ISL6530EVAL2 [INTERSIL]

Dual 5V Synchronous Buck Pulse-Width Modulator (PWM) Controller for DDRAM Memory VDDQ and VTT Termination; 5V双路同步降压型脉宽调制器(PWM )控制器,用于DDRAM内存VDDQ和VTT终端
ISL6530EVAL2
型号: ISL6530EVAL2
厂家: Intersil    Intersil
描述:

Dual 5V Synchronous Buck Pulse-Width Modulator (PWM) Controller for DDRAM Memory VDDQ and VTT Termination
5V双路同步降压型脉宽调制器(PWM )控制器,用于DDRAM内存VDDQ和VTT终端

动态存储器 双倍数据速率 控制器
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ISL6530  
®
Data Sheet  
November 15, 2004  
FN9052.2  
Dual 5V Synchronous Buck Pulse-Width  
Modulator (PWM) Controller for DDRAM  
Features  
• Provides V  
channel DDRAM memory systems  
, V  
, and V voltages for one- and two-  
TT  
DDQ REF  
Memory V  
and V Termination  
DDQ  
TT  
The ISL6530 provides complete control and protection for  
dual DC-DC converters optimized for high-performance  
DDRAM memory applications. It is designed to drive low  
cost N-channel MOSFETs in synchronous-rectified buck  
• Excellent voltage regulation  
- V  
- V  
= 2.5V ±2% over full operating range  
DDQ  
= (V  
÷2) ±1% over full operating range  
± 30mV  
REF  
DDQ  
- V = V  
TT REF  
topology to efficiently generate 2.5V V  
for powering  
DDQ  
for DDRAM differential signalling,  
• Supports ‘S3’ sleep mode  
- V is held at V ÷2 via low power window regulator  
DDRAM memory, V  
REF  
and V for signal termination. The ISL6530 integrates all of  
TT  
TT DDQ  
to minimize wake-up time  
the control, output adjustment, monitoring and protection  
functions into a single package.  
• Fast transient response  
- Full 0% to 100% duty ratio  
The V  
DDQ  
output of the converter is maintained at 2.5V  
through an integrated precision voltage reference. The V  
output is precisely regulated to 1/2 the memory power  
supply, with a maximum tolerance of ±1% over temperature  
REF  
• Operates from +5V input  
• Overcurrent fault monitor on VDD  
- Does not require extra current sensing element  
and line voltage variations. V accurately tracks V  
.
TT REF  
- Uses MOSFET’s r  
DS(ON)  
During V2_SD sleep mode, the V output is maintained by  
TT  
a low power window regulator.  
• Drives inexpensive N-Channel MOSFETs  
The ISL6530 provides simple, single feedback loop, voltage-  
mode control with fast transient response. It includes two  
phase-locked 300kHz triangle-wave oscillators which are  
• Small converter size  
- 300kHz fixed frequency oscillator  
o
• 24 Lead, SOIC or 32 Lead, 5mm×5mm QFN  
Pb-Free Available (RoHS Compliant)  
displaced 90 to minimize interference between the two  
PWM regulators. The regulators feature error amplifiers with  
a 15MHz gain-bandwidth product and 6V/µs slew rate which  
enables high converter bandwidth for fast transient  
performance. The resulting PWM duty ratio ranges from 0%  
to 100%.  
Applications  
• V  
, V , and VREF regulation for DDRAM memory  
DDQ TT  
systems  
The ISL6530 protects against over-current conditions by  
inhibiting PWM operation. The ISL6530 monitors the current  
- Main Memory in AMD® Athlon™ and K8™, Pentium®  
III, Pentium IV, Transmeta, PowerPC™, AlphaPC™, and  
UltraSparc® based computer systems  
in the V  
regulator by using the r  
of the upper  
DDQ  
DS(ON)  
- Video memory in graphics systems  
MOSFET which eliminates the need for a current sensing  
resistor.  
• High-power tracking DC-DC regulators  
Ordering Information  
TEMP  
RANGE( C)  
PKG.  
DWG. #  
o
PART NUMBER  
PACKAGE  
ISL6530CB*  
0 to 70  
24 Lead SOIC  
M24.3  
ISL6530CBZ*  
(See Note)  
0 to 70  
24 Lead SOIC  
(Pb-free)  
M24.3  
ISL6530CR*  
0 to 70  
0 to 70  
32 Lead 5x5 QFN L32.5x5  
ISL6530CRZ*  
(See Note)  
32 Lead 5x5 QFN L32.5x5  
(Pb-free)  
ISL6530EVAL1, 2  
Evaluation Board  
* Add “-T” suffix for tape and reel option.  
NOTE: Intersil Pb-free products employ special Pb-free material sets; molding  
compounds/die attach materials and 100% matte tin plate termination finish, which are  
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-020C.  
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.  
1
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.  
Copyright © Intersil Americas Inc. 2003, 2004. All Rights Reserved.  
All other trademarks mentioned are the property of their respective owners.  
ISL6530  
Pinouts  
24 LEAD (SOIC)  
32 LEAD (QFN)  
TOP VIEW  
TOP VIEW  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
14  
13  
1
2
PGND1  
LGATE1  
PVCC1  
OCSET/SD  
V2_SD  
PGOOD  
COMP2  
SENSE2  
FB2  
UGATE1  
BOOT1  
PHASE1  
VREF  
3
32 31 30 29 28 27 26 25  
4
PHASE 1  
PVCC1  
OCSET/SD  
V2_SD  
PGOOD  
COMP2  
SENSE2  
FB2  
1
2
3
4
5
6
7
8
24  
23  
22  
21  
20  
19  
18  
17  
FB1  
5
VREF  
FB1  
6
COMP1  
SENSE1  
VREF_IN  
GNDA  
7
8
COMP1  
SENSE1  
VREF_IN  
GNDA  
9
10  
11  
VCC  
PHASE2  
BOOT2  
LGATE2  
PGND2  
UGATE2 12  
GNDA  
VCC  
9
10 11 12 13 14 15 16  
FN9052.2  
2
November 15, 2004  
ISL6530  
Block Diagram  
OCSET/SD  
VCC  
PGOOD  
POWER-ON  
RESET (POR)  
+
-
SOFT-  
START  
BOOT1  
40µA  
OVER-  
CURRENT  
UGATE1  
PHASE1  
PWM  
ERROR  
AMP  
COMPARATOR  
GATE  
CONTROL  
LOGIC  
INHIBIT  
PWM  
+
+
-
-
FB1  
PVCC1  
COMP1  
0.8V  
REFERENCE  
LGATE1  
SENSE1  
VREF_IN  
OSCILLATOR  
PGND1  
BOOT2  
+
-
VREF  
o
90 Phase  
Shift  
ERROR  
AMP  
UGATE2  
+
-
FB2  
PWM  
GATE  
CONTROL  
LOGIC  
-
+
COMP2  
PHASE2  
INHIBIT  
PWM  
COMPARATOR  
VCC  
WINDOW  
SENSE2  
V2_SD  
REGULATOR  
LGATE2  
PGND2  
GND  
FN9052.2  
November 15, 2004  
3
ISL6530  
Typical Application  
+5V  
PGOOD  
R
OCSET  
D
BOOT1  
VCC  
PGOOD  
BOOT1  
OCSET/SD  
Q
RESET  
1
UGATE1  
C
BOOT1  
GNDA  
V
DDQ  
PHASE1  
L
OUT1  
+5V  
C
OUT1  
PVCC1  
Q
V2_SD  
SLEEP  
2
LGATE1  
VREF_IN  
PGND1  
V
REF  
(.5xV  
ISL6530  
)
DDQ  
VREF  
D
BOOT2  
COMP1  
BOOT2  
Q
Q
3
UGATE2  
C
BOOT2  
PHASE2  
LGATE2  
V
TT  
L
FB1  
OUT2  
4
C
OUT2  
R
FB1  
SENSE1  
COMP2  
PGND2  
SENSE2  
FB2  
R
FB2  
FIGURE 1. TYPICAL APPLICATION FOR ISL6530  
FN9052.2  
November 15, 2004  
4
ISL6530  
Absolute Maximum Ratings  
Thermal Information  
o
o
Supply Voltage, V  
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7.0V  
Thermal Resistance  
θ
( C/W)  
θ
( C/W)  
CC  
JA  
JC  
Boot Voltage, V  
Input, Output or I/O Voltage . . . . . . . . . . . .GND -0.3V to V  
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2  
- V  
. . . . . . . . . . . . . . . . . . . . . . +7.0V  
+0.3V  
BOOTn  
PHASEn  
SOIC Package (Note 1) . . . . . . . . . . . .  
