Intersil ISL6531CR-T Dual 5v synchronous buck pulse-width modulator (pwm) controller for ddram memory vddq and vtt termination Datasheet

ISL6531
®
Data Sheet
August 11, 2005
FN9053.2
Dual 5V Synchronous Buck Pulse-Width
Modulator (PWM) Controller for DDRAM
Memory VDDQ and VTT Termination
Features
The ISL6531 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
topology to efficiently generate 2.5V VDDQ for powering
DDRAM memory, VREF for DDRAM differential signalling,
and VTT for signal termination. The ISL6531 integrates all of
the control, output adjustment, monitoring and protection
functions into a single package.
• Excellent voltage regulation
- VDDQ = 2.5V ±2% over full operating range
- VREF = 1--- ⋅ V DDQ ±1% over full operating range
2
- VTT = VREF ± 30mV
The VDDQ output of the converter is maintained at 2.5V
through an integrated precision voltage reference. The VREF
output is precisely regulated to 1/2 the memory power
supply, with a maximum tolerance of ±1% over temperature
and line voltage variations. VTT accurately tracks VREF.
During V2_SD sleep mode, the VTT output is maintained by
a low power window regulator.
The ISL6531 provides simple, single feedback loop, voltagemode control with fast transient response for the VDDQ
regulator. The VTT regulator features internal compensation
that eases the design. It includes two phase-locked 300kHz
triangle-wave oscillators which are displaced 90o to minimize
interference between the two PWM regulators. The
regulators feature error amplifiers with a 15MHz gainbandwidth 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%.
The ISL6531 protects against overcurrent conditions by
inhibiting PWM operation. The ISL6531 monitors the current
in the VDDQ regulator by using the rDS(ON) of the upper
MOSFET which eliminates the need for a current sensing
resistor.
• Provides VDDQ, VREF, and VTT voltages for one- and twochannel DDRAM memory systems
• Supports ‘S3’ sleep mode
- VTT is held at 1--- ⋅ V DDQ via a low power window
2
regulator to minimize wake-up time
• Fast transient response
- Full 0% to 100% duty ratio
• Operates from +5V Input
• VTT regulator internally compensated
• Overcurrent fault monitor on VDD
- Does not require extra current sensing element
- Uses MOSFET’s rDS(ON)
• Drives inexpensive N-Channel MOSFETs
• Small converter size
- 300kHz fixed frequency oscillator
• 24 Lead, SOIC or 32 Lead, 5mm×5mm QFN
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• VDDQ, VTT, and VREF regulation for DDRAM memory
systems
- Main memory in AMD® Athlon™ and K8™, Pentium®
III, Pentium IV, Transmeta, PowerPC™, AlphaPC™, and
UltraSparc® based computer systems
• High-power tracking DC-DC regulators
Ordering Information
PART NUMBER
TEMP
RANGE(oC)
PACKAGE
PKG. DWG. #
ISL6531CB
0 to 70
24 Lead SOIC
M24.3
ISL6531CBZ
(See Note)
0 to 70
24 Lead SOIC
(Pb-free)
M24.3
ISL6531CR
0 to 70
32 Lead 5x5 QFN L32.5x5
ISL6530/31EVAL1 Evaluation Board
Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free plus anneal 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-020.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright © Intersil Americas Inc. 2003, 2005. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.
