UCD7231 Datasheet, PDF (1/31 Pages) Texas Instruments – Digital Control Compatible Synchronous-Buck Gate Driver With Current Sense and Fault Protection

UCD7231
www.ti.com
SLUS997 – NOVEMBER 2009 – REVISED JANUARY 2010
Digital Control Compatible Synchronous-Buck Gate Driver
With Current Sense and Fault Protection
Check for Samples: UCD7231
FEATURES
1
• Dual High Current Drivers.
• Full Compatibility with TI Fusion Digital Power
Supply Controllers, such as UCD91xx and
UCD92xx Families
• Operational to 2 MHz Switching Frequency
• High-Side FET and Output Current Limit
Protection with Independently Adjustable
Thresholds
• Fast High-Side Over-Current Sense Circuit
with Fault Flag Output – Prevents Catastrophic
Current Levels on a Cycle by Cycle Basis
• Differential High-Gain Current Sense Amplifier
• Voltage Proportional to Load Current Monitor
Output
• Wide Input Voltage Range: 4.7 V to 15 V
Operation to 2.2 V Input Supported with an
External 4.5-6.5 V Bias Supply
• Onboard Regulated Supplies for Gate Drive
and Internal Circuits
• Integrated Thermal Shutdown
• Selectable Operation Modes:
– PWM plus Synchronous Rectifier Enable
(SRE) with Automatic Dead-Time Control
– Direct High-Gate and Low-Gate Inputs for
Direct FET Control
• 3-State PWM Input for Power Stage Shutdown
• UVLO Housekeeping Circuit
• Rated from –40°C to +125°C Junction
Temperature
• Pb (Lead) Free Packaging
APPLICATIONS
• Digitally-Controlled Synchronous-Buck Power
Stages for Single- and Multi-Phase
Applications
• Digitally-Controlled Power Modules
DESCRIPTION
The UCD7231 high current driver is specifically
designed for digitally-controlled, point-of-load,
synchronous buck switching power supplies. Two
driver circuits provide high charge and discharge
current for the high-side NMOS switch and the
low-side NMOS synchronous rectifier in a
synchronous buck circuit. The MOSFET gates are
driven to +6 V by an internally regulated V_GG supply.
The internal V_GG regulator can be disabled to permit
the user to supply their own gate drive voltage. This
flexibility allows a wide power conversion input
voltage range of 2.2 to 15 V. Internal under voltage
lockout (UVLO) logic insures V_GG is good before
allowing chip operation.
A drive logic block allows operation in one of two
modes selected by the SRE Mode pin. In
Synchronous Mode, the logic block uses the PWM
signal to control both the high-side and low-side gate
drive signals. Dead time is automatically adjusted to
prevent cross conduction. The Synchronous Rectifier
Enable (SRE) pin controls whether or not the low-side
FET is turned on when the PWM signal is low. In
Independent Mode, the PWM and SRE pins control
the high-side and low-side gates directly. No
anti-cross-conduction logic is used in this mode.
On-board comparators monitor the voltage across the
high side switch and the voltage across an external
current sense element to safeguard the power stage
from sudden high current loads. Blanking delay is set
for the high side comparator by a single resistor in
order to avoid false reports coincident with switching
edge noise. In the event of a high-side fault or an
over-current fault, the high-side FET turned off and
the Fault Flag (FLT) is asserted to alert the digital
controller. The fault thresholds are independently set
by the HS Sense and ILIM pins.
Output current is measured and monitored by a
precision, high gain, switched capacitor differential
amplifier that processes the voltage present across
an external current sense element. The amplified
signal is available for use by the digital controller on
the I_MON pin. The current sense amplifier has output
offset of 0.5 V so that both positive (sourcing) and
negative (sinking) current can be sensed.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009–2010, Texas Instruments Incorporated