QFN Package (Note 2). . . . . . . . . . . . .  
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 150 C  
Maximum Storage Temperature Range. . . . . . . . . . -65 C to 150 C  
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300 C  
65  
33  
N/A  
4
CC  
o
o
o
o
Operating Conditions  
(SOIC - Lead tips only)  
For Recommended soldering conditions see Tech Brief TB389.  
Supply Voltage, V  
CC  
Ambient Temperature Range. . . . . . . . . . . . . . . . . . . . . 0 C to 70 C  
Junction Temperature Range. . . . . . . . . . . . . . . . . . . . 0 C to 125 C  
. . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±10%  
o
o
o
o
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the  
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.  
NOTE:  
1. θ is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.  
JA  
2. θ is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. θ  
the  
JA  
JC,  
“case temp” is measured at the center of the exposed metal pad on the package underside. See Tech Brief TB379.  
Electrical Specifications Recommended Operating Conditions with Vcc = 5V, Unless Otherwise Noted  
PARAMETER  
VCC SUPPLY CURRENT  
Nominal Supply  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
I
OCSET/SD = V  
;
CC  
-
5
-
mA  
CC  
UGATE1, UGATE2, LGATE1, and LGATE2  
Open  
Shutdown Supply  
OCSET/SD = 0V  
-
3
-
mA  
POWER-ON RESET  
Rising V  
Threshold  
Threshold  
V
V
= 4.5V  
= 4.5V  
4.25  
3.75  
-
-
4.5  
4.0  
V
V
CC  
OCSET/SD  
OCSET/SD  
Falling V  
CC  
OSCILLATOR  
Free Running Frequency  
REFERENCES  
V
= 5  
275  
300  
325  
kHz  
CC  
%SENSE1  
Reference Voltage  
(V2 Error Amp Reference)  
V
SENSE1 = 2.5V  
49.5  
50  
-
50.5  
VREF  
V1 Error Amp Reference Voltage  
Tolerance  
-
-
2
-
%
V1 Error Amp Reference  
ERROR AMPLIFIERS  
DC Gain  
V
V
= 5  
CC  
0.8  
V
REF  
-
-
-
82  
15  
6
-
-
-
dB  
Gain-Bandwidth Product  
Slew Rate  
GBW  
SR  
MHz  
V/µs  
COMP = 10pF  
WINDOW REGULATOR  
Load Current  
-
-
±10  
±7  
-
mA  
%
Output Voltage Error  
V2_SD = VCC; ±10mA load on V2  
GATE DRIVERS  
Upper Gate Source (UGATE1 and 2)  
Upper Gate Sink (UGATE1 and 2)  
Lower Gate Source (LGATE1 and 2)  
Lower Gate Sink (LGATE1 and 2)  
PROTECTION  
I
V
V
V
V
= 5V, V  
= 2.5V  
-
-
-
-
-1  
1
-
-
-
-
A
A
A
A
UGATE  
CC  
UGATE-PHASE  
= 5V, V  
UGATE  
= 2.5V  
= 2.5V  
I
UGATE  
I
-1  
2
LGATE  
CC  
LGATE  
= 2.5V  
I
LGATE  
LGATE  
OCSET/SD Current Source  
OCSET/SD Disable Voltage  
I
V
= 4.5VDC  
34  
-
40  
46  
-
µA  
OCSET  
OCSET  
V
0.8  
V
RESET  
FN9052.2  
5
November 15, 2004  
ISL6530  
Functional Pin Description  
24 LEAD (SOIC)  
32 LEAD (QFN)  
TOP VIEW  
TOP VIEW  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
14  
13  
1
2
PGND1  
LGATE1  
PVCC1  
OCSET/SD  
V2_SD  
PGOOD  
COMP2  
SENSE2  
FB2  
UGATE1  
BOOT1  
PHASE1  
VREF  
3
32 31 30 29 28 27 26 25  
4
PHASE 1  
PVCC1  
OCSET/SD  
V2_SD  
PGOOD  
COMP2  
SENSE2  
FB2  
1
2
3
4
5
6
7
8
24  
23  
22  
21  
20  
19  
18  
17  
FB1  
5
VREF  
FB1  
6
COMP1  
SENSE1  
VREF_IN  
GNDA  
7
8
COMP1  
SENSE1  
VREF_IN  
GNDA  
9
10  
11  
VCC  
PHASE2  
BOOT2  
LGATE2  
PGND2  
UGATE2 12  
GNDA  
VCC  
9
10 11 12 13 14 15 16  
(r  
) set the V  
converter over-current (OC) trip  
DDQ  
BOOT1 and BOOT2  
DS(ON)  
point according to the following equation:  
These pins provide bias voltage to the upper MOSFET  
drivers. A single capacitor bootstrap circuit may be used to  
create a BOOT voltage suitable to drive a standard N-  
Channel MOSFET.  
I
R  
OCSET  
OCS  
I
= -------------------------------------------  
PEAK  
r
DS(ON)  
An overcurrent trip cycles the soft-start function.  
UGATE1 and UGATE2  
Pulling the OCSET/SD pin to ground resets the ISL6530 and  
all external MOSFETS are turned off allowing the two output  
voltage power rails to float.  
