DATASHEET

PX3511A, PX3511B
®
Data Sheet
February 26, 2007
Advanced Synchronous Rectified Buck
MOSFET Drivers with Protection Features
The PX3511A and PX3511B are high frequency MOSFET
drivers specifically designed to drive upper and lower power
N-Channel MOSFETs in a synchronous rectified buck
converter topology. These drivers combined with the
ISL6595 Digital Multi-Phase Buck PWM controller and
N-Channel MOSFETs form a complete core-voltage
regulator solution for advanced microprocessors.
The PX3511A drives the upper gate to 12V, while the lower
gate can be independently driven over a range from 5V to
12V. The PX3511B drives both upper and lower gates over a
range of 5V to 12V. This drive-voltage provides the flexibility
necessary to optimize applications involving trade-offs
between gate charge and conduction losses.
An adaptive zero shoot-through protection is integrated to
prevent both the upper and lower MOSFETs from conducting
simultaneously and to minimize the dead time. These
products add an overvoltage protection feature operational
before VCC exceeds its turn-on threshold, at which the
PHASE node is connected to the gate of the low side
MOSFET (LGATE). The output voltage of the converter is
then limited by the threshold of the low side MOSFET, which
provides some protection to the microprocessor if the upper
MOSFET(s) is shorted during initial start-up.
These drivers also feature a three-state PWM input which,
working together with Intersil’s multi-phase PWM controllers,
prevents a negative transient on the output voltage when the
output is shut down. This feature eliminates the Schottky
diode that is used in some systems for protecting the load
from reversed output voltage events.
FN6462.0
Features
• Dual MOSFET Drives for Synchronous Rectified Bridge
• Adjustable Gate Voltage (5V to 12V) for Optimal Efficiency
• 36V Internal Bootstrap Schottky Diode
• Bootstrap Capacitor Overcharging Prevention
• Supports High Switching Frequency (up to 2MHz)
- 3A Sinking Current Capability
- Fast Rise/Fall Times and Low Propagation Delays
• Three-State PWM Input for Output Stage Shutdown
• Three-State PWM Input Hysteresis for Applications With
Power Sequencing Requirement
• Pre-POR Overvoltage Protection
• VCC Undervoltage Protection
• Expandable Bottom Copper Pad for Enhanced Heat
Sinking
• Dual Flat No-Lead (DFN) Package
- Near Chip-Scale Package Footprint; Improves PCB
Efficiency and Thinner in Profile
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• Core Regulators for Intel® and AMD® Microprocessors
• High Current DC/DC Converters
• High Frequency and High Efficiency VRM and VRD
Related Literature
• Technical Brief TB363 “Guidelines for Handling and
Processing Moisture Sensitive Surface Mount Devices
(SMDs)”
• Technical Brief TB417 for Power Train Design, Layout
Guidelines, and Feedback Compensation Design
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
PX3511A, PX3511B
Ordering Information
PART NUMBER
PART MARKING
TEMP. RANGE (°C)
PACKAGE
PKG. DWG. #
PX3511ADAG (Note)
PX3511 ADAG
0 to +85
8 Ld SOIC (Pb-free)
M8.15
PX3511ADAG-R3 (Note)
PX3511 ADAG
0 to +85
8 Ld SOIC (Pb-free) Tape and Reel
M8.15
PX3511ADDG
11AD
0 to +85
10 Ld 3x3 DFN
L10.3x3
PX3511ADDG-RA
11AD
0 to +85
10 Ld 3x3 DFN Tape and Reel
L10.3x3
PX3511BDAG (Note)
PX351 BDAG
0 to +85
8 Ld SOIC (Pb-free)
M8.15
PX3511BDAG-R3 (Note)
PX3511 BDAG
0 to +85
8 Ld SOIC (Pb-free) Tape and Reel
M8.15
PX3511BDDG
11BD
0 to +85
10 Ld 3x3 DFN
L10.3x3
PX3511BDDG-RA
11BD
0 to +85
10 Ld 3x3 DFN Tape and Reel
L10.3x3
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.
