  
20  
Linear Regulator  
The linear regulator controller is a transconductance  
amplifier with a nominal gain of 2A/V. The N-Channel  
MOSFET output device can sink a minimum of 50mA. The  
reference voltage is 0.8V. With 0V differential at it’s input, the  
controller sinks 21mA of current. An external PNP transistor  
or PFET pass element can be used. The dominant pole for  
the loop can be placed at the base of the PNP (or gate of the  
PFET), as a capacitor from emitter to base (source to gate of  
a PFET). Better load transient response is achieved,  
however, if the dominant pole is placed at the output, with a  
capacitor to ground at the output of the regulator.  
10  
0
0.84  
0.79  
0.80  
0.82  
0.83  
0.85  
0.81  
FEEDBACK VOLTAGE (V)  
FIGURE 19. LINEAR CONTROLLER GAIN  
Base-Drive Noise Reduction  
The high-impedance base driver is susceptible to system  
noise, especially when the linear regulator is lightly loaded.  
Capacitively coupled switching noise or inductively coupled  
EMI onto the base drive causes fluctuations in the base  
current, which appear as noise on the linear regulator’s  
output. Keep the base drive traces away from the step-down  
converter, and as short as possible, to minimize noise  
coupling. A resistor in series with the gate drivers reduces  
the switching noise generated by PWM. Additionally, a  
Under no-load conditions, leakage currents from the pass  
transistors supply the output capacitors, even when the  
transistor is off. Generally this is not a problem since the  
feedback resistor drains the excess charge. However,  
charge may build up on the output capacitor making V  
LDO  
FN6600 Rev 3.00  
Sep 4, 2015  
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ISL6443A  
bypass capacitor may be placed across the base-to-emitter  
resistor. This bypass capacitor, in addition to the transistor’s  
input capacitor, could bring in a second pole that will  
destabilize the linear regulator. Therefore, the stability  
requirements determine the maximum base-to-emitter  
capacitance.  
7. Place the gate drive components BOOT diode and BOOT  
capacitors together near controller IC  
8. The output capacitors should be placed as close to the  
load as possible. Use short wide copper regions to  
connect output capacitors to load to avoid inductance and  
resistances.  
9. Use copper filled polygons or wide but short trace to  
connect the junction of upper FET, lower FET and output  
inductor. Also keep the PHASE node connection to the IC  
short. It is unnecessary to oversize the copper islands for  
PHASE node. Since the phase nodes are subjected to  
very high dv/dt voltages, the stray capacitor formed  
between these islands and the surrounding circuitry will  
tend to couple switching noise.  
Layout Guidelines  
Careful attention to layout requirements is necessary for  
successful implementation of a ISL6443A based DC/DC  
converter. The ISL6443A switches at a very high frequency  
and therefore the switching times are very short. At these  
switching frequencies, even the shortest trace has  
significant impedance. Also the peak gate drive current rises  
significantly in extremely short time. Transition speed of the  
current from one device to another causes voltage spikes  
across the interconnecting impedances and parasitic circuit  
elements. These voltage spikes can degrade efficiency,  
generate EMI, increase device overvoltage stress and  
ringing. Careful component selection and proper PC board  
layout minimizes the magnitude of these voltage spikes.  
10. Route all high speed switching nodes away from the  
control circuitry.  
11. Create a separate small analog ground plane near the IC.  
Connect the SGND pin to this plane. All small signal  
grounding paths, including feedback resistors, current  
limit setting resistors, and SYNC/SDx pull-down resistors  
should be connected to this SGND plane.  
12. Ensure the feedback connection to the output capacitor is  
short and direct.  
There are two sets of critical components in a DC/DC  
converter using the ISL6443A. The switching power  
components and the small signal components. The  
switching power components are the most critical from a  
layout point of view because they switch a large amount of  
energy so they tend to generate a large amount of noise.  
The critical small signal components are those connected to  
sensitive nodes or those supplying critical bias currents. A  
multi-layer printed circuit board is recommended.  