Connect UGATE1 and UGATE2 to the corresponding upper  
MOSFET gate. These pins provide the gate drive for the  
upper MOSFETs. UGATE2 is also monitored by the adaptive  
shoot through protection to determine when the upper FET  
PGOOD  
of the V regulator has turned off.  
TT  
A high level on this open-drain output indicates that both the  
V
and V regulators are within normal operating  
DDQ  
TT  
LGATE1 and LGATE2  
voltage ranges.  
Connect LGATE1 and LGATE2 to the corresponding lower  
MOSFET gate. These pins provide the gate drive for the  
lower MOSFETs. These pins are monitored by the adaptive  
shoot through protection to determine when the lower FET  
has turned off.  
GNDA  
Signal ground for the IC. Tie this pin to the ground plane  
through the lowest impedence connection available.  
VCC  
PGND1 and PGND2  
The 5V bias supply for the chip is connected to this pin. This  
pin is also the positive supply for the lower gate driver,  
LGATE2. Connect a well decoupled 5V supply to this pin.  
These are the power ground connections for the gate drivers  
of the PWM controllers. Tie these pins to the ground plane  
through the lowest impedence connection available.  
V2_SD  
OCSET/SD  
A high level on the V2_SD input places the V2 controller into  
“sleep” mode. In sleep mode, both UGATE2 and LGATE2  
are driven low, effectively floating the V supply.  
TT  
A resistor (R  
) connected from this pin to the drain of  
the upper MOSFET of the V regulator sets the  
OCSET  
DDQ  
, an internal 40µA current  
overcurrent trip point. R  
OCSET  
source (I  
), and the upper MOSFET on-resistance  
OCS  
FN9052.2  
6
November 15, 2004  
ISL6530  
While the V supply “floats”, it is held to about 50% of  
TT  
300kHz clocks. The clocks are phase locked and displaced  
90 to minimize noise coupling between the controllers.  
o
V
via a low current window regulator which drives V  
DDQ  
TT  
via the SENSE2 pin. The window regulator can overcome up  
The first regulator includes a precision 0.8V reference and is  
to at least ±10mA of leakage on V  
.
TT  
intended to provide the proper V  
to a DDRAM memory  
controller implements overcurrent  
DDQ  
While V2_SD is high, PGOOD is low.  
system. The V  
DDQ  
protection utilizing the r  
Following a fault condition, the V  
via a digital softstart circuit.  
of the upper MOSFET.  
DS(ON)  
PHASE1 and PHASE2  
regulator is softstarted  
DDQ  
Connect PHASE1 and PHASE2 to the corresponding upper  
MOSFET source. This pin is used as part of the upper  
MOSFET bootstrapped drives. PHASE1 is used to monitor  
the voltage drop across the upper MOSFET of the V  
regulator for over-current protection. The PHASE1 pin is  
Included in the ISL6530 is a precision V  
reference  
REF  
is a buffered representation of .5xV  
output. V  
. V  
REF  
DDQ REF  
DDQ  
is derived via a precision internal resistor divider connected  
to the SENSE1 terminal.  
monitored by the adaptive shoot through protection circuitry  
to determine when the upper FET of the V  
turned off.  
supply has  
DDQ  
The second PWM regulator is designed to provide V  
TT  
termination for the DDRAM signal lines. The reference to the  
V
regulator is V . Thus the V regulator provides a  
REF TT  
TT  
termination voltage equal to .5xV  
FB1, COMP1, FB2, and COMP2  
. The drain of the upper  
DDQ  
COMP1, COMP2, FB1, and FB2 are the available external  
pins of the error amplifiers. The FB1 and FB2 pins are the  
inverting inputs of each error amplifier and the COMP1 and  
COMP2 pins are the associated outputs. An appropriate AC  
network across these pins is used to compensate the  
voltage-controlled feedback loop of each converter.  
MOSFET of the V supply is connected to the regulated  
TT  
V
voltage. The V controller is designed to enable both  
TT  
DDQ  
sinking and sourcing current on the V rail.  
TT  
Two benefits result from the ISL6530 dual controller  
topology. First, as VREF is always .5xV  
, the V supply  
DDQ  
TT  
will track the V  
DDQ  
the overcurrent protection incorporated into the V  
will simultaneously protect the V supply.  
TT  
supply during softstart cycles. Second,  
supply  
VREF and VREF_IN  
DDQ  
VREF produces a voltage equal to one half of the voltage on  
SENSE1. This low current output is connected to the VREF  
input of the DDRAM devices being powered. This same  
Initialization  
voltage is used as the reference input of the V error  
The ISL6530 automatically initializes upon application of  
input power. Special sequencing of the input supplies is not  
necessary. The Power-On Reset (POR) function continually  
monitors the input bias supply voltage at the VCC pin. The  
POR function initiates soft-start operation after the 5V bias  
supply voltage exceeds its POR threshold.  
TT  
amplifier. Thus V is controlled to 50% of V  
TT  
.
DDQ  
VREF_IN is used as an option to overdrive the internal  
resistor divider network that sets the voltage for both  
VREF_OUT and the reference voltage for the V supply. A  
TT  
100pF capacitor between VREF_IN and ground is  
recommended for proper operation.  
Soft-Start  
The POR function initiates the digital soft start sequence. The  
PWM error amplifier reference input for the VDDQ regulator is  
clamped to a level proportional to the soft-start voltage. As the  
soft-start voltage slews up, the PWM comparator generates  
PHASE pulses of increasing width that charge the output  
capacitor(s). This method provides a rapid and controlled  
output voltage rise. The soft start sequence typically takes  
about 7ms.  
PVCC1  
This is the positive supply for the lower gate driver, LGATE1.  
PVCC1 is connected to a well decoupled 5V.  
SENSE1 and SENSE2  
Both SENSE1 and SENSE2 are connected directly to the  
regulated outputs of the V  
respectively. SENSE1 is used as an input to create the  
voltage at VREF_OUT and the reference voltage for the V  
supply. SENSE2 is used as the regulation point for the  
window regulator that is enabled in V2_SD mode.  
and V supplies,  
DDQ  
TT  
1
2
TT  
--  
With the V regulator reference held at  
TT  
it will  
V  
DDQ  
automatically track the ramp of the V  
softstart, thus  
DDQ  
enabling a soft-start for V  
.
TT  
Figure 2 shows the soft-start sequence for a typical application.  
At t0, the +5V VCC bias voltage starts to ramp. Once the  
voltage on VCC crosses the POR threshold at time t1, both  
outputs begin their soft-start sequence. The triangle waveforms  
from the PWM oscillators are compared to the rising error  
amplifier output voltage. As the error amplifier voltage  
increases, the pulse-widths on the UGATE pins increase to  
reach their steady-state duty cycle at time t2.  