ISL6531
Pinouts
UGATE1
1
24 PGND1
BOOT1
2
23 LGATE1
BOOT1
UGATE1
UGATE1
PGND1
PGND1
LGATE1
PVCC1
32 LEAD 5X5 (QFN)
TOP VIEW
BOOT1
24 LEAD (SOIC)
TOP VIEW
22 PVCC1
32
31
30
29
28
27
26
25
PHASE1 3
21 OCSET/SD
VREF 4
24 PVCC1
VREF
2
23 OCSET/SD
FB1
3
22 V2_SD
COMP1
4
21 PGOOD
15 VCC
SENSE1
5
20 N/C
14 LGATE2
VREF_IN
6
19 SENSE2
GNDA
7
18 N/C
GNDA
8
17 VCC
19 PGOOD
6
18 N/C
SENSE1 7
17 SENSE2
VREF_IN 8
2
9
10
11
12
13
14
15
16
PGND2
LGATE2
VCC
13 PGND2
PGND2
BOOT2 11
UGATE2 12
UGATE2
PHASE2 10
BOOT2
16 N/C
9
BOOT2
GNDA
1
PHASE2
COMP1
PHASE 1
20 V2_SD
FB1 5
ISL6531
Block Diagram
OCSET/SD
PGOOD
VCC
POWER-ON
RESET (POR)
+
-
+
-
OVERCURRENT
SOFTSTART
BOOT1
X1.15
+
X0.85
+
X1.15
X0.85
+
-
40µA
UGATE1
PHASE1
ERROR
AMP
+
-
FB1
PWM
COMPARATOR
+
-
GATE
INHIBIT CONTROL
LOGIC
PWM
PVCC1
COMP1
0.8V
REFERENCE
SENSE1
LGATE1
OSCILLATOR
VREF_IN
PGND1
VREF
+
-
BOOT2
90o Phase
Shift
ERROR
AMP
Zf
UGATE2
+
Zc
+
PWM
COMPARATOR
PWM
INHIBIT
GATE
CONTROL
LOGIC
VCC
WINDOW
REGULATOR
SENSE2
PHASE2
LGATE2
V2_SD
PGND2
GND
3
ISL6531
Typical Application
+5V
PGOOD
ROCSET
VCC
DBOOT1
PGOOD
BOOT1
OCSET/SD
RESET
Q1
UGATE1
CBOOT1
GNDA
VDDQ
PHASE1
LOUT1
+5V
COUT1
PVCC1
V2_SD
SLEEP
Q2
LGATE1
ISL6531
VREF_IN
VREF
(.5xVDDQ)
PGND1
VREF
DBOOT2
COMP1
BOOT2
Q3
UGATE2
CBOOT2
PHASE2
VTT
LOUT2
LGATE2
FB1
PGND2
SENSE1
SENSE2
RFB1
FIGURE 1. TYPICAL APPLICATION FOR ISL6531
4
Q4
COUT2
ISL6531
Absolute Maximum Ratings
Thermal Information
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7.0V
Boot Voltage, VBOOTn - VPHASEn . . . . . . . . . . . . . . . . . . . . . . +7.0V
Input, Output or I/O Voltage . . . . . . . . . . . . GND -0.3V to VCC +0.3V
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2
Thermal Resistance
θJA (oC/W)
θJC (oC/W)
SOIC Package (Note 1) . . . . . . . . . . . .
65
N/A
QFN Package (Note 2). . . . . . . . . . . . .
33
4
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 150oC
Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC
(SOIC - Lead tips only)
For Recommended soldering conditions see Tech Brief TB389.
Operating Conditions
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±10%
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . 0oC to 70oC
Junction Temperature Range . . . . . . . . . . . . . . . . . . . . 0oC to 125oC
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. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
2. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. θJC, the
“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
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
OCSET/SD=VCC; UGATE1, UGATE2,
LGATE1, and LGATE2 Open
-
5
-
mA
OCSET/SD=0V
-
3
-
mA
VCC SUPPLY CURRENT
Nominal Supply
ICC
Shutdown Supply
POWER-ON RESET
Rising VCC Threshold
VOCSET/SD=4.5V
4.25
-
4.5
V
Falling VCC Threshold
VOCSET/SD=4.5V
3.75
-
4.0
V
VCC=5
275
300
325
kHz
SENSE1=2.5V
49.5
50.0
50.5
%SENSE1
-
-
2
%
-
0.8
-
V
-
82
-
dB
-
15
-
MHz
-
6
-
V/µs
-
±10
-
mA
V2_SD=VCC; ±10mA load on V2
-
±7
-
%
OSCILLATOR
Free Running Frequency
REFERENCES
Reference Voltage
(V2 Error Amp Reference)
VVREF
V1 Error Amp Reference Voltage
Tolerance
V1 Error Amp Reference
VREF
VCC=5
ERROR AMPLIFIERS
DC Gain
Gain-Bandwidth Product
GBW
Slew Rate
SR
COMP=10pF
WINDOW REGULATOR
Load Current
Output Voltage Error
GATE DRIVERS
Upper Gate Source (UGATE1 and 2)
IUGATE
VCC=5V, VUGATE=2.5V
-
-1
-
A
Upper Gate Sink (UGATE1 and 2)
IUGATE
VUGATE-PHASE=2.5V
-
1
-
A
Lower Gate Source (LGATE1 and 2)
ILGATE
VCC=5V, VLGATE=2.5V
-
-1
-
A
Lower Gate Sink (LGATE1 and 2)
ILGATE
VLGATE=2.5V
-
2
-
A
OCSET/SD Current Source
IOCSET
VOCSET=4.5VDC
34
40
46
µA
OCSET/SD Disable Voltage
VRESET
-
0.8
-
V
PROTECTION
5
ISL6531
Functional Pin Description
UGATE1
1
24 PGND1
BOOT1
2
23 LGATE1
BOOT1
UGATE1
UGATE1
PGND1
PGND1
LGATE1
PVCC1
32 LEAD 5X5 (QFN)
TOP VIEW
BOOT1
24 LEAD (SOIC)
TOP VIEW
22 PVCC1
32
31
30
29
28
27
26
25
PHASE1 3
21 OCSET/SD
VREF 4
24 PVCC1
VREF
2
23 OCSET/SD
FB1
3
22 V2_SD
COMP1
4
21 PGOOD
15 VCC
SENSE1
5
20 N/C
14 LGATE2
VREF_IN
6
19 SENSE2
GNDA
7
18 N/C
GNDA
8
17 VCC
19 PGOOD
6
18 N/C
SENSE1 7
17 SENSE2
VREF_IN 8
BOOT1 and BOOT2
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 NChannel MOSFET.