Pinouts
PX3511ACR, PX3511BCR
(10 LD 3x3 DFN)
TOP VIEW
PX3511ACB, PX3511BCB
(8 LD SOIC)
TOP VIEW
UGATE
1
8
PHASE
BOOT
2
7
PVCC
PWM
3
6
VCC
4
GND
5
LGATE
CRD L
UGATE
1
10
BAT
PHASE
BOOT
USB
2
9
PVCC
ICDL
N/C
PPR
3
8
GND
N/C
PW
M
C HG
4
7
VCC
USBP
NTC orGND
OVP
5
6
IUSB
LGATE
or EN
Block Diagram
PX3511A AND PX3511B
UVCC
BOOT
VCC
UGATE
Pre-POR OVP
FEATURES
+5V
10K
POR/
PWM
SHOOTTHROUGH
PROTECTION
PHASE
(LVCC)
PVCC
UVCC = VCC FOR PX3511A
UVCC = PVCC FOR PX3511B
CONTROL
8K
LOGIC
LGATE
GND
PAD
2
FOR DFN -DEVICES, THE PAD ON THE BOTTOM SIDE OF
THE PACKAGE MUST BE SOLDERED TO THE CIRCUIT’S GROUND.
FN6462.0
February 26, 2007
Typical Application - 4 Channel Converter Using ISL6595 and PX3511A Gate Drivers
+12V
PX3511
+5V
1 UGATE
PHASE 8
2 BOOT
PVCC 7
3 PWM
VCC 6
4 GND
LGATE 5
3
+3.3V
VDD
V12_SEN
PHASE 8
OUT1
2 BOOT
PVCC 7
VID4
OUT2
3 PWM
VCC 6
VID3
ISEN1
4 GND
LGATE 5
VID2
OUT3
VID1
OUT4
VID0
ISEN2
VID5
OUT5
LL0
OUT6
LL1
ISEN3
OUTEN
OUT7
OUT8
TO µP
VCC_PWRGD
Vout
PX3511
1 UGATE
PHASE 8
2 BOOT
PVCC 7
3 PWM
VCC 6
4 GND
LGATE 5
RTN
ISEN4
OUT9
RESET_N
OUT10
PX3511
ISEN5
1 UGATE
PHASE 8
PVCC 7
FAULT
FAULT1
OUT11
2 BOOT
OUTPUTS
FAULT2
OUT12
3 PWM
VCC 6
ISEN6
4 GND
LGATE 5
FN6462.0
February 26, 2007
I2C I/F
BUS
SDA
TEMP_SEN
SCL
CAL_CUR_EN
RTHERM
SADDR
CAL_CUR_SEN
VSENP
VSENN
PX3511A, PX3511B
1 UGATE
ISL6595
FROM µP
PX3511
GND
PX3511A, PX3511B
Absolute Maximum Ratings
Thermal Information
Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15V
Supply Voltage (PVCC) . . . . . . . . . . . . . . . . . . . . . . . . . VCC + 0.3V
BOOT Voltage (VBOOT). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36V
Input Voltage (VPWM) . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to 7V
UGATE. . . . . . . . . . . . . . . . . . . VPHASE - 0.3VDC to VBOOT + 0.3V
VPHASE - 3.5V (<100ns Pulse Width, 2µJ) to VBOOT + 0.3V
LGATE . . . . . . . . . . . . . . . . . . . . . . GND - 0.3VDC to VPVCC + 0.3V
GND - 5V (<100ns Pulse Width, 2µJ) to VPVCC + 0.3V
PHASE. . . . . . . . . . . . . . . GND - 0.3VDC to 15VDC (VPVCC = 12V)
Thermal Resistance
θJA (°C/W)
θJC (°C/W)
SOIC Package (Note 1) . . . . . . . . . . . .
100
N/A
DFN Package (Notes 2, 3) . . . . . . . . . .
48
7
Maximum Junction Temperature (Plastic Package) . . . . . . . +150°C
Maximum Storage Temperature Range . . . . . . . . . .-65°C to +150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . +300°C
(SOIC - Lead Tips Only)
GND - 8V (<400ns, 20µJ) to 30V (<200ns, VBOOT-GND<36V)
ESD Rating
Human Body Model . . . . . . . . . . . . . . . . . . . . Class I JEDEC STD
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . 0°C to +85°C
Maximum Operating Junction Temperature . . . . . . . . . . . . . +125°C
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12V ±10%
Supply Voltage Range, PVCC . . . . . . . . . . . . . . . . 5V to 12V ±10%
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. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air.
2. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
3. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
Electrical Specifications
Recommended Operating Conditions, Unless Otherwise Noted.
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
IVCC
PX3511A, fPWM = 300kHz, VVCC = 12V
-
8
-
mA
PX3511B, fPWM = 300kHz, VVCC = 12V
-
4.5
-
mA
PX3511A, fPWM = 1MHz, VVCC = 12V
-
10.5
-
mA
PX3511B, fPWM = 1MHz, VVCC = 12V
-
5
-
mA
PX3511A, fPWM = 300kHz, VPVCC = 12V
-
4
-
mA
PX3511B, fPWM = 300kHz, VPVCC = 12V
-
7.5
-
mA
PX3511A, fPWM = 1MHz, VPVCC = 12V
-
5
-
mA
PX3511B, fPWM = 1MHz, VPVCC = 12V
-
8.5
-
mA
VCC Rising Threshold
9.35
9.8
10.0
V
VCC Falling Threshold
7.35
7.6
8.0
V
-
505
-
µA
VCC SUPPLY CURRENT
Bias Supply Current
IVCC
Gate Drive Bias Current
IPVCC
IPVCC
(Note 4)
POWER-ON RESET AND ENABLE
PWM INPUT (See Timing Diagram on Page 6)
Input Current
IPWM
VPWM = 3.3V
VPWM = 0V
-
-460
-
µA
PWM Rising Threshold (Note 4)
VCC = 12V
-
1.70
-
V
PWM Falling Threshold (Note 4)
VCC = 12V
-
1.30
-
V
Typical Three-State Shutdown Window
VCC = 12V
1.23
-
1.82
V
Three-State Lower Gate Falling Threshold
VCC = 12V
-
1.18
-
V
Three-State Lower Gate Rising Threshold
VCC = 12V
-
0.76
-
V
Three-State Upper Gate Rising Threshold
VCC = 12V
-
2.36
-
V
4
FN6462.0
February 26, 2007
PX3511A, PX3511B
Electrical Specifications
Recommended Operating Conditions, Unless Otherwise Noted. (Continued)
PARAMETER
SYMBOL
Three-State Upper Gate Falling Threshold
Shutdown Holdoff Time
TEST CONDITIONS
VCC = 12V
tTSSHD
MIN
TYP
MAX
UNITS
-
1.96
-
V
-
245
-
ns
UGATE Rise Time
tRU
VPVCC = 12V, 3nF Load, 10% to 90%
-
26
-
ns
LGATE Rise Time
tRL
VPVCC = 12V, 3nF Load, 10% to 90%
-
18
-
ns
UGATE Fall Time (Note 4)
tFU
VPVCC = 12V, 3nF Load, 90% to 10%
-
18
-
ns
LGATE Fall Time (Note 4)
tFL
VPVCC = 12V, 3nF Load, 90% to 10%
-
12
-
ns
UGATE Turn-On Propagation Delay (Note 4)
tPDHU
VPVCC = 12V, 3nF Load, Adaptive
-
10
-
ns
LGATE Turn-On Propagation Delay (Note 4)
tPDHL
VPVCC = 12V, 3nF Load, Adaptive
-
10
-
ns
UGATE Turn-Off Propagation Delay (Note 4)
tPDLU
VPVCC = 12V, 3nF Load
-
10
-
ns
LGATE Turn-Off Propagation Delay (Note 4)
tPDLL
VPVCC = 12V, 3nF Load
-
10
-
ns
LG/UG Three-State Propagation Delay (Note 4)
tPDTS
VPVCC = 12V, 3nF Load
-
10
-
ns
Upper Drive Source Current (Note 4)
IU_SOURCE VPVCC = 12V, 3nF Load
-
1.25
-
A
Upper Drive Source Impedance
RU_SOURCE 150mA Source Current
1.4
2.0
3.0
Ω
-
2
-
A
0.9
1.65
3.0
Ω
-
2
-
A
0.85
1.3
2.2
Ω
-
3
-
A
0.60
0.94
1.35
Ω
OUTPUT
Upper Drive Sink Current (Note 4)
IU_SINK
VPVCC = 12V, 3nF Load
Upper Drive Sink Impedance
RU_SINK
150mA Sink Current
Lower Drive Source Current (Note 4)
IL_SOURCE
Lower Drive Source Impedance
RL_SOURCE 150mA Source Current
VPVCC = 12V, 3nF Load
Lower Drive Sink Current (Note 4)
IL_SINK
VPVCC = 12V, 3nF Load
Lower Drive Sink Impedance
RL_SINK
150mA Sink Current
NOTE:
4. Guaranteed by design. Not 100% tested in production.
Functional Pin Description
PACKAGE PIN #
SOIC
DFN
PIN
SYMBOL
1
1
UGATE
Upper gate drive output. Connect to gate of high-side power N-Channel MOSFET.
2
2
BOOT
Floating bootstrap supply pin for the upper gate drive. Connect the bootstrap capacitor between this pin and the
PHASE pin. The bootstrap capacitor provides the charge to turn on the upper MOSFET. See the Internal Bootstrap
Device section under DESCRIPTION for guidance in choosing the capacitor value.
-
3,8
N/C
3
4
PWM
The PWM signal is the control input for the driver. The PWM signal can enter three distinct states during operation, see
the three-state PWM Input section under DESCRIPTION for further details. Connect this pin to the PWM output of the
controller.
4
5
GND
Bias and reference ground. All signals are referenced to this node. It is also the power ground return of the driver.
5
6
LGATE
6
7
VCC
7
9
PVCC
This pin supplies power to both upper and lower gate drives in PX3511B; only the lower gate drive in PX3511A.
Its operating range is +5V to 12V. Place a high quality low ESR ceramic capacitor from this pin to GND.
8
10
PHASE
Connect this pin to the SOURCE of the upper MOSFET and the DRAIN of the lower MOSFET. This pin provides
a return path for the upper gate drive.
9
11
PAD
FUNCTION
No Connection.
Lower gate drive output. Connect to gate of the low-side power N-Channel MOSFET.
Connect this pin to a +12V bias supply. Place a high quality low ESR ceramic capacitor from this pin to GND.
Connect this pad to the power ground plane (GND) via thermally enhanced connection.
5
FN6462.0
February 26, 2007
PX3511A, PX3511B
Description
1.18V<PWM<2.36V
0.76V<PWM<1.96V
PWM
tPDLU
tPDHU
tTSSHD
tPDTS
tPDTS
UGATE
tFU
tRU
LGATE
tFL
tRL
tTSSHD
tPDLL
tPDHL
FIGURE 1. TIMING DIAGRAM
Operation
Adaptive Zero Shoot-Through Deadtime Control
Designed for versatility and speed, the PX3511A and
PX3511B MOSFET drivers control both high-side and lowside N-Channel FETs of a half-bridge power train from one
externally provided PWM signal.
These drivers incorporate an adaptive deadtime control
technique to minimize deadtime, resulting in high efficiency
from the reduced freewheeling time of the lower MOSFETs’
body-diode conduction, and to prevent the upper and lower
MOSFETs from conducting simultaneously. This is
accomplished by ensuring either rising gate turns on its
MOSFET with minimum and sufficient delay after the other
has turned off.
Prior to VCC exceeding its POR level, the Pre-POR
overvoltage protection function is activated during initial
startup; the upper gate (UGATE) is held low and the lower
gate (LGATE), controlled by the Pre-POR overvoltage
protection circuits, is connected to the PHASE. Once the
VCC voltage surpasses the VCC Rising Threshold (See
Electrical Specifications), the PWM signal takes control of
gate transitions. A rising edge on PWM initiates the turn-off
of the lower MOSFET (see Timing Diagram). After a short
propagation delay [tPDLL], the lower gate begins to fall.
Typical fall times [tFL] are provided in the Electrical
Specifications section. Adaptive shoot-through circuitry
monitors the LGATE voltage and determines the upper gate
delay time [tPDHU]. This prevents both the lower and upper
MOSFETs from conducting simultaneously. Once this delay
period is complete, the upper gate drive begins to rise [tRU]
and the upper MOSFET turns on.