Functional Description  
Overview  
The ISL6530 contains control and drive circuitry for two  
synchronous buck PWM voltage regulators. Both regulators  
utilize 5V bootstrapped output topology to allow use of low  
cost N-channel MOSFETs. The regulators are driven by  
FN9052.2  
7
November 15, 2004  
ISL6530  
When the V2_SD input of the ISL6530 is driven high, the  
regulator is placed into a “sleep” state. In the sleep  
V
TT  
state the main V regulator is disabled, with both the  
TT  
VCC (5V)  
upper and lower MOSFETs being turned off. The V bus  
TT  
(1V/DIV)  
is maintained at close to .5xVdd via a low current window  
regulator which drives V via the SENSE2 pin.  
TT  
Maintaining V at .5xV  
TT  
consumes negligible power  
DDQ  
and enables rapid wake-up from sleep mode without the  
V
(2.5V)  
DDQ  
need of softstarting the V regulator. During this power  
TT  
down mode, PGOOD is held LOW.  
V
(1.25V)  
TT  
Output Voltage Selection  
0V  
The output voltage of the V  
regulator can be  
DDQ  
programmed to any level between V (i.e. +5V) and the  
T2  
T0  
T1  
IN  
TIME  
internal reference, 0.8V. An external resistor divider is used  
to scale the output voltage relative to the reference voltage  
and feed it back to the inverting input of the error amplifier,  
see Figure 3. However, since the value of R1 affects the  
values of the rest of the compensation components, it is  
advisable to keep its value less than 5k. R4 can be  
calculated based on the following equation:  
FIGURE 2. SOFT-START INTERVAL  
Shoot-Through Protection  
A shoot-through condition occurs when both the upper  
MOSFET and lower MOSFET are turned on simultaneously,  
effectively shorting the input voltage to ground. To protect  
the regulators from a shoot-through condition, the ISL6530  
incorporates specialized circuitry which insures that  
complementary MOSFETs are not ON simultaneously.  
R1 × 0.8V  
R4 = -------------------------------------  
V
0.8V  
OUT1  
If the output voltage desired is 0.8V, simply route VOUT1  
back to the FB pin through R1, but do not populate R4.  
The adaptive shoot-through protection utilized by the V  
DDQ  
regulator looks at the lower gate drive pin, LGATE1, and the  
phase node, PHASE1, to determine whether a MOSFET is  
ON or OFF. If PHASE1 is below 0.8V, the upper gate is  
defined as being OFF. Similarly, if LGATE1 is below 0.8V, the  
lower MOSFET is defined as being OFF. This method of  
+5V  
D1  
VCC  
BOOT1  
shoot-through protection allows the V  
source current only.  
regulator to  
DDQ  
Due to the necessity of sinking current, the V regulator  
TT  
employs a modified protection scheme from that of the  
C4  
Q1  
UGATE1  
L
OUT  
V
V
regulator. If the voltage from UGATE2 or from  
DDQ  
DDQ  
PHASE1  
LGATE1  
ISL6530  
LGATE2 to GND is less than 0.8V, then the respective  
MOSFET is defined as being OFF and the other MOSFET is  
turned ON.  
Q2  
+
C
OUT1  
FB1  
Since the voltage of the lower MOSFET gates and the upper  
C1  
R1  
C3  
MOSFET gate of the V supply are being measured to  
COMP1  
TT  
R3  
determine the state of the MOSFET, the designer is  
encouraged to consider the repercussions of introducing  
external components between the gate drivers and their  
respective MOSFET gates before actually implementing  
such measures. Doing so may interfere with the shoot-  
through protection.  
C2  
R2  
R4  
FIGURE 3. OUTPUT VOLTAGE SELECTION OF V  
DDQ  
Power Down Mode  
V
Reference Overdrive  
TT  
DDRAM systems include a sleep state in which the V  
DDQ  
The ISL6530 allows the designer to bypass the internal 50%  
tracking of V that is used as the reference for V . The  
voltage to the memories is maintained, but signaling is  
suspended. During this mode the V termination voltage is  
DDQ TT  
TT  
ISL6530 was designed to divide down the V voltage by  
no longer needed. The only load placed on the V bus is  
TT  
the leakage of the associated signal pins of the DDRAM and  
DDQ  
50% through two internal matched resistances. These  
resistances are typically 200k.  
memory controller ICs.  
FN9052.2  
November 15, 2004  
8
ISL6530  
One method that may be employed to bypass the internal  
reference generation is to supply an external reference  
programs the overcurrent trip level (see Figure 1). An internal  
V
40µA (typical) current sink develops a voltage across R  
TT  
OCSET  
that is referenced to V . When the voltage across the upper  
directly to the V  
pin. When doing this the SENSE1 pin  
REF_IN  
must remain unconnected. Caution must be exercised when  
IN  
MOSFET of V  
voltage across R  
(also referenced to V ) exceeds the  
DDQ  
IN  
, the overcurrent function initiates a  
using this method as the V regulator does not employ a  
TT  
OCSET  
soft-start of its own.  
soft-start sequence.  
Figure 5 illustrates the protection feature responding to an  
over current event on V . At time T0, an over current  
A second method would be to overdrive the internal  
resistors. Figure 4 shows how to implement this method. The  
external resistors used to overdrive the internal resistors  
should be less than 2kand have a tolerance of 1% or  
better. This method still supplies a buffer between the  
DDQ  
condition is sensed across the upper MOSFET of the V  
DDQ  
regulator. As a result, both regulators are quickly shutdown  
and the internal soft-start function begins producing soft-  
start ramps. The delay interval seen by the output is  
equivalent to three soft-start cycles. The fourth internal soft-  
start cycle initiates a normal soft-start ramp of the output, at  
time T1. Both outputs are brought back into regulation by  
time t2, as long as the overcurrent event has cleared.  
resistor network and any loading on the V  
pin. If there is  
REF  
pin, then no buffering is necessary  
no loading on the V  
REF  
and the reference voltage created by the resistor network  
can be tied directly to V  
.
REF  
V
DDQ  
ISL6530  
Had the cause of the overcurrent still been present after the  
delay interval, the overcurrent condition would be sensed  
and both regulators would be shut down again for another  
delay interval of three soft-start cycles. The resulting hiccup  
mode style of protection would continue to repeat  
indefinitely.  
SENSE1  
VREF_IN  
R
R
A
VREF  
+
-
B
V
(2.5V)  
DDQ  
TO ERROR  
AMPLIFIER  
V
(1.25V)  
TT  
FIGURE 4. V REFERENCE OVERDRIVE  
TT  
Converter Shutdown  
Pulling and holding the OCSET/SD pin below 0.8V will  
shutdown both regulators. During this state, PGOOD will be  
held LOW. Upon release of the OCSET/SD pin, the IC enters  
into a soft start cycle which brings both outputs back into  
regulation.  
