ISL6532ACR-T [INTERSIL]

ACPI Regulator/Controller for Dual Channel DDR Memory Systems; ACPI稳压器/控制器双通道DDR内存系统
ISL6532ACR-T
型号: ISL6532ACR-T
厂家: Intersil    Intersil
描述:

ACPI Regulator/Controller for Dual Channel DDR Memory Systems
ACPI稳压器/控制器双通道DDR内存系统

稳压器 开关 双倍数据速率 控制器
文件: 总16页 (文件大小:495K)
中文:  中文翻译
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ISL6532A  
®
Data Sheet  
August 2004  
FN9099.3  
ACPI Regulator/Controller for  
Dual Channel DDR Memory Systems  
Features  
• Generates 3 Regulated Voltages  
The ISL6532A provides a complete ACPI compliant power  
solution for up to 4 DIMM dual channel DDR/DDR2 Memory  
systems. Included are both a synchronous buck controller  
- Synchronous Buck PWM Controller with Standby LDO  
- 3A Integrated Sink/Source Linear Regulator with  
Accurate VDDQ/2 Divider Reference.  
and integrated LDO to supply V  
with high current during  
DDQ  
- Glitch-free Transitions During State Changes  
- LDO Regulator for 1.5V Video and Core voltage  
S0/S1 states and standby current during S3 state. During  
S0/S1 state, a fully integrated sink-source regulator  
generates an accurate (V  
/2) high current V voltage  
• ACPI compliant sleep state control  
DDQ  
TT  
without the need for a negative supply. A buffered version of  
the V /2 reference is provided as V . An LDO  
controller is also integrated for AGP core voltage regulation.  
• Integrated V  
REF  
Buffer  
DDQ REF  
• PWM Controller Drives Low Cost N-Channel MOSFETs  
• 250kHz Constant Frequency Operation  
• Tight Output Voltage Regulation  
The switching PWM controller drives two N-Channel  
MOSFETs in a synchronous-rectified buck converter  
topology. The synchronous buck converter uses voltage-  
mode control with fast transient response. Both the switching  
regulator and standby LDO provide a maximum static  
regulation tolerance of ±2% over line, load, and temperature  
ranges. The output is user-adjustable by means of external  
resistors down to 0.8V.  
- All Outputs: ±2% Over Temperature  
• 5V or 3.3V Down Conversion  
• Fully-Adjustable Outputs with Wide Voltage Range: Down  
to 0.8V supports DDR and DDR2 Specifications  
• Simple Single-Loop Voltage-Mode PWM Control Design  
• Fast PWM Converter Transient Response  
• Under and Over-voltage Monitoring on All Outputs  
• OCP on the Switching Regulator  
Switching memory core output between the PWM regulator  
and the standby LDO during state transitions is  
accomplished smoothly via the internal ACPI control  
circuitry. The NCH signal provides synchronized switching of  
a backfeed blocking switch during the transitions eliminating  
the need to route 5V Dual to the memory supply.  
• Integrated Thermal Shutdown Protection  
• QFN Package Option  
- QFN Compliant to JEDEC PUB95 MO-220 QFN - Quad  
Flat No Leads - Product Outline  
An integrated soft-start feature brings all outputs into  
regulation in a controlled manner when returning to S0/S1  
state from any sleep state. During S0 the PGOOD signal  
- QFN Near Chip Scale Package Footprint; Improves  
PCB Efficiency, Thinner in Profile  
• Pb-free available  
indicates V is within spec and operational.  
TT  
Each output is monitored for under and over-voltage events.  
The switching regulator has over current protection. Thermal  
shutdown is integrated.  
Applications  
Single and Dual Channel DDR Memory Power Systems in  
ACPI compliant PCs  
Pinout  
ISL6532A (QFN) TOP VIEW  
Graphics cards - GPU and memory supplies  
• ASIC power supplies  
• Embedded processor and I/O supplies  
• DSP supplies  
28  
27  
26  
25  
24  
23  
22  
GNDP  
5VSBY  
GNDQ  
GNDQ  
VTT  
1
2
3
4
5
6
7
21 PGOOD  
Ordering Information  
20  
19  
PHASE  
DRIVE2  
TEMP. RANGE  
o
PKG.  
DWG. #  
PART NUMBER  
( C)  
PACKAGE  
GND  
29  
18 FB2  
ISL6532ACR  
0 to 70  
0 to 70  
28 Ld 6x6 QFN  
L28.6x6  
L28.6x6  
ISL6532ACRZ  
(See Note)  
28 Ld 6x6 QFN  
(Pb-free)  
17  
16  
15  
GNDA  
COMP  
FB  
VTT  
*Add “-T” suffix to part number for tape and reel packaging.  
VDDQ  
NOTE: Intersil Pb-free products employ special Pb-free material sets; molding  
compounds/die attach materials and 100% matte tin plate termination finish, which  
is 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-020B.  
8
9
10  
11  
12  
13  
14  
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.  
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.  
Copyright © Intersil Americas Inc. 2002-2004. All Rights Reserved  
1
All other trademarks mentioned are the property of their respective owners.  