A falling transition on PWM results in the turn-off of the upper
MOSFET and the turn-on of the lower MOSFET. A short
propagation delay [tPDLU] is encountered before the upper
gate begins to fall [tFU]. Again, the adaptive shoot-through
circuitry determines the lower gate delay time, tPDHL. The
PHASE voltage and the UGATE voltage are monitored, and
the lower gate is allowed to rise after PHASE drops below a
level or the voltage of UGATE to PHASE reaches a level
depending upon the current direction (See next section for
details). The lower gate then rises [tRL], turning on the lower
MOSFET.
During turn-off of the lower MOSFET, the LGATE voltage is
monitored until it drops below 1.75V, at which time the
UGATE is released to rise after 20ns of propagation delay.
Once the PHASE is high, the adaptive shoot-through
circuitry monitors the PHASE and UGATE voltages during a
PWM falling edge and the subsequent UGATE turn-off. If
either the UGATE falls to less than 1.75V above the PHASE
or the PHASE falls to less than +0.8V, the LGATE is
released to turn on.
Three-State PWM Input
A unique feature of these drivers and other Intersil drivers is
the addition of a shutdown window to the PWM input. If the
PWM signal enters and remains within the shutdown window
for a set holdoff time, the driver outputs are disabled and
both MOSFET gates are pulled and held low. The shutdown
state is removed when the PWM signal moves outside the
shutdown window. Otherwise, the PWM rising and falling
thresholds outlined in the ELECTRICAL SPECIFICATIONS
determine when the lower and upper gates are enabled.
This feature helps prevent a negative transient on the output
voltage when the output is shut down, eliminating the
Schottky diode that is used in some systems for protecting
the load from reversed output voltage events.
In addition, more than 400mV hysteresis also incorporates
into the three-state shutdown window to eliminate PWM
6
FN6462.0
February 26, 2007
PX3511A, PX3511B
input oscillations due to the capacitive load seen by the
PWM input through the body diode of the controller’s PWM
output when the power-up and/or power-down sequence of
bias supplies of the driver and PWM controller are required.
200mV droop in drive voltage over the PWM cycle. We find
that a bootstrap capacitance of at least 0.267μF is required.
1.6
Power-On Reset (POR) Function
1.4
Pre-POR Overvoltage Protection
Prior to VCC exceeding its POR level, the upper gate is held
low and the lower gate is controlled by the overvoltage
protection circuits during initial startup. The PHASE is
connected to the gate of the low side MOSFET (LGATE),
which provides some protection to the microprocessor if the
upper MOSFET(s) is shorted during initial startup. For
complete protection, the low side MOSFET should have a
gate threshold well below the maximum voltage rating of the
load/microprocessor.
When VCC drops below its POR level, both gates pull low
and the Pre-POR overvoltage protection circuits are not
activated until VCC resets.
Internal Bootstrap Device
Both drivers feature an internal bootstrap schottky diode.
Simply adding an external capacitor across the BOOT and
PHASE pins completes the bootstrap circuit. The bootstrap
function is also designed to prevent the bootstrap capacitor
from overcharging due to the large negative swing at the
trailing-edge of the PHASE node. This reduces voltage
stress on the boot to phase pins.
The bootstrap capacitor must have a maximum voltage
rating above UVCC + 5V and its capacitance value can be
chosen from the following equation:
Q GATE
C BOOT_CAP ≥ -------------------------------------ΔV BOOT_CAP
(EQ. 1)
Q G1 • UVCC
Q GATE = ------------------------------------ • N Q1
V GS1
where QG1 is the amount of gate charge per upper MOSFET
at VGS1 gate-source voltage and NQ1 is the number of
control MOSFETs. The ΔVBOOT_CAP term is defined as the
allowable droop in the rail of the upper gate drive.
As an example, suppose two IRLR7821 FETs are chosen as
the upper MOSFETs. The gate charge, QG, from the data
sheet is 10nC at 4.5V (VGS) gate-source voltage. Then the
QGATE is calculated to be 53nC for UVCC (i.e. PVCC in
PX3511B, VCC in PX3511A) = 12V. We will assume a
7
1.2
CBOOT_CAP (µF)
During initial startup, the VCC voltage rise is monitored.
Once the rising VCC voltage exceeds 9.8V (typically),
operation of the driver is enabled and the PWM input signal
takes control of the gate drives. If VCC drops below the
falling threshold of 7.6V (typically), operation of the driver is
disabled.