0V  
INTERNAL SOFT-START FUNCTION  
DELAY INTERVAL  
Voltage Monitoring  
The ISL6530 offers a PGOOD signal that will communicate  
whether the regulation of both V  
and V are within  
DDQ  
TT  
±15% of regulation, the V2_SD pin is held low and the bias  
voltage of the IC is above the POR level. If all the criteria  
above are true, the PGOOD pin will be at a high impedence  
level. When one or more of the criteria listed above are false,  
the PGOOD pin will be held low.  
T0  
T1  
T2  
TIME  
FIGURE 5. OVERCURRENT PROTECTION RESPONSE  
Overcurrent Protection  
The overcurrent function will trip at a peak inductor current  
The overcurrent function protects the converter from a shorted  
(I  
determined by:  
PEAK)  
output by using the upper MOSFET on-resistance, r  
, of  
DS(ON)  
V
to monitor the current. This method enhances the  
I
x R  
OCSET OCSET  
DDQ  
I
= ----------------------------------------------------  
PEAK  
converter’s efficiency and reduces cost by eliminating a  
current sensing resistor.  
r
DS(ON)  
where I  
OCSET  
is the internal OCSET current source (40µA  
The over-current function cycles the soft-start function in a  
typical). The OC trip point varies mainly due to the MOSFET  
hiccup mode to provide fault protection. A resistor (R  
)
OCSET  
FN9052.2  
9
November 15, 2004  
ISL6530  
r
variations. To avoid over-current tripping in the  
DS(ON)  
+5V  
normal operating load range, find the R  
the equation above with:  
resistor from  
OCSET  
ISL6530  
1. The maximum r  
2. The minimum I  
at the highest junction temperature.  
DS(ON)  
UGATE1  
PHASE1  
V
DDQ  
from the specification table.  
OCSET  
LGATE1  
(∆I)  
2
I
> I  
+ ----------  
,
OUT(MAX)  
3. Determine I  
PEAK  
for  
PEAK  
DDR  
SDRAM  
where I is the output inductor ripple current.  
UGATE2  
PHASE2  
+
-
For an equation for the ripple current see the section under  
component guidelines titled Output Inductor Selection.  
V
TT  
R
T
LGATE2  
V
REF  
A small ceramic capacitor should be placed in parallel with  
R
to smooth the voltage across  
R
in the  
OCSET  
OCSET  
presence of switching noise on the input voltage.  
FIGURE 6. V CURRENT SINKING LOOP  
TT  
Current Sinking  
Application Guidelines  
The ISL6530 V regulator incorporates a MOSFET shoot-  
TT  
Layout Considerations  
through protection method which allows the converter to sink  
current as well as source current. Care should be exercised  
when designing a converter with the ISL6530 when it is  
known that the converter may sink current.  
Layout is very important in high frequency switching  
converter design. With power devices switching efficiently at  
300kHz, the resulting current transitions from one device to  
another cause 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 the voltage  
spikes in the converters.  
When the converter is sinking current, it is behaving as a  
boost converter that is regulating its input voltage. This  
means that the converter is boosting current into the input  
rail of the regulator. If there is nowhere for this current to go,  
such as to other distributed loads on the rail or through a  
voltage limiting protection device, the capacitance on this rail  
will absorb the current. This situation will allow the voltage  
level of the input rail to increase. If the voltage level of the rail  
is boosted to a level that exceeds the maximum voltage  
rating of any components attached to the input rail, then  
those components may experience an irreversible failure or  
experience stress that may shorten their lifespan. Ensuring  
that there is a path for the current to flow other than the  
capacitance on the rail will prevent this failure mode.  
As an example, consider the turn-off transition of the PWM  
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 lower 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 minimizes the magnitude of voltage  
spikes.  
To insure that the current does not boost up the input rail  
There are two sets of critical components in a DC-DC  
converter using the ISL6530. The switching components are  
the most critical because they switch large amounts of  
energy, and therefore tend to generate large amounts of  
noise. Next are the small signal components which connect  
to sensitive nodes or supply critical bypass current and  
signal coupling.  
voltage of the V regulator, it is recommended that the  
TT  
input rail of the V regulator be the output of the V  
TT  
DDQ  
regulator. The current being sunk by the V regulator will  
TT  
be fed into the V  
DDQ  
rail and then drawn into the DDR  
SDRAM memory module and back into the V regulator.  
TT  
Figure 6 shows the recommended configuration and the  
resulting current loop.  
A multi-layer printed circuit board is recommended. Figure 7  
shows the connections of the critical components in the  
converter. Note that capacitors C and C  
could each  
IN OUT  
represent numerous physical capacitors. Dedicate one solid  
layer, usually a middle layer of the PC board, for a ground  
plane and make all critical component ground connections  
with vias to this layer. Dedicate another solid layer as a  
power plane and break this plane into smaller islands of  
common voltage levels. Keep the metal runs from the  
PHASE terminals to the output inductor short. The power  
plane should support the input power and output power  
FN9052.2  
10  
November 15, 2004  
ISL6530  
nodes. Use copper filled polygons on the top and bottom  
The switching components should be placed close to the  
ISL6530 first. Minimize the length of the connections  
circuit layers for the phase nodes. Use the remaining printed  
circuit layers for small signal wiring. The wiring traces from  
the GATE pins to the MOSFET gates should be kept short  
and wide enough to easily handle the 1A of drive current.  
between the input capacitors, C , and the power switches  
IN  
by placing them nearby. Position both the ceramic and bulk  
input capacitors as close to the upper MOSFET drain as  
possible. Position the output inductor and output capacitors  
between the upper MOSFET and lower diode and the load.  
+5V V  
IN  
ISL6530  
VCC  
The critical small signal components include any bypass  
capacitors, feedback components, and compensation  
C
BP  
C
D1  
IN  
GND  
components. Position the bypass capacitor, C , close to the  
BP  
VCC pin with a via directly to the ground plane. Place the  
PWM converter compensation components close to the FB  
and COMP pins. The feedback resistors for both regulators  
should also be located as close as possible to the relevant  
FB pin with vias tied straight to the ground plane as required.  
BOOT1  
C
BOOT1  
Q1  
Q2  
UGATE1  
PHASE1  
L
OUT1  
V
PHASE1  
DDQ  
Feedback Compensation  
Figure 8 highlights the voltage-mode control loop for a  
synchronous-rectified buck converter. The output voltage  
C
LGATE1  
PGND1  
COMP1  
OUT1  
(V  
) is regulated to the Reference voltage level. The  
OUT  
error amplifier (Error Amp) output (V ) is compared with  
E/A  
C
2A  
the oscillator (OSC) triangular wave to provide a pulse-  
C
1A  
R
2A  
R
width modulated (PWM) wave with an amplitude of V at  
1A  
IN  
FB1  
the PHASE node. The PWM wave is smoothed by the output  
C
R
3A  
3A  
R4  
filter (L and C ).  