UGATE1 and UGATE2
9
10
11
12
13
14
15
16
PGND2
LGATE2
VCC
13 PGND2
PGND2
BOOT2 11
UGATE2 12
UGATE2
PHASE2 10
BOOT2
16 N/C
9
BOOT2
GNDA
1
PHASE2
COMP1
PHASE 1
20 V2_SD
FB1 5
(rDS(ON)) set the VDDQ converter overcurrent (OC) trip point
according to the following equation:
I OCS • R OCSET
I PEAK = ------------------------------------------r DS ( ON )
An overcurrent trip cycles the soft-start function.
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
of the VTT regulator has turned off.
LGATE1 and LGATE2
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 circuitry to determine when the
lower FET has turned off.
Pulling the OCSET/SD pin to ground resets the ISL6531 and
all external MOSFETS are turned off allowing the two output
voltage power rails to float.
PGOOD
A high level on this open-drain output indicates that both the
VDDQ and VTT regulators are within normal operating
voltage ranges.
GNDA
Signal ground for the IC. Tie this pin to the ground plane
through the lowest impedence connection available.
PGND1 and PGND2
VCC
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.
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.
OCSET/SD
V2_SD
A resistor (ROCSET) connected from this pin to the drain of
the upper MOSFET of the VDDQ regulator sets the
overcurrent trip point. ROCSET, an internal 40µA current
source (IOCS), and the upper MOSFET on-resistance
A high level on the V2_SD input places the VTT controller
into “sleep” mode. In sleep mode, both UGATE2 and
LGATE2 are driven low, effectively floating the VTT supply.
6
ISL6531
While the VTT supply “floats”, it is held to about 50% of
VDDQ via a low current window regulator which drives VTT
via the SENSE2 pin. The window regulator can overcome up
to at least ±10mA of leakage on VTT.
While V2_SD is high, PGOOD is low.
PHASE1 and PHASE2
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 VDDQ
regulator for overcurrent protection. The PHASE1 pin is
monitored by the adaptive shoot through protection circuitry
to determine when the upper FET of the VDDQ supply has
turned off.
FB1, COMP1
COMP1 and FB1 are the available external pins of the error
amplifier for the VDDQ regulator. The FB1 pin is the inverting
inputs of the error amplifier and the COMP1 pin is the
associated output. An appropriate AC network across these
pins is used to compensate the voltage-controlled feedback
loop of the VDDQ converter.
VREF and VREF_IN
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
voltage is used as the reference input of the VTT error
amplifier. Thus VTT is controlled to 50% of VDDQ.
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 VTT supply. A
100pF capacitor between VREF_IN and ground is
recommended for proper operation.
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 VDDQ and VTT supplies,
respectively. SENSE1 is used as an input to create the
voltage at VREF_OUT and the reference voltage for the VTT
supply. SENSE2 is used as the feedback pin of the VTT
regulator and as the regulation point for the window regulator
that is enabled in V2_SD mode.
Functional Description
Overview
The ISL6531 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
7
300kHz clocks. The clocks are phase locked and displaced
90o to minimize noise coupling between the controllers.
The first regulator includes a precision 0.8V reference and is
intended to provide the proper VDDQ to a DDRAM memory
system. The VDDQ controller implements overcurrent
protection utilizing the rDS(ON) of the upper MOSFET.