Block Diagram  
P5VSBY  
VDDQ S3  
S3#  
S5#  
5VSBY  
VOLTAGE  
REFERENCE  
REGULATOR  
+
-
0.800V  
0.680V (-15%)  
0.920V (+15%)  
5V  
VDDQ(3)  
VTTSNS  
12VCC  
POR  
EA2  
+
-
DRIVE2  
650OUTPUT  
IMPEDANCE  
VTT  
REG  
-
-
+
FB2  
+
VTT(2)  
GNDQ  
S3  
UV/OV3  
NCH  
UV/OV  
PWM ENABLE  
SLEEP,  
SOFT-START,  
PGOOD,  
AND FAULT  
LOGIC  
S0  
DISABLE  
S0/S3  
12V  
SOFT-START  
POR  
{
+
-
R
U
+
-
P12V  
PWM  
EA1  
PWM  
LOGIC  
VREF_IN  
UGATE  
COMP  
OSCILLATOR  
250kHz  
PHASE  
LGATE  
+
-
{
UV/OV1  
-
+
OC  
COMP  
20µA  
R
L
+
-
GNDA  
+
-
UV/OV2  
VREF_OUT  
PGOOD  
FB  
OCSET  
GNDP  
COMP  
ISL6532A  
Simplified Power System Diagram  
12V  
5VSBY  
5V  
ISL6532A  
NCH  
Q1  
SLP_S3  
SLP_S5  
SLEEP  
STATE  
LOGIC  
V
DDQ  
PWM  
CONTROLLER  
+
Q2  
5VSBY/3V3SBY  
STANDBY  
LDO  
V
DDQ  
V
V
REF  
TT  
LINEAR  
CONTROLLER  
Q3  
VTT  
REGULATOR  
V
AGP  
+
+
Typical Application - 5V or 3.3V Input  
5VSBY  
+12V  
+3.3V  
C
BP  
+5V or +3.3V  
R
NCH  
PGOOD  
S3#  
S5#  
V
DDQ  
SLP_S3  
SLP_S5  
NCH  
Q4  
V
REF  
+
VREF_OUT  
OCSET  
C
IN  
R
OCSET  
VREF_IN  
+
UGATE  
PHASE  
Q1  
Q2  
V
DDQ  
2.5V  
L
OUT  
+
ISL6532A  
VTT  
VTT  
LGATE  
V
C
TT  
VDDQ_OUT  
VDDQ  
VDDQ  
VDDQ  
+
C
VTT_OUT  
V
DDQ  
GNDQ  
GNDQ  
VTTSNS  
DRIVE2  
Q3  
FB  
COMP  
V
AGP  
1.5V  
FB2  
+
GNDP  
GNDA  
C
OUT2  
3
ISL6532A  
Typical Application - Input From 5V Dual  
5VSBY  
+12V  
+3.3V  
C
BP  
5V Dual  
PGOOD  
S3#  
S5#  
V
DDQ  
SLP_S3  
SLP_S5  
NCH  
V
REF  
+
VREF_OUT  
VREF_IN  
OCSET  
C
IN  
R
OCSET  
UGATE  
PHASE  
Q1  
Q2  
V
DDQ  
2.5V  
L
OUT  
+
ISL6532A  
VTT  
VTT  
LGATE  
V
TT  
C
VDDQ_OUT  
VDDQ  
VDDQ  
VDDQ  
+
C
VTT_OUT  
V
DDQ  
GNDQ  
GNDQ  
VTTSNS  
DRIVE2  
Q3  
FB  
V
COMP  
AGP  
1.5V  
FB2  
+
GNDP  
GNDA  
C
OUT2  
4
ISL6532A  
Absolute Maximum Ratings  
Thermal Information  
o
o
5VSBY, P5VSBY . . . . . . . . . . . . . . . . . . . . . . . . .GND - 0.3V to +7V  
P12V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .GND - 0.3V to +14V  
UGATE, LGATE, NCH . . . . . . . . . . . . . . GND - 0.3V to P12V + 0.3V  
All other Pins . . . . . . . . . . . . . . . . . . . . GND - 0.3V to 5VCC + 0.3V  
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LEVEL 1  
Thermal Resistance (Typical, Notes 1, 2) θJA ( C/W) θJC ( C/W)  
QFN Package . . . . . . . . . . . . . . . . . . . 32  
Maximum Junction Temperature (Plastic Package) . . . . . . . 150 C  
5
o
o
o
Maximum Storage Temperature Range. . . . . . . . . . -65 C to 150 C  
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300 C  
o
(SOIC - Lead Tips Only)  
Recommended Operating Conditions  
Supply Voltage on 5VSBY . . . . . . . . . . . . . . . . . . . . . . . . +5V ±10%  
Supply Voltage on P12V . . . . . . . . . . . . . . . . . . . . . . . . +12V ±10%  
Supply Voltage onP5VSBY . . . . . . . . . . . . . . . . . . . . . . . +5V ±10%  
o
o
Ambient Temperature Range. . . . . . . . . . . . . . . . . . . . 0 C to 70 C  
o
o
Junction Temperature Range. . . . . . . . . . . . . . . . . . . 0 C to 125 C  
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.  
NOTES:  
1. θ 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. For θ , 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 and Simplified Power System  
Diagrams and Typical Application Schematics  
PARAMETER  
5VSBY SUPPLY CURRENT  
Nominal Supply Current  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
I
I
S3# & S5# HIGH, UGATE/LGATE Open  
3.00  
3.50  
5.25  
-
7.25  
4.75  
mA  
mA  
CC_S0  
CC_S3  
S3# LOW, S5# HIGH, UGATE/LGATE  
Open  
I
S5# LOW, S3# Dont’t Care,  
UGATE/LGATE Open  
300  
-
800  
µA  
CC_S5  
POWER-ON RESET  
Rising 5VSBY POR Threshold  
Falling 5VSBY POR Threshold  
Rising P12V POR Threshold  
Falling P12V POR Threshold  
OSCILLATOR AND SOFT-START  
PWM Frequency  
4.00  
3.60  
10.0  
8.80  
-
-
-
-
4.35  
3.95  
10.5  
9.75  
V
V
V
V
f
220  
-
250  
280  
-
kHz  
V
OSC  
Ramp Amplitude  
V  
1.5  
OSC  
Error Amp Reset Time  
VDDQ Soft-Start Interval  
REFERENCE VOLTAGE  
Reference Voltage  
t
Mechanical Off/S5 to S0  
Mechanical Off/S5 to S0  
6.5  
6.5  
-
-
9.5  
9.5  
ms  
ms  
RESET  
t
SS  
V
-
0.800  
-
-
V
REF  
System Accuracy  
-2.0  
+2.0  
%
PWM CONTROLLER ERROR AMPLIFIER  
DC Gain  
Guaranteed By Design  
-
15  
-
80  
-
-
-
-
dB  
Gain-Bandwidth Product  
Slew Rate  
GBWP  
SR  
MHz  
V/µs  
6
STATE LOGIC  
S3# Transition Level  
V
V
-
-
1.5  
1.5  
-
-
V
V
S3  
S5  
S5# Transition Level  
5
ISL6532A  
Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted. Refer to Block and Simplified Power System  
Diagrams and Typical Application Schematics (Continued)  
PARAMETER  