1.
0.8
0.6
QGATE = 100nC
0.4
50nC
0.2
20nC
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
ΔVBOOT_CAP (V)
FIGURE 2. BOOTSTRAP CAPACITANCE vs BOOT RIPPLE
VOLTAGE
Gate Drive Voltage Versatility
The PX3511A and PX3511B provide the user flexibility in
choosing the gate drive voltage for efficiency optimization.
The PX3511A upper gate drive is fixed to VCC [+12V], but
the lower drive rail can range from 12V down to 5V
depending on what voltage is applied to PVCC. The
PX3511B ties the upper and lower drive rails together.
Simply applying a voltage from 5V up to 12V on PVCC sets
both gate drive rail voltages simultaneously.
Power Dissipation
Package power dissipation is mainly a function of the
switching frequency (FSW), the output drive impedance, the
external gate resistance, and the selected MOSFET’s
internal gate resistance and total gate charge. Calculating
the power dissipation in the driver for a desired application is
critical to ensure safe operation. Exceeding the maximum
allowable power dissipation level will push the IC beyond the
maximum recommended operating junction temperature of
+125°C. The maximum allowable IC power dissipation for
the SO8 package is approximately 800mW at room
temperature, while the power dissipation capacity in the DFN
package with an exposed heat escape pad is more than
1.5W. The DFN package is more suitable for high frequency
applications. See Layout Considerations paragraph for
thermal transfer improvement suggestions. When designing
the driver into an application, it is recommended that the
following calculation is used to ensure safe operation at the
desired frequency for the selected MOSFETs. The total gate
drive power losses due to the gate charge of MOSFETs and
the driver’s internal circuitry and their corresponding average
FN6462.0
February 26, 2007
PX3511A, PX3511B
driver current can be estimated with Equations 2 and 3,
respectively,
P Qg_TOT = P Qg_Q1 + P Qg_Q2 + I Q • VCC
BOOT
UVCC
D
CGD
(EQ. 2)
RHI1
Q G1 • UVCC 2
P Qg_Q1 = --------------------------------------- • F SW • N Q1
V GS1
RLO1
G
RG1
CDS
RGI1
CGS
Q1
• LVCC 2
Q G2
P Qg_Q2 = -------------------------------------- • F SW • N Q2
V GS2
S
PHASE
FIGURE 3. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
⎛ Q G1 • UVCC • NQ1 Q G2 • LVCC • N Q2⎞
I DR = ⎜ ------------------------------------------------------ + -----------------------------------------------------⎟ • F SW + I Q
V GS1
V GS2
⎝
⎠
(EQ. 3)
where the gate charge (QG1 and QG2) is defined at a
particular gate to source voltage (VGS1and VGS2) in the
corresponding MOSFET datasheet; IQ is the driver’s total
quiescent current with no load at both drive outputs; NQ1
and NQ2 are number of upper and lower MOSFETs,
respectively; UVCC and LVCC are the drive voltages for
both upper and lower FETs, respectively. The IQ*VCC
product is the quiescent power of the driver without
capacitive load and is typically 116mW at 300kHz.
The total gate drive power losses are dissipated among the
resistive components along the transition path. The drive
resistance dissipates a portion of the total gate drive power
losses, the rest will be dissipated by the external gate
resistors (RG1 and RG2) and the internal gate resistors
(RGI1 and RGI2) of MOSFETs. Figures 3 and 4 show the
typical upper and lower gate drives turn-on transition path.
The power dissipation on the driver can be roughly
estimated as:
P DR = P DR_UP + P DR_LOW + I Q • VCC
(EQ. 4)
R LO1
R HI1
⎛
⎞ P Qg_Q1
P DR_UP = ⎜ -------------------------------------- + ----------------------------------------⎟ • --------------------R
+
R
R
+
R
2
⎝ HI1
EXT1
LO1
EXT1⎠
R LO2
R HI2
⎛
⎞ P Qg_Q2
P DR_LOW = ⎜ -------------------------------------- + ----------------------------------------⎟ • --------------------R
+
R
R
+
R
2
⎝ HI2
EXT2
LO2
EXT2⎠
R GI1
R EXT1 = R G1 + ------------N
Q1
R GI2
R EXT2 = R G2 + ------------N
Q2
8
LVCC
D
CGD
RHI2
RLO2
G
RG2
CDS
RGI2
CGS
Q2
S
FIGURE 4. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
Layout Considerations
For heat spreading, place copper underneath the IC whether
it has an exposed pad or not. The copper area can be
extended beyond the bottom area of the IC and/or
connected to buried copper plane(s) with thermal vias. This
combination of vias for vertical heat escape, extended
copper plane, and buried planes for heat spreading allows
the IC to achieve its full thermal potential.