Following a fault condition, the VDDQ regulator is softstarted
via a digital soft-start circuit.
Included in the ISL6531 is a precision VREF reference
output. VREF is a buffered representation of 1--- ⋅ V DDQ . VREF
2
is derived via a precision internal resistor divider connected
to the SENSE1 terminal.
The second PWM regulator is designed to provide VTT
termination for the DDRAM signal lines. The reference to the
VTT regulator is VREF. Thus the VTT regulator provides a
termination voltage equal to 1--- ⋅ V DDQ . The drain of the
2
upper MOSFET of the VTT supply is connected to the
regulated VDDQ voltage. The VTT controller is designed to
enable both sinking and sourcing current on the VTT rail.
Two benefits result from the ISL6531 dual controller
topology. First, as VREF is always 1--- ⋅ V DDQ , the VTT supply
2
will track the VDDQ supply during soft-start cycles. Second,
the overcurrent protection incorporated into the VDDQ supply
will simultaneously protect the VTT supply.
Initialization
The ISL6531 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.
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.
With the VTT regulator reference held at 1--- ⋅ V DDQ it will
2
automatically track the ramp of the VDDQ softstart, thus
enabling a soft-start for VTT.
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.
ISL6531
VCC (5V)
(1V/DIV)
VDDQ (2.5V)
VTT (1.25V)
0V
T0
T1
T2
TIME
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 ISL6531
incorporates specialized circuitry which insures that
complementary MOSFETs are not ON simultaneously.
The adaptive shoot-through protection utilized by the VDDQ
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
shoot-through protection allows the VDDQ regulator to
source current only.
Due to the necessity of sinking current, the VTT regulator
employs a modified protection scheme from that of the
VDDQ regulator. If the voltage from UGATE2 or from
LGATE2 to GND is less than 0.8V, then the respective
MOSFET is defined as being OFF and the other MOSFET is
turned ON.
Since the voltage of the lower MOSFET gates and the upper
MOSFET gate of the VTT supply 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 shootthrough protection.
When the V2_SD input of the ISL6531 is driven high, the
VTT regulator is placed into a “sleep” state. In the sleep state
the main VTT regulator is disabled, with both the upper and
lower MOSFETs being turned off. The VTT bus is maintained
at close to 1--- ⋅ V DDQ via a low current window regulator
2
which drives VTT via the SENSE2 pin. Maintaining VTT at
1
--- ⋅ V DDQ consumes negligible power and enables rapid
2
wake-up from sleep mode without the need of softstarting
the VTT regulator. During this power down mode, PGOOD is
held LOW.
Output Voltage Selection
The output voltage of the VDDQ regulator can be
programmed to any level between VIN (i.e. +5V) and the
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.F 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 5kΩ. R4 can be
calculated based on the following equation:
R1 × 0.8V
R4 = -------------------------------------V OUT1 – 0.8V
If the output voltage desired is 0.8V, simply route VDDQ back
to the FB pin through R1, but do not populate R4.
+5V
D1
VCC
BOOT1
C4
UGATE1
ISL6531
Q1
LOUT1
VDDQ
PHASE1
Q2
LGATE1
+
COUT1
FB1
C1
COMP1
R1
C3
C2
R3
R2
R4
FIGURE 3. OUTPUT VOLTAGE SELECTION OF VDDQ
Power Down Mode
VTT Reference Overdrive
DDRAM systems include a sleep state in which the VDDQ
voltage to the memories is maintained, but signaling is
suspended. During this mode the VTT termination voltage is
no longer needed. The only load placed on the VTT bus is
the leakage of the associated signal pins of the DDRAM and
memory controller ICs.
The ISL6531 allows the designer to bypass the internal 50%
tracking of VDDQ that is used as the reference for VTT. The
ISL6531 was designed to divide down the VDDQ voltage by
50% through two internal matched resistances. These
resistances are typically 200kΩ.
8
ISL6531
One method that may be employed to bypass the internal
VTT reference generation is to supply an external reference
directly to the VREF_IN pin. When doing this the SENSE1
pin must remain unconnected. Caution must be exercised
when using this method as the VTT regulator does not
employ a soft start of its own.
programs the overcurrent trip level (see Figure 1). An internal
40µA (typical) current sink develops a voltage across ROCSET
that is referenced to VIN. When the voltage across the upper
MOSFET of VDDQ (also referenced to VIN) exceeds the
voltage across ROCSET , the overcurrent function initiates a
soft-start sequence.