PWM CONTROLLER GATE DRIVERS  
UGATE and LGATE Source  
UGATE and LGATE Sink  
NCH BACKFEED CONTROL  
NCH Current Sink  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
I
I
-
-
-0.8  
0.8  
-
-
A
A
GATE  
GATE  
I
NCH = 0.8V  
-
-
6
mA  
V
NCH  
NCH Trip Level  
V
9.0  
9.5  
10.0  
NCH  
VDDQ STANDBY LDO  
Output Drive Current  
P5VSBY = 5.0V  
P5VSBY = 3.3V  
-
-
-
-
650  
550  
mA  
mA  
VTT REGULATOR  
Upper Divider Impedance  
Lower Divider Impedance  
VREF_OUT Buffer Source Current  
R
-
-
2.5  
2.5  
-
-
-
kΩ  
kΩ  
mA  
A
U
R
L
I
-
2
3
VREF_OUT  
Maximum V Load Current  
TT  
I
Periodic load applied with 30% duty cycle  
and 10ms period using ISL6532AEVAL1  
evaluation board (see Application Note  
AN1056)  
-3  
-
VTT_MAX  
LINEAR REGULATOR  
DC GAIN  
Guaranteed By Design  
-
15  
-
80  
-
-
dB  
MHz  
V/µs  
V
Gain Bandwidth Product  
Slew Rate  
GBWP  
SR  
-
6
-
DRIVE2 High Output Voltage  
DRIVE2 Low Output Voltage  
DRIVE2 High Output Source Current  
DRIVE2 Low Output Sink Current  
PGOOD  
10.0  
-
10.2  
0.16  
-1.4  
1.3  
-
0.40  
V
-.5  
.85  
-
-
mA  
mA  
PGOOD Rising Threshold  
PGOOD Falling Threshold  
PROTECTION  
V
V
V
S0  
S0  
-
-
57.5  
45.0  
-
-
%
%
VTTSNS/ VDDQ  
V
VTTSNS/ VDDQ  
OCSET Current Source  
VDDQ OV Level  
I
17  
-
20  
115  
85  
22  
-
µA  
%
OCSET  
V
V
/V  
S0  
FB REF  
VDDQ UV Level  
/V  
S0  
-
-
%
FB REF  
/V  
Linear Regulator OV Level  
Linear Regulator UV Level  
Thermal Shutdown Limit  
V
V
S0  
-
115  
85  
-
%
FB2 REF  
/V  
S0  
-
-
%
FB2 REF  
T
By Design  
-
140  
-
°C  
SD  
6
ISL6532A  
The FB pin is also monitored for under and over-voltage  
events.  
Functional Pin Description  
5VSBY (Pin 2)  
PHASE (Pin 20)  
5VSBY is the bias supply of the ISL6532A. It is typically  
connected to the 5V standby rail of an ATX power supply.  
During S4/S5 sleep states the ISL6532A enters a reduced  
Connect this pin to the upper MOSFET’s source. This pin is  
used to monitor the voltage drop across the upper MOSFET  
for over-current protection.  
power mode and draws less than 1mA (I  
) from the  
CC_S5  
5VSBY supply. The supply to 5VSBY should be locally  
bypassed using a 0.1µF capacitor.  
OCSET (Pin 12)  
Connect a resistor (R  
) from this pin to the drain of the  
OCSET  
P12V (Pin 25)  
upper MOSFET. R  
, an internal 20µA current source  
OCSET  
(I  
), and the upper MOSFET on-resistance (r  
)
P12V provides the gate drive to the switching MOSFETs of  
OCSET DS(ON)  
set the converter over-current (OC) trip point according to  
the following equation:  
the PWM power stage. The V regulation circuit and the  
TT  
Linear Driver are also powered by P12V. P12V is not  
required except during S0/S1/S2 operation. P12V is typically  
connected to the +12V rail of an ATX power supply.  
I
xR  
OCSET  
OCSET  
I
= -------------------------------------------------  
PEAK  
r
DS(ON)  
5VSBY (Pin 11)  
An over-current trip cycles the soft-start function.  
This pin provides the V  
state. The regulator is capable of providing standby V  
power from either the 5VSBY or 3.3VSBY rail. It is  
recommended that the 5VSBY rail be used as the output  
current handling capability of the standby LDO is higher than  
with the 3.3VSBY rail.  
output power during S3 sleep  
DDQ  
VDDQ (Pins 7, 8, 9)  
DDQ  
The VDDQ pins should be connected externally together to  
the regulated V output. During S0/S1 states, the VDDQ  
DDQ  
pins serve as inputs to the V regulator and to the V  
Reference precision divider. During S3 state, the VDDQ pins  
serve as an output from the integrated standby LDO.  
TT TT  
GND, GNDA, GNDP, GNDQ (Pins 1, 3, 4, 17, 29)  
VTT (Pins 5, 6)  
The GND terminals of the ISL6532A provide the return path  
The VTT pins should be connect externally together. During  
for the V LDO, standby LDO and switching MOSFET gate  
TT  
S0/S1 states, the VTT pins serve as the outputs of the V  
TT  
drivers. High ground currents are conducted directly through  
the exposed paddle of the QFN package which must be  
electrically connected to the ground plane through a path as  
low in inductance as possible. GNDA is the Analog ground  
pin, GNDQ is the return for the VTT regulator and GNDP is  
the return for the upper and lower gate drives.  
linear regulator. During S3 state, the V regulator is  
TT  
disabled.  
VTTSNS (Pin 10)  
VTTSNS is used as the feedback for control of the V linear  
TT  
regulator. Connect this pin to the V output at the physical  
TT  
point of desired regulation.  
UGATE (Pin 26)  
UGATE drives the upper (control) FET of the V  
DDQ  
synchronous buck switching regulator. UGATE is driven  
between GND and P12V.  