O
O
SENSE1  
The modulator transfer function is the small-signal transfer  
function of V /V . This function is dominated by a DC  
+5V V  
OUT E/A  
Gain and the output filter (L and C ), with a double pole  
IN  
D2  
O
O
V
DDQ  
Q3  
break frequency at F and a zero at F  
. The DC Gain of  
LC ESR  
BOOT2  
the modulator is simply the input voltage (V ) divided by the  
IN  
C
BOOT2  
peak-to-peak oscillator voltage V  
OSC  
UGATE2  
PHASE2  
L
OUT2  
Modulator Break Frequency Equations  
V
PHASE2  
TT  
1
1
F
= -----------------------------------------  
F
= ------------------------------------------  
LC  
ESR  
2π x ESR x C  
Q4  
2π x  
L
x C  
O O  
O
C
LGATE2  
PGND2  
OUT2  
The compensation network consists of the error amplifier  
(internal to the ISL6530) and the impedance networks Z  
IN  
COMP1  
C
and Z . The goal of the compensation network is to provide  
2B  
FB  
C
1B  
a closed loop transfer function with the highest 0dB crossing  
R
2B  
R
1B  
frequency (f  
) and adequate phase margin. Phase margin  
is the difference between the closed loop phase at f and  
FB1  
0dB  
C
R
3B  
3B  
0dB  
180 degrees. The equations below relate the compensation  
network’s poles, zeros and gain to the components (R , R ,  
SENSE2  
1
2
R , C , C , and C ) in Figure 7. Use these guidelines for  
3
1
2
3
locating the poles and zeros of the compensation network:  
KEY  
ISLAND ON POWER PLANE LAYER  
ISLAND ON CIRCUIT PLANE LAYER  
1. Pick gain (R /R ) for desired converter bandwidth.  
2
1
2. Place first zero below filter’s double pole (~75% F ).  
LC  
VIA CONNECTION TO GROUND PLANE  
3. Place second zero at filter’s double pole.  
4. Place first pole at the ESR zero.  
FIGURE 7. PRINTED CIRCUIT BOARD POWER PLANES  
AND ISLANDS  
5. Place second pole at half the switching frequency.  
6. Check gain against error amplifier’s open-loop gain.  
7. Estimate phase margin - repeat if necessary.  
FN9052.2  
November 15, 2004  
11  
ISL6530  
.
V
IN  
DRIVER  
DRIVER  
OPEN LOOP  
ERROR AMP GAIN  
F
F
F
P1  
F
OSC  
Z1  
Z2  
P2  
PWM  
100  
80  
L
O
COMPARATOR  
V
OUT  
V
IN  
---------------  
20log  
-
PHASE  
V
+
DV  
OSC  
C
O
OSC  
60  
ESR  
(PARASITIC)  
40  
COMPENSATION  
GAIN  
Z
FB  
20  
V
E/A  
Z
-
IN  
0
+
R2  
-------  
20log  
R1  
REFERENCE  
ERROR  
AMP  
-20  
-40  
-60  
MODULATOR  
GAIN  
LOOP GAIN  
10M  
F
F
ESR  
LC  
DETAILED COMPENSATION COMPONENTS  
Z
FB  
10  
100  
1K  
10K  
100K  
1M  
V
OUT  
C
1
Z
FREQUENCY (Hz)  
IN  
C
C
R
R
3
2
3
2
FIGURE 9. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN  
R
1
COMP  
Component Selection Guidelines  
FB  
Output Capacitor Selection  
-
+
An output capacitor is required to filter the output and supply  
the load transient current. The filtering requirements are a  
function of the switching frequency and the ripple current.  
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  
capacitors and careful layout.  
ISL6530  
REFERENCE  
FIGURE 8. VOLTAGE-MODE BUCK CONVERTER  
COMPENSATION DESIGN  
Compensation Break Frequency Equations  
Modern digital ICs can produce high transient load slew  
rates. High-frequency 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 ESR (effective series resistance) and voltage rating  
requirements rather than actual capacitance requirements.  
1
1
F
= ----------------------------------  
F
F
= --------------------------------------------------------  
Z1  
Z2  
P1  
P2  
2π × R × C  
C
x C  
2
2
1
2
---------------------  
2π x R  
x
2
C
+ C  
2
1
1
1
F
= ------------------------------------------------------  
2π x (R + R ) x C  
= -----------------------------------  
2π x R x C  
3
1
3
3
3
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.  
Figure 9 shows an asymptotic plot of the DC-DC converter’s  
gain vs frequency. The actual modulator gain has a high gain  
peak due to the high Q factor of the output filter and is not  
shown in Figure 9. Using the above guidelines should give a  
compensation gain similar to the curve plotted. The open loop  
error amplifier gain bounds the compensation gain. Check the  
Use only specialized low-ESR capacitors intended for  
switching-regulator applications for the bulk capacitors. The  
bulk capacitor’s ESR will determine the output ripple voltage  
and the initial voltage drop after a high slew-rate transient. An  
aluminum electrolytic capacitor’s ESR value is related to the  
case size with lower ESR available in larger case sizes.  
However, the equivalent series inductance (ESL) of these  
capacitors increases with case size and can reduce the  
usefulness of the capacitor to high slew-rate transient loading.  
Unfortunately, ESL is not a specified parameter. Work with  
your capacitor supplier and measure the capacitor’s  
compensation gain at F with the capabilities of the error  
P2  
amplifier. The closed loop gain is constructed on the graph of  
Figure 9 by adding the modulator gain (in dB) to the  
compensation gain (in dB). This is equivalent to multiplying  
the modulator transfer function to the compensation transfer  
function and plotting the gain.  
The compensation gain uses external impedance networks  
Z
and Z to provide a stable, high bandwidth (BW) overall  
FB  
IN  
loop. A stable control loop has a gain crossing with  
-20dB/decade slope and a phase margin greater than 45  
degrees. Include worst case component variations when  
determining phase margin.  
impedance with frequency to select a suitable component. In  
most cases, multiple electrolytic capacitors of small case size  
perform better than a single large case capacitor.  
FN9052.2  
12  
November 15, 2004  
ISL6530  
conservative guideline. The RMS current rating requirement  
Output Inductor Selection  
for the input capacitor of a buck regulator is approximately  
1/2 the DC load current.  
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 the following equations:  
The maximum RMS current required by the regulator may be  
closely approximated through the following equation:  
2
   
VOUT  
-------------  
VIN  
V
IN VOUT VOUT  
2
1
   
------ ---------------------------- -------------  
IRMS  
=
× IOUT  
+
×
×
12  
L × fs  
VIN  
MAX  
MAX  
V
- V  
IN OUT  
V
OUT  
V  
OUT  
= I x ESR  
I =  
x
f x L  
V
IN  
s
For a through-hole design, several electrolytic capacitors may  
be needed. For surface mount designs, solid tantalum  
capacitors can be used, but caution must be exercised with  
regard to the capacitor surge currentrating. These capacitors  
must be capable of handling the surge-current at power-up.  
Some capacitor series available from reputable manufacturers  
are surge current tested.  