A second method would be to overdrive the internal
resistors. Figure 3 shows how to implement this method. The
external resistors used to overdrive the internal resistors
should be less than 2kΩ and have a tolerance of 1% or
better. This method still supplies a buffer between the
resistor network and any loading on the VREF pin. If there is
no loading on the VREF pin, then no buffering is necessary
and the reference voltage created by the resistor network
can be tied directly to VREF.
Figure 5 illustrates the protection feature responding to an
overcurrent event on VDDQ. At time t0, an overcurrent
condition is sensed across the upper MOSFET of the VDDQ
regulator. As a result, both regulators are quickly shutdown
and the internal soft-start function begins producing softstart ramps. The delay interval seen by the output is
equivalent to three soft-start cycles. The fourth internal softstart 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.
VDDQ
ISL6531
SENSE1
VREF_IN
RA
VREF
+
-
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.
RB
VDDQ (2.5V)
TO ERROR
AMPLIFIER
VTT (1.25V)
FIGURE 4. VTT REFERENCE OVERDRIVE
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
Voltage Monitoring
DELAY INTERVAL
The ISL6531 offers a PGOOD signal that will communicate
whether the regulation of both VDDQ and VTT are within
±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.
Overcurrent Protection
The overcurrent function protects the converter from a shorted
output by using the upper MOSFET on-resistance, rDS(ON), of
VDDQ to monitor the current. This method enhances the
converter’s efficiency and reduces cost by eliminating a
current sensing resistor.
The overcurrent function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (ROCSET)
9
T1
T0
T2
TIME
FIGURE 5. OVERCURRENT PROTECTION RESPONSE
The overcurrent function will trip at a peak inductor current
(IPEAK) determined by:
I OCSET x R OCSET
I PEAK = ---------------------------------------------------r DS ( ON )
where IOCSET is the internal OCSET current source (40µA
typical). The OC trip point varies mainly due to the MOSFET
rDS(ON) variations. To avoid overcurrent tripping in the
ISL6531
normal operating load range, find the ROCSET resistor from
the equation above with:
1. The maximum rDS(ON) at the highest junction
temperature.
2. The minimum IOCSET from the specification table.
3. Determine IPEAK for
( ∆I -)
I PEAK > I OUT ( MAX ) + --------,
2
+5V
ISL6531
UGATE1
PHASE1
VDDQ
LGATE1
DDR
SDRAM
where ∆I is the output inductor ripple current.
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
ROCSET to smooth the voltage across ROCSET in the
presence of switching noise on the input voltage.
Current Sinking
The ISL6531 VTT regulator incorporates a MOSFET shootthrough protection method which allows the converter to sink
current as well as source current. Care should be exercised
when designing a converter with the ISL6531 when it is
known that the converter may sink current.
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 the allow 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.
To insure that the current does not boost up the input rail
voltage of the VTT regulator, it is recommended that the
input rail of the VTT regulator be the output of the VDDQ
regulator. The current being sunk by the VTT regulator will
be fed into the VDDQ rail and then drawn into the DDR
SDRAM memory module and back into the VTT regulator.
Figure 6 shows the recommended configuration and the
resulting current loop.
UGATE2
PHASE2
VTT
LGATE2
+
-
RT
VREF
FIGURE 6. VTT CURRENT SINKING LOOP
Application Guidelines
Layout Considerations
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 over-voltage stress. Careful component
layout and printed circuit board design minimizes the voltage
spikes in the converters.
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.
There are two sets of critical components in a DC-DC
converter using the ISL6531. The switching components are
the most critical because they switch large amounts o
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.
A multi-layer printed circuit board is recommended. Figure 7
shows the connections of the critical components in the
converter. Note that capacitors CIN and COUT could each
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
10
ISL6531
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.f
+5V VIN
ISL6531
VCC
CBP
GND
VDDQ Feedback Compensation
CIN
D1
BOOT1
CBOOT1
Q1
UGATE1
LOUT1
PHASE1
VDDQ
Q2
LOAD
PHASE1
COUT1
LGATE1
PGND1
C2A
C1A
R1A
FB1
C3A R3A
R4
This section discusses the feedback compensation of the
VDDQ regulator. Figure 8 highlights the voltage-mode
control loop for a synchronous-rectified buck converter. The
output voltage (VOUT) is regulated to the Reference voltage
level. The error amplifier (error amp) output (VE/A) is
compared with the oscillator (OSC) triangular wave to
provide a pulse-width modulated (PWM) wave with an
amplitude of VIN at the PHASE node. The PWM wave is
smoothed by the output filter (LO and CO).