VREF_OUT (Pin 13)  
VREF_OUT is a buffered version of V and also acts as the  
TT  
reference voltage for the V linear regulator. It is  
TT  
recommended that a minimum capacitance of 0.1µF is  
LGATE (Pin 27)  
connected between V  
between VREF_OUT and ground for proper operation.  
and VREF_OUT and also  
DDQ  
LGATE drives the lower (synchronous) FET of the V  
synchronous buck switching regulator. LGATE is driven  
between GND and P12V.  
DDQ  
VREF_IN (Pin 14)  
A capacitor, C , connected between VREF_IN and ground  
SS  
FB (Pin 15) and COMP (Pin 16)  
is required. This capacitor and the parallel combination of  
The V  
DDQ  
switching regulator employs a single voltage  
the Upper and Lower Divider Impedance (R ||R ), sets the  
U
L
control loop. FB is the negative input to the voltage loop error  
amplifier. The positive input of the error amplifier is  
connected to a precision 0.8V reference and the output of  
time constant for the start up ramp when transitioning from  
S3 to S0/S1/S2.  
the error amplifier is connected to the COMP pin. The V  
output voltage is set by an external resistor divider  
DDQ  
The minimum value for C can be found through the  
SS  
following equation:  
connected to FB. With a properly selected divider, V  
can  
DDQ  
C
V  
DDQ  
VTTOUT  
be set to any voltage between the power rail (reduced by  
converter losses) and the 0.8V reference. Loop  
compensation is achieved by connecting an AC network  
across COMP and FB.  
------------------------------------------------  
>
C
SS  
||  
10 2A R  
R
L
U
7
ISL6532A  
The calculated capacitance, C , will charge the output  
SS  
ACPI compliance is realized through the SLP_S3 and  
SLP_S5 sleep signals and through monitoring of the 12V  
ATX bus.  
capacitor bank on the V rail in a controlled manner without  
TT  
reaching the current limit of the V LDO.  
TT  
NCH (Pin 22)  
Initialization  
NCH is an open-drain output that controls the MOSFET  
The ISL6532A automatically initializes upon receipt of input  
power. Special sequencing of the input supplies is not  
necessary. The Power-On Reset (POR) function continually  
monitors the input bias supply voltages. The POR monitors  
the bias voltage at the 5VSBY and P12V pins. The POR  
function initiates soft-start operation after the bias supply  
voltages exceed their POR thresholds.  
blocking backfeed from V  
to the input rail during sleep  
DDQ  
states. A 2kor larger resistor is to be tied between the 12V  
rail and the NCH pin. Until the voltage on the NCH pin  
reaches the NCH trip level, the PWM is disabled.  
If NCH is not actively utilized, it still must be tied to the 12V  
rail through a resistor. For systems using 5V dual as the  
input to the switching regulator, a time constant, in the form  
of a capacitor, can be added to the NCH pad to delay start of  
the PWM switcher until the 5V dual has switched from  
5VSBY to 5VATX.  
ACPI State Transitions  
Cold Start (S4/S5 to S0 Transition)  
At the onset of a mechanical start, the ISL6532A receives it’s  
bias voltage from the 5V Standby bus (5VSBY). As soon as  
the SLP_S3 and SLP_S5 have transitioned HIGH, the  
ISL6532A starts an internal counter. Following a cold start or  
any subsequent S4/S5 state, state transitions are ignored  
until the system enters S0/S1. None of the regulators will  
begin the soft start procedure until the 5V Standby bus has  
PGOOD (Pin 21)  
Power Good is an open-drain logic output that changes to a  
logic low if any of the three regulators are out of regulation in  
S0/S1/S2 state. PGOOD will always be low in any state other  
than S0/S1/S2.  
exceeded POR, the 12V bus has exceeded POR and V  
SLP_S5# (Pin 24)  
NCH  
has exceeded the trip level.  
This pin accepts the SLP_S5# sleep state signal.  
Once all of these conditions are met, the PWM error  
amplifier will first be reset by internally shorting the COMP  
pin to the FB pin. This reset lasts for 2048 clock cycles,  
SLP_S3# (Pin 23)  
This pin accepts the SLP_S3# sleep state signal.  
which is typically 8.2ms (one clock cycle = 1/f  
digital soft start sequence will then begin.  
). The  
OSC  
FB2 (Pin 18)  
Connect the output of the external linear regulator to this pin  
through a properly sized resistor divider. The voltage at this  
pin is regulated to 0.8V. This pin is monitored for under and  
over-voltage events.  
The PWM error amplifier reference input 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  
DRIVE2 (Pin 19)  
capacitor(s). The internal VTT LDO will also soft start  
through the reference that tracks the output of the PWM  
regulator. The reference for the AGP LDO controller will rise  
relative to the soft start reference. The soft start lasts for  
2048 clock cycles, which is typically 8.2ms. This method  
provides a rapid and controlled output voltage rise.  
Connect this pin to the gate terminal of an external N-  
Channel MOSFET transistor. This pin provides the gate  
voltage for the linear regulator pass transistor. It also  
provides a means of compensating the error amplifier for  
applications requiring the transient response of the linear  
regulator to be optimized.  
Figure 1 shows the soft start sequence for a typical cold  
Functional Description  
start. Due to the soft start capacitance, C , on the  
VREF_IN pin, the S5 to S0 transition profile of the V rail  
TT  
will have a more rounded features at the start and end of the  
SS  
Overview  
The ISL6532A provides complete control, drive, protection  
and ACPI compliance for a regulator powering DDR memory  
systems. It is primarily designed for computer applications  
powered from an ATX power supply. A 250kHz Synchronous  
Buck Regulator with a precision 0.8V reference provides the  
proper Core voltage to the system memory of the computer.  
An internal LDO regulator with the ability to both sink and  
source current and an externally available buffered reference  
soft start whereas the V  
profile has distinct starting and  
DDQ  
ending points to the ramp up.  
By directly monitoring 12VATX and the SLP_S3 and SLP_S5  
signals the ISL6532A can achieve PGOOD status  
significantly faster than other devices that depend on  
Latched_Backfeed_Cut for timing.  