Place each channel power component as close to each
other as possible to reduce PCB copper losses and PCB
parasitics: shortest distance between DRAINs of upper FETs
and SOURCEs of lower FETs; shortest distance between
DRAINs of lower FETs and the power ground. Thus, smaller
amplitudes of positive and negative ringing are on the
switching edges of the PHASE node. However, some space
in between the power components is required for good
airflow. The traces from the drivers to the FETs should be
kept short and wide to reduce the inductance of the traces
and to promote clean drive signals.
FN6462.0
February 26, 2007
PX3511A, PX3511B
Dual Flat No-Lead Plastic Package (DFN)
2X
0.15 C A
D
A
L10.3x3
10 LEAD DUAL FLAT NO-LEAD PLASTIC PACKAGE
MILLIMETERS
2X
0.15 C B
SYMBOL
MIN
6
INDEX
AREA
0.80
0.90
1.00
-
-
-
0.05
-
0.28
5,8
2.05
7,8
1.65
7,8
0.20 REF
0.18
D
1.95
E
0.10 C
0.08 C
SIDE VIEW
C
SEATING
PLANE
1
e
1.60
-
0.50 BSC
-
k
0.25
-
-
L
0.30
0.35
0.40
N
10
Nd
5
8
2
3
1. Dimensioning and tolerancing conform to ASME Y14.5-1994.
2. N is the number of terminals.
NX k
E2/2
N-1
7. Dimensions D2 and E2 are for the exposed pads which provide
improved electrical and thermal performance.
NX b
5
(Nd-1)Xe
REF.
4. All dimensions are in millimeters. Angles are in degrees.
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.
NX L
e
3. Nd refers to the number of terminals on D.
5. Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
E2
8
1.55
NOTES:
D2/2
2
N
-
Rev. 3 6/04
D2
(DATUM B)
2.00
8
7
6
INDEX
AREA
(DATUM A)
A3
-
3.00 BSC
E2
A
0.23
3.00 BSC
D2
B
NOTES
A
b
TOP VIEW
MAX
A1
A3
E
NOMINAL
0.10 M C A B
8. Nominal dimensions are provided to assist with PCB Land
Pattern Design efforts, see Intersil Technical Brief TB389.
BOTTOM VIEW
C
L
0.415
NX (b)
(A1)
0.200
5
L
NX L
e
SECTION "C-C"
NX b
C
C C
TERMINAL TIP
FOR ODD TERMINAL/SIDE
9
FN6462.0
February 26, 2007
PX3511A, PX3511B
Small Outline Plastic Packages (SOIC)
M8.15 (JEDEC MS-012-AA ISSUE C)
N
8 LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE
INDEX
AREA
H
0.25(0.010) M
B M
INCHES
E
SYMBOL
-B-
1
2
3
L
SEATING PLANE
-A-
A
D
h x 45°
-C-
e
A1
B
0.25(0.010) M
C
0.10(0.004)
C A M
MIN
MAX
MIN
MAX
NOTES
A
0.0532
0.0688
1.35
1.75
-
A1
0.0040
0.0098
0.10
0.25
-
B
0.013
0.020
0.33
0.51
9
C
0.0075
0.0098
0.19
0.25
-
D
0.1890
0.1968
4.80
5.00
3
E
0.1497
0.1574
3.80
4.00
4
e
α
B S
0.050 BSC
1.27 BSC
-
H
0.2284
0.2440
5.80
6.20
-
h
0.0099
0.0196
0.25
0.50
5
L
0.016
0.050
0.40
1.27
6
N
α
NOTES:
MILLIMETERS
8
0°
8
8°
0°
7
8°
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
Rev. 1 6/05
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.
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.
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10
FN6462.0
February 26, 2007
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