The modulator transfer function is the small-signal transfer
function of VOUT/VE/A . This function is dominated by a DC
gain and the output filter (LO and CO), with a double pole
break frequency at FLC and a zero at FESR . The DC gain of
the modulator is simply the input voltage (VIN) divided by the
peak-to-peak oscillator voltage ∆VOSC .
COMP1
R2A
The critical small signal components include any bypass
capacitors, feedback components, and compensation
components. Position the bypass capacitor, CBP, close to the
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.
SENSE1
VIN
DRIVER
OSC
PWM
COMPARATOR
+5V VIN
D2
DVOSC
VDDQ
BOOT2
LO
DRIVER
+
VOUT
PHASE C
O
CBOOT2
ESR
(PARASITIC)
Q3
UGATE2
LOUT2
PHASE2
VTT
Q4
LGATE2
COUT2
LOAD
PHASE2
PGND2
ZFB
VE/A
+
ZIN
REFERENCE
ERROR
AMP
DETAILED COMPENSATION COMPONENTS
SENSE2
ZFB
C1
KEY
C2
ISLAND ON POWER PLANE LAYER
VOUT
ZIN
C3
R2
R3
ISLAND ON CIRCUIT PLANE LAYER
VIA CONNECTION TO GROUND PLANE
11
FB
+
FIGURE 7. PRINTED CIRCUIT BOARD POWER PLANES
AND ISLANDS
The switching components should be placed close to the
ISL6531 first. Minimize the length of the connections
between the input capacitors, CIN, and the power switches
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.
R1
COMP
ISL6531
REFERENCE
FIGURE 8. VOLTAGE-MODE BUCK CONVERTER
COMPENSATION DESIGN
Modulator Break Frequency Equations
1
F LC = ----------------------------------------2π x L O x C O
1
F ESR = -----------------------------------------2π x ESR x C O
ISL6531
The compensation network consists of the error amplifier
(internal to the ISL6531) and the impedance networks ZIN
and ZFB. The goal of the compensation network is to provide
a closed loop transfer function with the highest 0dB crossing
frequency (f0dB) and adequate phase margin. Phase margin
is the difference between the closed loop phase at f0dB and
180 degrees. The equations below relate the compensation
network’s poles, zeros and gain to the components (R1 , R2 ,
R3 , C1 , C2 , and C3) in Figure 7. Use these guidelines for
locating the poles and zeros of the compensation network:
1. Pick gain (R2/R1) for desired converter bandwidth.
2. Place first zero below filter’s double pole (~75% FLC).
3. Place second zero at filter’s double pole.
4. Place first pole at the ESR zero.
5. Place second pole at half the switching frequency.
The compensation gain uses external impedance networks
ZFB and ZIN to provide a stable, high bandwidth (BW) overall
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
VTT Feedback Compensation
To ease design and reduce the number of small-signal
components required, the VTT regulator is internally
compensated. The only stability criteria that needs to be
met relates the minimum value of the inductor to the
equivalent ESR of the output capacitor bank as shown in
the following equation:
L OUT ( MIN ) ≥ 20 ⋅ ( 10
–6
) × ESR OUT × V IN
6. Check gain against error amplifier’s open-loop gain.
7. Estimate phase margin - repeat if necessary.
Compensation Break Frequency Equations
1
F Z1 = --------------------------------2π × R 2 × C 2
1
F P1 = -------------------------------------------------------- C 1 x C 2
2π x R 2 x  ----------------------
 C1 + C2 
1
F Z2 = ------------------------------------------------------2π x ( R 1 + R 3 ) x C 3
1
F P2 = -----------------------------------2π x R 3 x C 3
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 compensation gain at FP2 with the capabilities of
the error 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..
FZ1
FZ2
FP1
FP2
100
OPEN LOOP
ERROR AMP GAIN
 V IN 
20 log  ----------------
 V OSC
80
GAIN (dB)
60
40
COMPENSATION
GAIN
20
0
-20
-40
-60
R2
20 log  --------
 R1
MODULATOR
GAIN
10
100
FLC
1K
LOOP GAIN
FESR
10K
100K
1M
10M
FREQUENCY (Hz)
FIGURE 9. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
12
where
LOUT(MIN) = minimum output inductor value at full output
current
ESROUT = equivalent ESR of the output capacitor bank
VIN = Input voltage of the converter
The design procedure for this output should follow the
following steps:
1. Choose the number and type of output capacitors to meet
the output transient requirements based on the dynamic
loading characteristics of the output.
