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FAN3111 Schematic ( PDF Datasheet ) - Fairchild Semiconductor

Teilenummer FAN3111
Beschreibung Low-Side Gate Driver
Hersteller Fairchild Semiconductor
Logo Fairchild Semiconductor Logo 




Gesamt 18 Seiten
FAN3111 Datasheet, Funktion
www.DataSheet4U.com
April 2009
FAN3111 — Single 1A High-Speed, Low-Side
Gate Driver
Features
ƒ 1.4A Peak Sink / Source at VDD = 12V
ƒ 1.1A Sink / 0.9A Source at VOUT = 6V
ƒ 4.5 to 18V Operating Range
ƒ FAN3111C Compatible with FAN3100C Footprint
ƒ Two Input Configurations:
Dual CMOS Inputs Allow Configuration as
Non-Inverting or Inverting with Enable Function
Single Non-Inverting, Low-Voltage Input for
Compatibility with Low-Voltage Controllers
ƒ Small Footprint Facilitates Distributed Drivers for
Parallel Power Devices
ƒ 15ns Typical Delay Times
ƒ 9ns Typical Rise / 8ns Typical Fall times with
470pF Load
ƒ 5-Pin SOT23 Package
ƒ Rated from –40°C to 125°C Ambient
Description
The FAN3111 1A gate driver is designed to drive an N-
channel enhancement-mode MOSFET in low-side
switching applications.
Two input options are offered: FAN3111C has dual
CMOS inputs with thresholds referenced to VDD for use
with PWM controllers and other input-signal sources
that operate from the same supply voltage as the driver.
For use with low-voltage controllers and other input-
signal sources that operate from a lower supply voltage
than the driver, that supply voltage may also be used as
the reference for the input thresholds of the FAN3111E.
This driver has a single, non-inverting, low-voltage input
plus a DC input VXREF for an external reference voltage
in the range 2 to 5V.
The FAN3111 is available in a lead-free finish industry-
standard 5-pin SOT23.
Applications
ƒ Switch-Mode Power Supplies
ƒ Synchronous Rectifier Circuits
ƒ Pulse Transformer Driver
ƒ Logic to Power Buffer
ƒ Motor Control
Figure 1. FAN3111C (Top View)
© 2008 Fairchild Semiconductor Corporation
FAN3111 • Rev. 1.0.1
Figure 2. FAN3111E (Top View)
www.fairchildsemi.com






FAN3111 Datasheet, Funktion
www.DataSheet4U.com
Timing Diagrams
90%
Output
10%
VINH
IN+ VINL
tD1 tD2
tRISE
tFALL
Figure 5. Non-Inverting Waveforms
90%
Output
10%
VINH
IN - VINL
tD1 tD2
tFALL
tRISE
Figure 6. Inverting Waveforms
© 2008 Fairchild Semiconductor Corporation
FAN3111 • Rev. 1.0.1
6
www.fairchildsemi.com

6 Page









FAN3111 pdf, datenblatt
www.DataSheet4U.com
Applications Information
The FAN3111 offers CMOS- or logic-level-compatible
input thresholds. In the FAN3111C, the logic input
thresholds are dependent on the VDD level and, with VDD
of 12V, the logic rising-edge threshold is approximately
55% of VDD and the input falling-edge threshold is
approximately 38% of VDD. The CMOS input
configuration offers a hysteresis voltage of
approximately 17% of VDD. The CMOS inputs can be
used with relatively slow edges (approaching DC) if
good decoupling and bypass techniques are
incorporated in the system design to prevent noise from
violating the input-voltage hysteresis window. This
allows setting precise timing intervals by fitting an R-C
circuit between the controlling signal and the IN pin of
the driver. The slow rising edge at the IN pin of the
driver introduces a delay between the controlling signal
and the OUT pin of the driver.
In the FAN3111E, the input thresholds are dependent
on the VXREF voltage that typically is chosen between 2V
and 5V. This range of VXREF allows compatibility with
TTL and other logic levels up to 5V by connecting the
XREF pin to the same source as the logic circuit that
drives the FAN3111E input stage. The logic rising edge
threshold is approximately 50% of VXREF and the input
falling-edge threshold is approximately 30% of VXREF.
The TTL-like input configuration offers a hysteresis
voltage of approximately 20% of VXREF.
Startup Operation
The FAN3111 internal logic is optimized to drive ground
referenced N-channel MOSFETs as VDD supply voltage
rises during startup operation. As VDD rises from 0V to
approximately 2V, the OUT pin is held LOW by an
internal resistor, regardless of the state of the input
pins. When the internal circuitry becomes active at
approximately 2V, the output assumes the state
commanded by the inputs.
Figure 35 illustrates FAN3111C startup operation with
VDD increasing from 0 to 12V, with the output
commanded to the low level (IN+ and IN- tied to
ground). Note that OUT is held LOW to maintain an N-
channel MOSFET in the OFF state.
VDD
OUT
FAN3111C
OUT @ 5 V/Div
VDD @ 5 V/Div
t = 200 us/Div
Figure 35. FAN3111C Startup Operation
Figure 36 illustrates startup operation as VDD increases
from 0 to 12V with the output commanded to the high
level (IN+ tied to VDD, IN- tied to GND). This
configuration might not be suitable for driving high-side
P-channel MOSFETs because the low output voltage of
the driver would attempt to turn the P-channel MOSFET
on with low VDD levels.
VDD
OUT
FAN3111C
OUT @ 5 V/Div
VDD @ 5 V/Div
t = 200 us/Div
Figure 36. Startup Operation as VDD Increases
Figure 37 illustrates FAN3111E startup operation with the
output commanded to the low level (IN+ tied to ground)
and the voltage on XREF ramped from 0 to 3.3V.
XREF
VDD
OUT
FAN3111E
VDD @ 5 V/Div
OUT @ 2 V/Div
VXREF @ 2 V/Div
t = 50 us/Div
Figure 37. FAN3111E Startup Operation
MillerDrive™ Gate Drive Technology
FAN3111 drivers incorporate the MillerDrive
architecture shown in Figure 38 for the output stage, a
combination of bipolar and MOS devices capable of
providing large currents over a wide range of supply-
voltage and temperature variations. The bipolar devices
carry the bulk of the current as OUT swings between
1/3 to 2/3 VDD and the MOS devices pull the output to
the high or low rail.
The purpose of the MillerDrive architecture is to speed
up switching by providing the highest current during the
Miller plateau region when the gate-drain capacitance of
the MOSFET is being charged or discharged as part of
the turn-on / turn-off process. For applications with zero
voltage switching during the MOSFET turn-on or turn-off
interval, the driver supplies high peak current for fast
switching even though the Miller plateau is not present.
This situation often occurs in synchronous rectifier
applications because the body diode is generally
conducting before the MOSFET is switched on.
© 2008 Fairchild Semiconductor Corporation
FAN3111 • Rev. 1.0.1
12
www.fairchildsemi.com

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