Component Selection Guidelines  
MOSFET Considerations  
The logic level MOSFETs are chosen for optimum efficiency  
given the potentially wide input voltage range and output  
power requirements. Two N-Channel MOSFETs are used in  
each of the synchronous-rectified buck converters for the  
PWM1 and PWM2 outputs. These MOSFETs should be  
Layout Considerations  
selected based upon r  
, gate supply requirements,  
DS(ON)  
1. The Input capacitors, Upper FET, Lower FET, Inductor  
and Output capacitor should be placed first. Isolate these  
power components on the topside of the board with their  
ground terminals adjacent to one another. Place the input  
high frequency decoupling ceramic capacitor very close  
to the MOSFETs.  
and thermal management considerations.  
The power dissipation includes two loss components;  
conduction loss and switching loss. These losses are  
distributed between the upper and lower MOSFETs according  
to duty cycle (see Equations 10 and 11). The conduction  
losses are the main component of power dissipation for the  
lower MOSFETs. Only the upper MOSFET has significant  
switching losses, since the lower device turns on and off into  
near zero voltage. Equations 10 and 11 assume linear  
voltage-current transitions and do not model power loss due  
to the reverse-recovery of the lower MOSFET’s body diode.  
2
2. Use separate ground planes for power ground and small  
signal ground. Connect the SGND and PGND together  
close to the IC. Do not connect them together anywhere  
else.  
3. The loop formed by Input capacitor, the top FET and the  
bottom FET must be kept as small as possible.  
4. Ensure the current paths from the input capacitor to the  
MOSFET, to the output inductor and output capacitor are  
as short as possible with maximum allowable trace  
widths.  
I r  
V  
I V t  
F  
SW  
O
DSON  
OUT  
O
IN SW  
P
= -------------------------------------------------------------- + -----------------------------------------------------------  
UPPER  
V
2
IN  
(EQ.10)  
2
5. Place The PWM controller IC close to lower FET. The  
LGATE connection should be short and wide. The IC can  
be best placed over a quiet ground area. Avoid switching  
ground loop current in this area.  
I r  
V V  
OUT  
O
DSON  
IN  
(EQ.11)  
P
= ------------------------------------------------------------------------------  
LOWER  
V
IN  
A large gate-charge increases the switching time, t  
,
SW  
which increases the upper MOSFET switching losses.  
Ensure that both MOSFETs are within their maximum  
junction temperature at high ambient temperature by  
6. Place VCC_5V bypass capacitor very close to VCC_5V  
pin of the IC and connect its ground to the PGND plane.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 15 of 20  
 
 
ISL6443A  
calculating the temperature rise according to package  
thermal-resistance specifications.  
Use only specialized low-ESR capacitors intended for  
switching-regulator applications at 300kHz for the bulk  
capacitors. In most cases, multiple small-case electrolytic  
capacitors perform better than a single large-case capacitor.  
Output Capacitor Selection  
The output capacitors for each output have unique  
requirements. In general, the output capacitors should be  
selected to meet the dynamic regulation requirements  
including ripple voltage and load transients. Selection of  
output capacitors is also dependent on the output inductor,  
so some inductor analysis is required to select the output  
capacitors.  
The stability requirement on the selection of the output  
capacitor is that the ‘ESR zero’ (f ) be between 1.2kHz and  
Z
30kHz. This range is set by an internal, single compensation  
zero at 6kHz. The ESR zero can be a factor of five on either  
side of the internal zero and still contribute to increased  
phase margin of the control loop. Therefore,  
1
C
= ------------------------------------  
One of the parameters limiting the converter’s response to a  
load transient is the time required for the inductor current to  
slew to it’s new level. The ISL6443A will provide either 0% or  
93% duty cycle in response to a load transient.  
OUT  
2ESRf   
(EQ.14)  
Z
In conclusion, the output capacitors must meet three criteria:  
1. They must have sufficient bulk capacitance to sustain the  
output voltage during a load transient while the output  
inductor current is slewing to the value of the load  
transient.  
The response time is the time interval required to slew the  
inductor current from an initial current value to the load  
current level. During this interval the difference between the  
inductor current and the transient current level must be  
supplied by the output capacitor(s). Minimizing the response  
time can minimize the output capacitance required. Also, if  
the load transient rise time is slower than the inductor  
response time, as in a hard drive or CD drive, it reduces the  
requirement on the output capacitor.  