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.  
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  
ISL6530 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.  
MOSFET Selection/Considerations  
The ISL6530 requires two N-Channel power MOSFETs for  
each PWM regulator. These should be selected based upon  
r
, gate supply requirements, and thermal management  
DS(ON)  
requirements.  
In high-current applications, the MOSFET power dissipation,  
package selection and heatsink are the dominant design  
factors. The power dissipation includes two loss components;  
conduction loss and switching loss. The conduction losses are  
the largest component of power dissipation for both the upper  
and the lower MOSFETs. These losses are distributed between  
the two MOSFETs according to duty factor. The switching  
losses seen when sourcing current will be different from the  
The response time to a transient is different for the  
application of load and the removal of load. The following  
equations give the approximate response time interval for  
application and removal of a transient load:  
L x I  
L x I  
TRAN  
TRAN  
- V  
t
=
t
=
FALL  
RISE  
switching losses seen when sinking current. The V  
DDQ  
V
V
OUT  
IN OUT  
regulator will only source current while the V regulator can  
TT  
sink and source. When sourcing current, the upper MOSFET  
realizes most of the switching losses. The lower switch realizes  
most of the switching losses when the converter is sinking  
current (see the equations below). These equations assume  
linear voltage-current transitions and do not adequately model  
power loss due the reverse-recovery of the upper and lower  
MOSFET’s body diode. The gate-charge losses are dissipated  
by the ISL6530 and don't heat the MOSFETs. However, large  
where: I  
is the transient load current step, t  
is the  
TRAN  
RISE  
is the  
response time to the application of load, and t  
FALL  
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.  
Input Capacitor Selection  
gate-charge increases the switching interval, t which  
SW  
increases the MOSFET switching losses.  
LOSSES WHILE SOURCING CURRENT  
Use a mix of input bypass capacitors to control the voltage  
overshoot across the MOSFETs. Use small ceramic  
capacitors for high frequency decoupling and bulk capacitors  
2
1
--  
× D + Io × V × t  
P
= Io × r  
× f  
to supply the current needed each time Q turns on. Place the  
UPPER  
DS(ON)  
IN SW s  
1
2
2
small ceramic capacitors physically close to the MOSFETs  
P
= Io x r  
x (1 - D)  
LOWER  
DS(ON)  
and between the drain of Q and the source of Q .  
1
2
LOSSES WHILE SINKING CURRENT  
2
The important parameters for the bulk input capacitor are the  
voltage rating and the RMS current rating. For reliable  
operation, select the bulk capacitor 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 1.25 times greater than the maximum  
input voltage and a voltage rating of 1.5 times is a  
P
= Io x r  
2
x D  
DS(ON)  
UPPER  
1
2
--  
× (1 D) + Io × V × t  
P
= Io × r  
× f  
s
LOWER  
DS(ON)  
IN SW  
Where: D is the duty cycle = V ,  
/ V  
is the combined switch ON and OFF time, and  
OUT IN  
t
SW  
f is the switching frequency.  
s
FN9052.2  
13  
November 15, 2004  
ISL6530  
Ensure that both MOSFETs are within their maximum junction  
temperature at high ambient temperature by calculating the  
temperature rise according to package thermal-resistance  
specifications. A separate heatsink may be necessary  
depending upon MOSFET power, package type, ambient  
temperature and air flow.  
The bootstrap capacitor begins its refresh cycle when the  
gate drive begins to turn-off the upper MOSFET. A refresh  
cycle ends when the upper MOSFET is turned on again,  
which varies depending on the switching frequency and  
duty cycle.  
The minimum bootstrap capacitance can be calculated by  
Given the reduced available gate bias voltage (5V), logic-  
level or sub-logic-level transistors should be used for both N-  
MOSFETs. Caution should be exercised when using devices  
rearranging the previous equation and solving for C  
.
BOOT  
Q
GATE  
----------------------------------------------------  
C
BOOT  
V
V  
BOOT1  
BOOT2  
with very low gate thresholds (V ). The shoot-through  
TH  
protection circuitry may be circumvented by these  
Typical gate charge values for MOSFETs considered in  
these types of applications range from 20 to 100nC. Since  
the voltage drop across Q is negligible, V is  
MOSFETs. Very high dv/dt transitions on the phase node  
may cause the Miller capacitance to couple the lower gate  
with the phase node and cause an undesireable turn on of  
the lower MOSFET while the upper MOSFET is on.  
LOWER BOOT1  
simply VCC - V . A Schottky diode is recommended to  
D
minimize the voltage drop across the bootstrap capacitor  
during the on-time of the upper MOSFET. Initial calculations  
Bootstrap Component Selection  
with V  
no less than 4V will quickly help narrow the  
External bootstrap components, a diode and capacitor, are  
required to provide sufficient gate enhancement to the upper  
MOSFET. The internal MOSFET gate driver is supplied by  
the external bootstrap circuitry as shown in Figure 10. The  
BOOT2  
bootstrap capacitor range.  
For example, consider an upper MOSFET is chosen with a  
maximum gate charge, Q , of 100nC. Limiting the voltage  
drop across the bootstrap capacitor to 1V results in a value  
of no less than 0.1µF. The tolerance of the ceramic capacitor  
should also be considered when selecting the final bootstrap  
capacitance value.  
g
boot capacitor, C  
, develops a floating supply voltage  
BOOT  
referenced to the PHASE pin. This supply is refreshed each  
cycle, when D conducts, to a voltage of VCC less the  
BOOT  
boot diode drop, V , plus the voltage rise across Q  
D
.
LOWER  
VCC  
A fast recovery diode is recommended when selecting a  
bootstrap diode to reduce the impact of reverse recovery  
D
BOOT  
+
V
-
V
IN  
D
charge loss. Otherwise, the recovery charge, Q , would  
RR  
have to be added to the gate charge of the MOSFET and  
taken into consideration when calculating the minimum  
bootstrap capacitance.  
BOOTn  
C
ISL6530  
BOOT  
UGATEn  
PHASEn  
Q
Q
UPPER  
NOTE:  
ª V  
V
-V  
D
G-S  
CC  
LGATEn  
LOWER  
-
+
NOTE:  
ª V  
V
G-S  
CC  
GND  
FIGURE 10. UPPER GATE DRIVE BOOTSTRAP  
Just after the PWM switching cycle begins and the charge  
transfer from the bootstrap capacitor to the gate capacitance  
is complete, the voltage on the bootstrap capacitor is at its  
lowest point during the switching cycle. The charge lost on  
the bootstrap capacitor will be equal to the charge  
transferred to the equivalent gate-source capacitance of the  
upper MOSFET as shown:  
Q
= C  
× (V  
V  
)
BOOT2  
GATE  
BOOT  
BOOT1  
where Q  
is the maximum total gate charge of the upper  
GATE  
MOSFET, C  
BOOT  
is the bootstrap capacitance, V  
is  
BOOT1  
the bootstrap voltage immediately before turn-on, and  
V
is the bootstrap voltage immediately after turn-on.  