2. Determine the equivalent ESR of the output capacitor
bank and calculate the minimum output inductor value.
3. Verify that the chosen inductor meets this minimum value
criteria at full output load. It is recommended that the
chosen inductor be no more than 30% saturated at full
output load.
Component Selection Guidelines
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.
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.
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
ISL6531
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load on
specific decoupling requirements.
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.
Output Inductor Selection
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. Additionally, the output inductor for
the VTT regulator has to meet the minimum value criteria for
loop stability as described in the VTT Feedback
Compensation section. 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:
∆I =
VIN - VOUT
fs x L
x
VOUT
VIN
∆VOUT = ∆I x ESR
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
ISL6531 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.
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:
tRISE =
L x ITRAN
VIN - VOUT
tFALL =
L x ITRAN
VOUT
where: ITRAN is the transient load current step, tRISE is the
response time to the application of load, and tFALL is the
13
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
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 Q1 turns on. Place the
small ceramic capacitors physically close to the MOSFETs
and between the drain of Q1 and the source of Q2 .
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
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
The maximum RMS current required by the regulator may be
closely approximated through the following equation:
I RMS
MAX
=
2
V OUT 
2
1  V IN – V OUT V OUT 
---------------- ×  I OUT
+ ------ ×  -------------------------------- × ---------------- 
L × fs
V IN
V IN  
12 
MAX

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.
MOSFET Selection/Considerations
The ISL6531 requires two N-Channel power MOSFETs for
each PWM regulator. These should be selected based upon
rDS(ON) , gate supply requirements, and thermal 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 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. The VDDQ
regulator will only source current while the VTT regulator can
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
ISL6531
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 ISL6531 and don't heat the MOSFETs. However, large
gate-charge increases the switching interval, tSW which
increases the MOSFET switching losses.
LOSSES WHILE SOURCING CURRENT
2
1
P UPPER = Io × r DS ( ON ) × D + --- ⋅ Io × V IN × t SW × f s
2
PLOWER = Io2 x rDS(ON) x (1 - D)
VCC
DBOOT
Where: D is the duty cycle = VOUT / VIN ,
tSW is the combined switch ON and OFF time, and
fs is the switching frequency.
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 heat sink may be necessary
depending upon MOSFET power, package type, ambient
temperature and air flow.
Given the reduced available gate bias voltage (5V), logiclevel or sub-logic-level transistors should be used for both NMOSFETs. Caution should be exercised when using devices
with very low gate thresholds (VTH). The shoot-through
protection circuitry may be circumvented by these
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.
Bootstrap Component Selection
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
boot capacitor, CBOOT, develops a floating supply voltage
referenced to the PHASE pin. This supply is refreshed each
cycle, when DBOOT conducts, to a voltage of VCC less the
boot diode drop, VD, plus the voltage rise across QLOWER.
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 GATE = C BOOT × ( V BOOT1 – V BOOT2 )
14
VIN
BOOTn
CBOOT
ISL6531
UGATEn
QUPPER
PHASEn
+
LGATEn
NOTE:
VG-S ≈ VCC -VD
QLOWER
NOTE:
VG-S ≈ VCC
LOSSES WHILE SINKING CURRENT
PUPPER = Io2 x rDS(ON) x D
2
1
P LOWER = Io × r DS ( ON ) × ( 1 – D ) + --- ⋅ Io × V IN × t SW × f s
2
+
VD
-
GND
FIGURE 10. UPPER GATE DRIVE BOOTSTRAP
where QGATE is the maximum total gate charge of the upper
MOSFET, CBOOT is the bootstrap capacitance, VBOOT1 is
the bootstrap voltage immediately before turn-on, and
VBOOT2 is the bootstrap voltage immediately after turn-on.
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
rearranging the previous equation and solving for CBOOT.
Q GATE
C BOOT ≥ ----------------------------------------------------V BOOT1 – V
BOOT2
Typical gate charge values for MOSFETs considered in
these types of applications range from 20 to 100nC. Since
the voltage drop across QLOWER is negligible, VBOOT1 is
simply VCC - VD. A schottky diode is recommended to
minimize the voltage drop across the bootstrap capacitor
during the on-time of the upper MOSFET. Initial calculations
with VBOOT2 no less than 4V will quickly help narrow the
bootstrap capacitor range.