Active to Sleep (S0 to S3 Transition)  
that tracks the V  
output by 50% provides the V  
DDQ  
TT  
When SLP_S3 goes LOW with SLP_S5 still HIGH, the  
ISL6532A will disable the V linear regulator and the AGP  
LDO controller. The V  
DDQ  
termination voltage. The ISL6532A also features an LDO  
regulator for 1.5V AGP Video and Core voltage.  
TT  
standby regulator will be enabled  
8
ISL6532A  
should be noted that the soft start profile of the V LDO  
TT  
output will vary according to the value of the capacitor on the  
VREF_IN pin.  
S3  
S5  
12VATX 2V/DIV  
5VSBY  
1V/DIV  
V
S3  
DDQ  
500mV/DIV  
S5  
V
AGP  
500mV/DIV  
12VATX 2V/DIV  
V
TT  
V
DDQ  
500mV/DIV  
500mV/DIV  
V
AGP  
500mV/DIV  
PGOOD  
5V/DIV  
V
TT_FLOAT  
V
TT  
2048 CLOCK  
CYCLES  
2048 CLOCK  
CYCLES  
500mV/DIV  
SOFT START ENDS  
PGOOD COMPARATOR  
ENABLED  
SOFT START  
INITIATES  
12V POR  
PGOOD  
5V/DIV  
FIGURE 1. TYPICAL COLD START  
2048 CLOCK  
CYCLES  
PGOOD COMPARATOR  
ENABLED  
and the V  
switching regulator will be disabled. NCH is  
DDQ  
12V POR  
pulled low to disable the backfeed blocking MOSFET.  
PGOOD will also transition LOW. When V is disabled, the  
FIGURE 2. TYPICAL S3 to S0 STATE TRANSITION  
TT  
internal reference for the V regulator is internally shorted  
TT  
to the V rail. This allows the V rail to float. When  
Active to Shutdown (S0 to S5 Transition)  
TT  
TT  
floating, the voltage on the V rail will depend on the  
leakage characteristics of the memory and MCH I/O pins. It  
is important to note that the V rail may not bleed down to 0V.  
TT  
TT  
When the system transitions from active, S0, state to  
shutdown, S4/S5, state, the ISL6532A IC disables all  
regulators and forces the PGOOD pin and the NCH pin  
LOW.  
The V  
DDQ  
rail will be supported in the S3 state through the  
LDO. When S3 transitions LOW, the Standby  
standby V  
DDQ  
V
Over Current Protection (S0 State)  
DDQ  
regulator is immediately enabled. The switching regulator is  
disabled synchronous to the switching waveform. The shut  
off time will range between 4 and 8us. The standby LDO is  
capable of supporting up to 650mA of load with P5VSBY tied  
to the 5V Standby Rail. The standby LDO may receive input  
from either the 3.3V Standby rail or the 5V Standby rail  
through the P5VSBY pin. It is recommended that the 5V  
Standby rail be used as the current delivery capability of the  
LDO is greater.  
The over-current function protects the switching converter  
from a shorted output by using the upper MOSFET on-  
resistance, r  
, to monitor the current. This method  
DS(ON)  
enhances the converter’s efficiency and reduces cost by  
eliminating a current sensing resistor.  
The over-current function cycles the soft-start function in a  
hiccup mode to provide fault protection. A resistor (R  
)
OCSET  
programs the over-current trip level (see Typical Application  
diagrams on pages 3 and 4). An internal 20µA (typical)  
Sleep to Active (S3 to S0 Transition)  
current sink develops a voltage across R  
that is  
OCSET  
When SLP_S3 transitions from LOW to HIGH with SLP_S5  
held HIGH and after the 12V rail exceeds POR, the  
referenced to the converter input voltage. When the voltage  
across the upper MOSFET (also referenced to the converter  
ISL6532A will enable the V  
switching regulator, disable  
DDQ  
standby regulator, enable the V LDO and force  
input voltage) exceeds the voltage across R  
, the over-  
OCSET  
the V  
DDQ  
TT  
current function initiates a soft-start sequence. The initiation  
the NCH pin to a high impedance state turning on the  
blocking MOSFET. The AGP LDO goes through a 2048 clock  
cycle soft-start. The internal short between the V  
reference and the V rail is released. Upon release of the  
TT  
short, the capacitor on VREF_IN is then charged up through  
the internal resistor divider network. The V output will  
of soft start will affect all regulators. The V regulator is  
TT  
directly affected as it receives it’s reference from V  
. The  
DDQ  
TT  
AGP LDO will also be soft started, and as such, the AGP  
LDO voltage will be disabled while the V  
disabled.  
regulator is  
DDQ  
TT  
Figure 3 illustrates the protection feature responding to an  
over current event. At time T0, an over current condition is  
sensed across the upper MOSFET. As a result, the regulator  
is quickly shutdown and the internal soft-start function  
begins producing soft-start ramps. The delay interval seen  
follow this capacitor charge up, and acting as the S3 to S0  
transition soft start for the V rail. The PGOOD comparator  
TT  
is enabled only after 2048 clock cycles, or typically 8.2ms,  
have passed following the S3 transition to a HIGH state.  
Figure 2 illustrates a typical state transition from S3 to S0. It  
9
ISL6532A  
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. The output is brought back  
into regulation by time T2, as long as the over current event  
has cleared.  
For an equation for the ripple current see the section under  
component guidelines titled ‘Output Inductor Selection’.  
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.  
Had the cause of the over current still been present after the  
delay interval, the over current condition would be sensed  
and the regulator 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.  
Over/Under Voltage Protection  
All three regulators are protected from faults through internal  
Over/Under voltage detection circuitry. If the any rail falls  
below 85% of the targeted voltage, then an undervoltage  
event is tripped. An under voltage will disable all three  
regulators for a period of 3 soft-start cycles, after which a  
normal soft-start is initiated. If the output is still under 85% of  
target, the regulators will continue to be disabled and soft-  
started in a hiccup mode until the fault is cleared. This  
protection feature works much the same as the VDDQ PWM  
over current protection works. See Figure 3.  
V
DDQ  
V
AGP  
If the any rail exceeds 115% of the targeted voltage, then all  
three outputs are immediately disabled. The ISL6532A will  
not re-enable the outputs until either the bias voltage is  
toggled in order to initiate a POR or the S5 signal is forced  
LOW and then back to HIGH.  