2. The ESR must be sufficiently low to meet the desired  
output voltage ripple due to the output inductor current.  
3. The ESR zero should be placed, in a rather large range,  
to provide additional phase margin.  
The recommended output capacitor value for the ISL6443A  
is between 150µF to 680µF, to meet stability criteria with  
external compensation. Use of aluminum electrolytic,  
POSCAP, or tantalum type capacitors is recommended. Use  
of low ESR ceramic capacitors is possible but would take  
more rigorous loop analysis to ensure stability.  
The maximum capacitor value required to provide the full,  
rising step, transient load current during the response time of  
the inductor is:  
2
L I  
TRAN  
O
C
= ----------------------------------------------------------  
OUT  
2V V DV   
OUT  
Output Inductor Selection  
(EQ.12)  
IN  
O
The PWM converters require output inductors. The output  
inductor is selected to meet the output voltage ripple  
requirements. The inductor value determines the converter’s  
ripple current and the ripple voltage is a function of the ripple  
current and output capacitor(s) ESR. The ripple voltage  
expression is given in “Output Capacitor Selection” on  
page 16 and the ripple current is approximated by  
Equation 15:  
where, C  
OUT  
is the output capacitor(s) required, L is the  
O
output inductor, I  
is the transient load current step, V  
TRAN  
is the input voltage, V is output voltage, and DV  
IN  
is the  
O
OUT  
drop in output voltage allowed during the load transient.  
High frequency capacitors initially supply the transient  
current and slow the load rate-of-change seen by the bulk  
capacitors. The bulk filter capacitor values are generally  
determined by the ESR (Equivalent Series Resistance) and  
voltage rating requirements as well as actual capacitance  
requirements.  
V V  
V  
OUT  
IN  
OUT  
I = ---------------------------------------------------------  
L
f LV  
IN  
(EQ.15)  
S
For the ISL6443A, inductor values between 6.4µH to 10µH  
are recommended when using the “Typical Application  
Schematic” on page 4. Other values can be used but a  
thorough stability study should be done.  
The output voltage ripple is due to the inductor ripple current  
and the ESR of the output capacitors as defined by  
Equation 13:  
V
= I ESR  
L
(EQ.13)  
RIPPLE  
where, I is calculated in “Output Inductor Selection” on  
L
page 16.  
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  
circuitry for specific decoupling requirements.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 16 of 20  
 
 
 
 
ISL6443A  
Input Capacitor Selection  
5.0  
4.5  
4.0  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
The important parameters for the bulk input capacitor(s) are  
the voltage rating and the RMS current rating. For reliable  
operation, select bulk input capacitors with voltage and  
current ratings above the maximum input voltage and largest  
RMS current required by the circuit. The capacitor voltage  
rating should be at least 1.25x greater than the maximum  
input voltage and 1.5x is a conservative guideline. The AC  
RMS Input current varies with the load. The total RMS  
current supplied by the input capacitance is:  
IN-PHASE  
OUT-OF-PHASE  
5V  
3.3V  
2
2
I
=
I
+ I  
(EQ.16)  
RMS  
RMS1  
RMS2  
0
1
2
3
4
5
where,  
3.3V AND 5V LOAD CURRENT  
2
I
=
DC DC I  
(EQ.17)  
RMSx  
O
FIGURE 20. INPUT RMS CURRENT vs LOAD  
DC is duty cycle of the respective PWM.  
Use a mix of input bypass capacitors to control the voltage  
ripple across the MOSFETs. Use ceramic capacitors for the  
high frequency decoupling and bulk capacitors to supply the  
RMS current. Small ceramic capacitors can be placed very  
close to the upper MOSFET to suppress the voltage induced  
in the parasitic circuit impedances.  
Depending on the specifics of the input power and its  
impedance, most (or all) of this current is supplied by the  
input capacitor(s). Figure 20 shows the advantage of having  
the PWM converters operating out-of-phase. If the  
converters were operating in-phase, the combined RMS  
current would be the algebraic sum, which is a much larger  
value as shown. The combined out-of-phase current is the  
square root of the sum of the square of the individual  
reflected currents and is significantly less than the combined  
in-phase current.  