For example, consider an upper MOSFET is chosen with a
maximum gate charge, Qg, 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.
A fast recovery diode is recommended when selecting a
bootstrap diode to reduce the impact of reverse recovery
charge loss. Otherwise, the recovery charge, QRR, would
have to be added to the gate charge of the MOSFET and
taken into consideration when calculating the minimum
bootstrap capacitance.
ISL6531
ISL6531 DC-DC Converter Application Circuit
inApplication Note AN9993-of-Materials and circuit board
description, can be found in Application Note AN9993
Application Note AN9993-of-Materials and circuit board
description, can be found in Application Note AN9993.
Figure 11 shows an application circuit for a DDR SDRAM
power supply, including VDDQ (+2.5V) and VTT (+1.25V).
Detailed information on the circuit, including a complete
Billof-Materials and circuit board description, can be found
+5V
R1
3.48kΩ
C2
0.1µF
C1
1000pF
OCSET/SD
D1
C3
1.0µF
VCC
C4,5
150µF(x2)
BOOT1
V2_SD
PGOOD
Q1
UGATE1
VREF
C6
0.1µF
PHASE1
VREF_IN
L1
1µH
PVCC1
C30
100pF
C7,8,9,10
150µF(x4)
Q2
LGATE1
GNDA
VDDQ
@10A
C15
0.1µF
PGND1
ISL6531
D2
C26
5600pF
COMP1
R26
6.34kΩ
BOOT2
C27
100pF
C17
1.0µF
UGATE2
C16
0.1µF
PHASE2
R20
L2
1µH
LGATE2
FB1
1.43kΩ
VTT
@5A
C18,19
Q3
150µF(x2)
PGND2
SENSE1
SENSE2
R19
3.01kΩ
C25
15000pF
R25
100Ω
Component Selection Notes:
C4,5,7,8,9,10,18,19 - Each 150mF, Panasonic EEF-UE0J151R
D1,2 - Each 30mA Schottky Diode, MA732
L1,2 - Each 1mH Inductor, Panasonic P/N ETQ-P6F1ROSFA
Q1,2 - Each Fairchild MOSFET; ITF86130DK8
Q3 - Fairchild MOSFET; ITF86110DK8
FIGURE 11. DDR SDRAM VOLTAGE REGULATOR
15
ISL6531
Small Outline Plastic Packages (SOIC)
M24.3 (JEDEC MS-013-AD ISSUE C)
24 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE
INCHES
N
INDEX
AREA
0.25(0.010) M
H
SYMBOL
B M
E
-B1
2
3
L
SEATING PLANE
-A-
h x 45o
A
D
-C-
A1
B
0.25(0.010) M
C
0.10(0.004)
C A M
B S
MAX
MILLIMETERS
MIN
MAX
NOTES
A
0.0926
0.1043
2.35
2.65
-
A1
0.0040
0.0118
0.10
0.30
-
B
0.013
0.020
0.33
0.51
9
C
0.0091
0.0125
0.23
0.32
-
D
0.5985
0.6141
15.20
15.60
3
E
0.2914
0.2992
7.40
7.60
4
e
µα
e
MIN
0.05 BSC
1.27 BSC
-
H
0.394
0.419
10.00
10.65
-
h
0.010
0.029
0.25
0.75
5
L
0.016
0.050
0.40
1.27
6
8o
0o
N
α
24
0o
24
7
8o
Rev. 0 12/93
NOTES:
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
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. Interlead 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.
16
ISL6531
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
NOTES
A
0.80
0.90
1.00
-
A1
-
-
0.05
-
A2
-
-
1.00
9
A3
b
0.20 REF
0.18
D
0.30
5,8
5.00 BSC
D1
D2
0.23
9
-
4.75 BSC
2.95
3.10
9
3.25
7,8
E
5.00 BSC
-
E1
4.75 BSC
9
E2
2.95
e
3.10
3.25
7,8
0.50 BSC
-
k
0.25
-
-
-
L
0.30
0.40
0.50
8
L1
-
-
0.15
10
N
Nd
32
2
8
3
Ne
8
8
3
P
-
-
0.60
9
θ
-
-
12
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 dimensions are provided to assist with PCB Land Pattern
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
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