BOOT2  
FN9052.2  
November 15, 2004  
14  
ISL6530  
ISL6530 DC-DC Converter Application Circuit  
Figure 11 shows an application circuit for a DDR SDRAM  
of-Materials and circuit board description, can be found in  
power supply, including V (+2.5V) and V (+1.25V).  
Application Note AN9993.  
DDQ TT  
Detailed information on the circuit, including a complete Bill-  
+5V  
C
0.1µF  
R
C
2
1
1
3.48kΩ  
1000pF  
D
1
C
C
3
4,5  
150µF(x2)  
OCSET/SD  
VCC  
1.0µF  
BOOT1  
V2_SD  
Q
1
PGOOD  
VREF  
UGATE1  
PHASE1  
C
0.1µF  
6
V
DDQ  
@10A  
L
1µH  
1
VREF_IN  
GNDA  
C
PVCC1  
7,8,9,10  
150µF(x4)  
Q
C
2
30  
100pF  
LGATE1  
C
15  
0.1µF  
PGND1  
ISL6530  
D
2
C
26  
5600pF  
COMP1  
BOOT2  
C
17  
1.0µF  
C
R
27  
100pF  
26  
UGATE2  
6.34kΩ  
C
16  
0.1µF  
V
TT  
@5A  
L
1µH  
FB1  
PHASE2  
LGATE2  
2
R
19  
3.01kΩ  
C
R
18,19  
150µF(x2)  
20  
1.43kΩ  
Q
3
C
25  
15000pF  
PGND2  
SENSE1  
COMP2  
FB2  
SENSE2  
R
25  
100Ω  
C
68pF  
R
24  
21  
3.01kΩ  
R
R
23  
8.87kΩ  
22  
158Ω  
C
C
10000pF  
2700pF  
22  
23  
Component Selection Notes:  
C4,5,7,8,9,10,18,19 - Each 150mF, Panasonic EEF-UE0J151R  
D1,2 - Each 30mA Schottky Diode, MA732  
Q1,2 - Each Fairchild MOSFET; ITF86130DK8  
Q3 - Fairchild MOSFET; ITF86110DK8  
L1,2 - Each 1mH Inductor, Panasonic P/N ETQ-P6F1ROSFA  
FIGURE 11. DDR SDRAM VOLTAGE REGULATOR  
FN9052.2  
November 15, 2004  
15  
Small Outline Plastic Packages (SOIC)  
N
M24.3 (JEDEC MS-013-AD ISSUE C)  
INDEX  
AREA  
0.25(0.010)  
M
B M  
H
24 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE  
E
INCHES  
MILLIMETERS  
-B-  
SYMBOL  
MIN  
MAX  
MIN  
2.35  
0.10  
0.33  
0.23  
MAX  
2.65  
0.30  
0.51  
0.32  
15.60  
7.60  
NOTES  
A
A1  
B
C
D
E
e
0.0926  
0.0040  
0.013  
0.1043  
0.0118  
0.020  
-
1
2
3
L
-
9
SEATING PLANE  
A
0.0091  
0.5985  
0.2914  
0.0125  
-
-A-  
o
h x 45  
D
0.6141 15.20  
3
0.2992  
7.40  
4
-C-  
α
µ
0.05 BSC  
1.27 BSC  
-
e
A1  
H
h
0.394  
0.010  
0.016  
0.419  
0.029  
0.050  
10.00  
0.25  
0.40  
10.65  
0.75  
1.27  
-
C
B
0.10(0.004)  
5
0.25(0.010) M  
C A M B S  
L
6
N
α
24  
24  
7
NOTES:  
o
o
o
o
0
8
0
8
-
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of  
Publication Number 95.  
Rev. 0 12/93  
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.  
3. Dimension “D” does not include mold flash, protrusions or gate burrs.  
Mold flash, protrusion and gate burrs shall not exceed 0.15mm  
(0.006 inch) per side.  
4. Dimension “E” does not include interlead flash or protrusions. Inter-  
lead flash and protrusions shall not exceed 0.25mm (0.010 inch) per  
side.  
5. The chamfer on the body is optional. If it is not present, a visual index  
feature must be located within the crosshatched area.  
6. “L” is the length of terminal for soldering to a substrate.  
7. “N” is the number of terminal positions.  
8. Terminal numbers are shown for reference only.  
9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater  
above the seating plane, shall not exceed a maximum value of  
0.61mm (0.024 inch)  
10. Controlling dimension: MILLIMETER. Converted inch dimensions  
are not necessarily exact.  
FN9052.2  
16  
November 15, 2004  
ISL6530  
Quad Flat No-Lead Plastic Package (QFN)  
Micro Lead Frame Plastic Package (MLFP)  
L32.5x5  
32 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE  
(COMPLIANT TO JEDEC MO-220VHHD-2 ISSUE C  
MILLIMETERS  
SYMBOL  
MIN  
NOMINAL  
MAX  
1.00  
0.05  
1.00  
NOTES  
A
A1  
A2  
A3  
b
0.80  
0.90  
-
-
-
-
-
-
9
0.20 REF  
9
0.18  
2.95  
2.95  
0.23  
0.30  
3.25  
3.25  
5,8  
D
5.00 BSC  
-
D1  
D2  
E
4.75 BSC  
9
3.10  
7,8  
5.00 BSC  
-
E1  
E2  
e
4.75 BSC  
9
3.10  
7,8  
0.50 BSC  
-
k
0.25  
0.30  
-
-
-
-
L
0.40  
0.50  
0.15  
8
L1  
N
-
32  
8
8
-
10  
2
Nd  
Ne  
P
3
8
-
3
0.60  
12  
9
θ
-
-
9
Rev. 1 10/02  
NOTES:  
1. Dimensioning and tolerancing conform to ASME Y14.5-1994.  
2. N is the number of terminals.  
3. Nd and Ne refer to the number of terminals on each D and E.  
4. All dimensions are in millimeters. Angles are in degrees.  
5. Dimension b applies to the metallized terminal and is measured  
between 0.15mm and 0.30mm from the terminal tip.  
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.  
7. Dimensions D2 and E2 are for the exposed pads which provide  
improved electrical and thermal performance.  
8. Nominal dimensionsare provided toassistwith PCBLandPattern  
Design efforts, see Intersil Technical Brief TB389.  
9. Features and dimensions A2, A3, D1, E1, P & θ are present when  
Anvil singulation method is used and not present for saw  
singulation.  
10. Depending on the method of lead termination at the edge of the  
package, a maximum 0.15mm pull back (L1) maybe present. L  
minus L1 to be equal to or greater than 0.3mm.  
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.  
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality  
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without  
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and  
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result  
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.  
For information regarding Intersil Corporation and its products, see www.intersil.com  
FN9052.2  
17  
November 15, 2004  

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