For board designs that allow through-hole components, the  
Sanyo OS-CON® series offer low ESR and good  
temperature performance. For surface mount designs, solid  
tantalum capacitors can be used, but caution must be  
exercised with regard to the capacitor surge current rating.  
These capacitors must be capable of handling the  
surge-current at power-up. The TPS series available from  
AVX is surge-current tested.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 17 of 20  
 
ISL6443A  
Revision History  
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to the web to make sure that  
you have the latest revision.  
DATE  
REVISION  
CHANGE  
September 4, 2015  
FN6600.3  
Updated Ordering Information table on page 1.  
Added Revision History and About Intersil sections.  
Updated Package Outline Drawing M28.173 to the latest revision.  
-Rev 0 to Rev 1 changes - Convert to new POD format by moving dimensions from table onto drawing  
and adding land pattern. No dimension changes.  
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.  
You may 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 2007-2015. 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  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 18 of 20  
ISL6443A  
Package Outline Drawing  
L28.5x5  
28 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE  
Rev 2, 10/07  
4X  
3.0  
5.00  
0.50  
24X  
A
6
B
PIN #1 INDEX AREA  
28  
22  
6
PIN 1  
INDEX AREA  
1
21  
3 .10 ± 0 . 15  
15  
7
(4X)  
0.15  
8
14  
0.10 M C A B  
- 0.07  
TOP VIEW  
28X 0.55 ± 0.10  
BOTTOM VIEW  
4
28X 0.25  
+ 0.05  
SEE DETAIL "X"  
C
0.10  
0 . 90 ± 0.1  
C
BASE PLANE  
SEATING PLANE  
0.08  
C
( 4. 65 TYP )  
(
( 24X 0 . 50)  
SIDE VIEW  
3. 10)  
(28X 0 . 25 )  
( 28X 0 . 75)  
5
C
0 . 2 REF  
0 . 00 MIN.  
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 AMSE Y14.5m-1994.  
3.  
Unless otherwise specified, tolerance : Decimal ± 0.05  
4. Dimension b applies to the metallized terminal and is measured  
between 0.15mm and 0.30mm 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.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 19 of 20  
ISL6443A  
Package Outline Drawing  
M28.173  
28 LEAD THIN SHRINK SMALL OUTLINE PACKAGE (TSSOP)  
Rev 1, 5/10  
A
1
3
9.70± 0.10  
SEE DETAIL "X"  
15  
28  
6.40  
PIN #1  
I.D. MARK  
4.40 ± 0.10  
2
3
0.20 C B A  
1
14  
+0.05  
-0.06  
0.15  
B
0.65  
TOP VIEW  
END VIEW  
1.00 REF  
H
-
0.05  
+0.15  
-0.10  
0.90  
C
GAUGE  
PLANE  
1.20 MAX  
0.25  
SEATING PLANE  
0.10 C  
+0.05  
-0.06  
0.25  
0.10  
0°-8°  
0.60 ±0.15  
5
0.05 MIN  
0.15 MAX  
C B A  
M
SIDE VIEW  
DETAIL "X"  
(1.45)  
NOTES:  
1. Dimension does not include mold flash, protrusions or gate burrs.  
Mold flash, protrusions or gate burrs shall not exceed 0.15 per side.  
2. Dimension does not include interlead flash or protrusion. Interlead  
flash or protrusion shall not exceed 0.25 per side.  
3. Dimensions are measured at datum plane H.  
(5.65)  
4. Dimensioning and tolerancing per ASME Y14.5M-1994.  
5. Dimension does not include dambar protrusion. Allowable protrusion  
shall be 0.08mm total in excess of dimension at maximum material  
condition. Minimum space between protrusion and adjacent lead  
is 0.07mm.  
(0.35 TYP)  
(0.65 TYP)  
TYPICAL RECOMMENDED LAND PATTERN  
6. Dimension in ( ) are for reference only.  
7. Conforms to JEDEC MO-153.  
FN6600 Rev 3.00  
Sep 4, 2015  
Page 20 of 20  

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