V
TT  
500mV/DIV  
Thermal Protection (S0/S3 State)  
INTERNAL SOFT-START FUNCTION  
DELAY INTERVAL  
If the ISL6532A IC junction temperature reaches a nominal  
o
temperature of 140 C, all regulators will be disabled. The  
ISL6532A will not re-enable the outputs until the junction  
o
temperature drops below 110 C and either the bias voltage  
is toggled in order to initiate a POR or the SLP_S5 signal is  
forced LOW and then back to HIGH.  
T0  
T1  
T2  
Shoot-Through Protection  
TIME  
A shoot-through condition occurs when both the upper and  
lower MOSFETs are turned on simultaneously, effectively  
shorting the input voltage to ground. To protect from a shoot-  
through condition, the ISL6532A incorporates specialized  
circuitry which insures that complementary MOSFETs are  
not ON simultaneously.  
FIGURE 3. V  
V
OVER CURRENT PROTECTION AND  
DDQ  
/V  
LDO UNDER VOLTAGE PROTECTION  
TT AGP  
RESPONSES  
The over-current function will trip at a peak inductor current  
(I  
determined by:  
PEAK)  
The adaptive shoot-through protection utilized by the V  
DDQ  
I
x R  
OCSET  
OCSET  
I
= ----------------------------------------------------  
PEAK  
regulator looks at the lower gate drive pin, LGATE, and the  
upper gate drive pin, UGATE, to determine whether a  
MOSFET is ON or OFF. If the voltage from UGATE or from  
LGATE to GND is less than 0.8V, then the respective  
MOSFET is defined as being OFF and the other MOSFET is  
r
DS(ON)  
where I  
is the internal OCSET current source (20µA  
OCSET  
typical). The OC trip point varies mainly due to the MOSFET  
variations. To avoid over-current tripping in the  
normal operating load range, find the R  
the equation above with:  
r
DS(ON)  
allowed to turned ON. This method allows the V  
regulator to both source and sink current.  
DDQ  
resistor from  
OCSET  
Since the voltage of the MOSFET gates are being measured  
to 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.  
1. The maximum r  
temperature.  
at the highest junction  
DS(ON)  
2. The minimum I  
from the specification table.  
OCSET  
3. Determine I  
for:  
PEAK  
(∆I)  
----------  
I
> I  
+
,where I is  
PEAK  
OUT(MAX)  
2
the output inductor ripple current.  
10  
ISL6532A  
12V  
ATX  
Application Guidelines  
P12V  
C
BP  
Layout Considerations  
GNDP  
V
IN_DDR  
Layout is very important in high frequency switching  
ISL6532A  
converter design. With power devices switching efficiently at  
250kHz, 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 over-voltage stress. Careful component  
layout and printed circuit board design minimizes these  
voltage spikes.  
NCH  
5VSBY  
P5VSBY  
5VSBY  
C
IN  
C
BP  
GNDP  
L
UGATE  
PHASE  
OUT  
Q
1
V
DDQ  
As an example, consider the turn-off transition of the control  
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.  
C
OUT1  
LGATE  
COMP  
Q
2
C
2
C
1
R
2
R
1
FB  
C
R
3
3
R
4
VDDQ(3)  
VTT(2)  
V
DDQ  
There are two sets of critical components in the ISL6532A  
switching converter. 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.  
V
TT  
C
OUT2  
V
IN_AGP  
Q
3
DRIVE2  
FB2  
R
V
AGP  
5
A multi-layer printed circuit board is recommended. Figure 4  
shows the connections of the critical components in the  
GND PAD  
R
6
C
OUT3  
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  
nodes. Use copper filled polygons on the top and bottom  
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.  
KEY  
ISLAND ON POWER PLANE LAYER  
ISLAND ON CIRCUIT PLANE LAYER  
VIA CONNECTION TO GROUND PLANE  
FIGURE 4. PRINTED CIRCUIT BOARD POWER PLANES  
AND ISLANDS  
possible. Position the output inductor and output capacitors  
between the upper and lower MOSFETs and the load.  
The critical small signal components include any bypass  
capacitors, feedback components, and compensation  
components. Place the PWM converter compensation  
components close to the FB and COMP pins. The feedback  
resistors should be located as close as possible to the FB  
pin with vias tied straight to the ground plane as required.  
In order to dissipate heat generated by the internal V LDO,  
TT  
the ground pad, pin 29, should be connected to the internal  
ground plane through at least four vias. This allows the heat  
to move away from the IC and also ties the pad to the ground  
plane through a low impedance path.  
Feedback Compensation - PWM Buck Converter  
Figure 5 highlights the voltage-mode control loop for a  
synchronous-rectified buck converter. The output voltage  
The switching components should be placed close to the  
ISL6532A first. Minimize the length of the connections  
(V  
) is regulated to the Reference voltage level. The error  
OUT  
between the input capacitors, C , and the power switches  
IN  
amplifier output (V ) is compared with the oscillator (OSC)  
E/A  
by placing them nearby. Position both the ceramic and bulk  
input capacitors as close to the upper MOSFET drain as  
triangular wave to provide a pulse-width modulated (PWM)  
wave with an amplitude of V at the PHASE node.  
IN  
11  
ISL6532A  
ND  
The PWM wave is smoothed by the output filter (L and C ).  
5. Place 2  
Pole at Half the Switching Frequency.  
O
O
V
6. Check Gain against Error Amplifier’s Open-Loop Gain.  
7. Estimate Phase Margin - Repeat if Necessary.  
DRIVER  
IN  
OSC  
PWM  
L
O
COMPARATOR  
V
DDQ  
Compensation Break Frequency Equations  
-
DRIVER  
PHASE  
+
V  
OSC  
C
O
1
1
F
F
= -----------------------------------  
F
F
= --------------------------------------------------------  
Z1  
P1  
2π x R x C  
C
x C  
2
2
2
1
ESR  
(PARASITIC)  
---------------------  
2π x R  
x
2
C
+ C  
1
2
Z
FB  
1
1
V
= ------------------------------------------------------  
= -----------------------------------  
E/A  
Z2  
P2  
2π x (R + R ) x C  
2π x R x C  
1
3
3
3
3
Z
-
IN  
+
REFERENCE  
Figure 6 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 6. Using the above guidelines should  
give a Compensation Gain similar to the curve plotted. The  
open loop error amplifier gain bounds the compensation  
ERROR  
AMP  
DETAILED COMPENSATION COMPONENTS  
Z
FB  
V
DDQ  
C
1
Z
IN  
C
C
R
R
3
2
3
2
gain. Check the compensation gain at F with the  
P2  
capabilities of the error amplifier. The Closed Loop Gain is  
constructed on the graph of Figure 6 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.  
R
1
COMP  
FB  
-
+
R
4
ISL6532A  
REFERENCE  
The compensation gain uses external impedance networks  
R
1
V
= 0.8 × 1 + ------  
Z
and Z to provide a stable, high bandwidth (BW) overall  
DDQ  
FB  
IN  
R
4
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.  
FIGURE 5. VOLTAGE-MODE BUCK CONVERTER  
COMPENSATION DESIGN AND OUTPUT  
VOLTAGE SELECTION  
The modulator transfer function is the small-signal transfer  
function of V /V . This function is dominated by a DC  
OUT E/A  
Gain and the output filter (L and C ), with a double pole  
100  
F
F
P1  
F
F
P2  
Z2  
Z1  
O
O
break frequency at F and a zero at F  
the modulator is simply the input voltage (V ) divided by the  
. The DC Gain of  
80  
60  
40  
20  
0
LC ESR  
OPEN LOOP  
ERROR AMP GAIN  
IN  
peak-to-peak oscillator voltage V  
OSC  
.
20LOG  
(R /R )  
Modulator Break Frequency Equations  
2
1
20LOG  
1
1
(V /V  
)
F
= ------------------------------------------  
F
= -------------------------------------------  
IN OSC  
LC  
ESR  
2π x ESR x C  
2π x  
L
x C  
O O  
O
COMPENSATION  
GAIN  
MODULATOR  
GAIN  
-20  
-40  
-60  
The compensation network consists of the error amplifier  
(internal to the ISL6532A) and the impedance networks Z  
CLOSED LOOP  
GAIN  
IN  
F
LC  
F
and Z . The goal of the compensation network is to provide  
ESR  
100K  
FREQUENCY (Hz)  
FB  
10  
100  
1K  
10K  
1M  
10M  
a closed loop transfer function with the highest 0dB crossing  
frequency (f  
) and adequate phase margin. Phase margin  
is the difference between the closed loop phase at f and  
0dB  
FIGURE 6. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN  
0dB  
180 degrees. The equations below relate the compensation  
Feedback Compensation - AGP LDO Controller  
network’s poles, zeros and gain to the components (R , R ,  
1
2
R , C , C , and C ) in Figure 5. Use these guidelines for  
locating the poles and zeros of the compensation network:  
Figure 7 shows the AGP LDO power and control stage. This  
LDO, which uses a MOSFET as the linear pass element,  
requires feedback compensation to insure stability of the  
system. The LDO requires compensation because of the  
output impedance of the error amplifier.  
3
1
2
3
1. Pick Gain (R /R ) for desired converter bandwidth.  
2
1
ST  
2. Place 1 Zero Below Filter’s Double Pole (~75% F ).  
LC  
ND  
3. Place 2  
Zero at Filter’s Double Pole.  
ST  
4. Place 1 Pole at the ESR Zero.  
12  
ISL6532A  
Component Selection Guidelines  
ISL6532A  
V
DDQ  
Output Capacitor Selection - PWM Buck Converter  
0.8V  
REFERENCE  
An output capacitor is required to filter the inductor current  
and supply the load transient current. The filtering  
requirements are a function of the switching frequency 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.  
650Ω  
DRIVE2  
+
-
OUTPUT  
IMPEDANCE  
V
C
R
AGP  
25  
10  
FB2  
R
8
R
9
DDR memory systems are capable of producing transient  
load rates above 1A/ns. 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.  
ESR  
OUT  
R
LOAD  
+
R
C
8
V
= 0.8 × 1 + ------  
AGP  
R
9
FIGURE 7. COMPENSATION AND OUTPUT VOLTAGE  
SELECTION OF THE LINEAR  
To properly compensate the LDO system, a 100k1%  
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.  
resistor and a 680pF X5R ceramic capacitor, represented as  
R10 and C25 in Figure 7, are used. This compensation will  
insure a stable system with any MOSFET given the following  
conditions:  
τ = C  
ESR > 10µs  
OUT  
R
= R = 249Ω  
8
FB  
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 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.  
Maximum bandwidth will be realized at full load while  
minimum bandwidth will be realized at no load. Bandwidth at  
no load will be maximized as τ becomes closer to 10µs.  
Output Voltage Selection  
The output voltage of the V  
PWM converter can be  
DDQ  
programmed to any level between V and the internal  
IN  
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 5. 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. Depending on the value chosen  
for R1, R4 can be calculated based on the following equation:  
R1 × 0.8V  
R4 = -----------------------------------  
V
- 0.8V  
Output Capacitor Selection - LDO Regulators  
DDQ  
The output capacitors used in LDO regulators are used to  
provide dynamic load current. The amount of capacitance  
and type of capacitor should be chosen with this criteria in  
mind.  
If the output voltage desired is 0.8V, simply route V  
to the FB pin through R1, but do not populate R4.  
back  
DDQ  
The output voltage for the internal V linear regulator is set  
TT  
internal to the ISL6532A to track the V  
voltage by 50%.  
DDQ  
Output Inductor Selection  
There is no need for external programming resistors.  
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:  
As with the V PWM regulator, the AGP linear regulator  
DDQ  
output voltage is set by means of an external resistor divider  
as shown in Figure 7. For stability concerns described  
earlier, the recommended value of the feedback resistor, R8,  
is 249. The voltage programming resistor, R9 can be  
calculated based on the following equation:  
V
- V  
OUT  
V
OUT  
IN  
Fs x L  
R
× 0.8V  
V = I x ESR  
OUT  
I =  
x
8
R
= ----------------------------------  
V
IN  
9
V
- 0.8V  
AGP  
13  
ISL6532A  
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.  
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 current rating. These  
capacitors must be capable of handling the surge-current at  
power-up. Some capacitor series available from reputable  
manufacturers are surge current tested.  
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  
ISL6532A 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 - PWM Buck Converter  
The ISL6532A requires 2 N-Channel power MOSFETs for  
switching power and a third MOSFET to block backfeed from  
V
to the Input in S3 Mode. These should be selected  
DDQ  
based upon r  
, gate supply requirements, and thermal  
DS(ON)  
management requirements.  
In high-current applications, the MOSFET power dissipation,  
package selection and heatsink are the dominant design  
factors. The power dissipation includes two loss  
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:  
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 switching losses  
seen when sinking current. 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 in part by the ISL6532A  
and do not significantly heat the MOSFETs. However, large  
L x I  
L x I  
TRAN  
TRAN  
OUT  
t
=
t
=
FALL  
RISE  
V
- V  
V
OUT  
IN  
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 - PWM Buck Converter  
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  
to supply the current needed each time the upper MOSFET  
turns on. Place the small ceramic capacitors physically close  
to the MOSFETs and between the drain of upper MOSFET  
and the source of lower MOSFET.  
gate-charge increases the switching interval, t  
which  
SW  
increases the MOSFET switching losses. 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 important parameters for the bulk input capacitance are  
the voltage rating and the RMS current rating. For reliable  
operation, select bulk capacitors with voltage and current  
ratings above the maximum input voltage and largest RMS  
current required by the circuit. Their voltage rating should be  
at least 1.25 times greater than the maximum input voltage,  
while a voltage rating of 1.5 times is a conservative  
guideline. For most cases, the RMS current rating  
Approximate Losses while Sourcing current  
2
1
--  
P
= Io × r  
× D + Io × V × t  
× f  
SW  
UPPER  
LOWER  
DS(ON)  
IN  
2
s
2
P
= Io x r  
x (1 - D)  
DS(ON)  
Approximate Losses while Sinking current  
2
P
= Io x r  
x D  
UPPER  
DS(ON)  
requirement for the input capacitor of a buck regulator is  
approximately 1/2 the DC load current.  
2
1
--  
P
= Io × r  
× (1 - D) + Io × V × t  
× f  
SW s  
LOWER  
DS(ON)  
IN  
2
Where: D is the duty cycle = V  
OUT  
/ V ,  
IN  
is the combined switch ON and OFF time, and  
The maximum RMS current required by the regulator may be  
closely approximated through the following equation:  
t
SW  
f is the switching frequency.  
s
2
VOUT  
-------------  
VIN  
VIN - VOUT VOUT  
2
1
12  
   
------  
----------------------------- -------------  
IRMS  
=
× IOUT  
+
×
×
   
VIN  
L × fs  
MAX  
MAX  
14  
ISL6532A  
ISL6532A Application Circuit  
MOSFET Selection - AGP LDO  
The main criteria for selection of the linear regulator pass  
transistor is package selection for efficient removal of heat.  
Select a package and heatsink that maintains the junction  
temperature below the rating with a maximum expected  
ambient temperature.  
Figure 8 shows an application circuit utilizing the ISL6532A.  
Detailed information on the circuit, including a complete Bill-  
of-Materials and circuit board description, can be found in  
Application Note AN1056.  
The power dissipated in the linear regulator is:  
P
I × (V - V  
)
OUT  
LINEAR  
O
IN  
where I is the maximum output current and V  
O
is the  
OUT  
nominal output voltage of the linear regulator.  
VCC5  
5VSBY  
VCC12  
R
1
+3.3V  
4.99kΩ  
C
17,18  
1µF  
Q
5
R
C
2
16  
1µF  
10.0kΩ  
L
PGOOD  
PGOOD  
S5#  
1
NCH  
2.1µH  
V
DDQ  
SLP_S5  
SLP_S3  
C
1000pF  
22  
S3#  
C
26  
0.1µF  
V
REF  
+
C
C
1-3  
4,5  
1µF  
OCSET  
VREF_OUT  
VREF_IN  
2200µF  
R
7
8.87kΩ  
C
0.1µF  
27  
V
UGATE  
PHASE  
Q
DDQ  
1,3  
C
19  
0.47µF  
2.5V 15A  
MAX  
V
DDQ  
L
2
C
+
6-8  
+
ISL6532A  
2.1µH  
V
C
TT  
1.25V  
20  
220µF  
1800µF  
VTT  
VTT  
C
22µF  
LGATE  
9-12  
Q
2,4  
VDDQ  
VDDQ  
VDDQ  
+
C
220µF  
21  
V
DDQ  
VTTSNS  
DRIVE2  
R
4
1.74kΩ  
GNDQ  
GNDQ  
Q
4
R
100kΩ  
10  
FB  
V
AGP  
1.5V  
C
C
R
5
22.6Ω  
COMP  
680pF  
25  
13  
56nF  
FB2  
C
15  
R
1000pF  
8
+
R
9
C
220µF  
23  
249Ω  
C
287Ω  
24  
1µF  
C
6.8nF  
R
14  
3
19.1kΩ  
R
6
825Ω  
FIGURE 8. DDR SDRAM AND AGP VOLTAGE REGULATOR USING THE ISL6532A  
15  
ISL6532A  
Quad Flat No-Lead Plastic Package (QFN)  
Micro Lead Frame Plastic Package (MLFP)  
L28.6x6  
28 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE  
(COMPLIANT TO JEDEC MO-220VJJC 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
0.23  
3.95  
3.95  
0.28  
0.35  
4.25  
4.25  
5, 8  
D
6.00 BSC  
-
D1  
D2  
E
5.75 BSC  
9
4.10  
7, 8  
6.00 BSC  
-
E1  
E2  
e
5.75 BSC  
9
4.10  
7, 8  
0.65 BSC  
-
k
0.25  
0.35  
-
-
-
-
L
0.60  
0.75  
0.15  
8
L1  
N
-
28  
7
7
-
10  
2
Nd  
Ne  
P
3
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  
16  

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