Transformer Volt- Second Product
and PWM Duty Cycle
High Current Gate Driver for Both
•
Main and Auxiliary Outputs
Multiple Protection Features with
•
Latched Shutdown and Soft Restart
• Low Supply Current (100µA Startup,
1.5mA Operation)
BLOCK DIAGRAM
DESCRIPTION
The UCC3580 family of PWM controllers is designed to implement a variety
of active clamp/reset and synchronous rectifier switching converter topolo
gies. While containing all the necessary functions for fixed frequency, high
performance pulse width modulation, the additional feature of this design is
the inclusion of an auxiliary switch driver which complements the main
power switch, and with a programmable deadtime or delay between each
transition. The active clamp/reset technique allows operation of single
ended converters beyond 50% duty cycle while reducing voltage stresses
on the switches, and allows a greater flux swing for the power transformer.
This approach also allows a reduction in switching losses by recovering en
ergy stored in parasitic elements such as leakage inductance and switch
capacitance.
The oscillator is programmed with two resistors and a capacitor to set
switching frequency and maximum duty cycle. A separate synchronized
ramp provides a voltage feedforward pulse width modulation and a pro
grammed maximum volt-second limit. The generated clock from the oscilla
tor contains both frequency and maximum duty cycle information.
(continued)
-
-
-
-
Pin Numbers refer to DIL-16 and SOIC-16 packages
SLUS292A - FEBRUARY 1999 - REVISED JANUARY 2002
UDG-95069-2
DESCRIPTION (cont.)
The main gate drive output (OUT1) is controlled by the
pulse width modulator. The second output (OUT2) is in
tended to activate an auxiliary switch during the off time
of the main switch, except that between each transition
there is deadtime where both switches are off, pro
grammed by a single external resistor. This design offers
two options for OUT2, normal and inverted. In the -1 and
-2 versions, OUT2 is normal and can be used to drive
PMOS FETs. In the -3 and -4 versions, OUT2 is inverted
and can be used to drive NMOS FETs. In all versions,
both the main and auxiliary switches are held off prior to
startup and when the PWM command goes to zero duty
cycle. During fault conditions, OUT1 is held off while
OUT2 operates at maximum duty cycle with a guaran
teed off time equal to the sum of the two deadtimes.
Undervoltage lockout monitors supply voltage (VDD), the
-
precision reference (REF), input line voltage (LINE), and
the shutdown comparator (SHTDWN).If after any of
these four have sensed a fault condition, recovery to full
-
operation is initiated with a soft start. VDD thresholds, on
and off, are 15V and 8.5V for the -2 and -4 versions, 9V
and 8.5V for the -1 and -3 versions.
The UCC1580-x is specified for operation over the mili
tarytemperature range of−55°C to 125°C. The
UCC2580-x is specified from −40°C to 85°C. The
UCC3580-x is specified from 0°C to 70°C. Package op
tions include 16-pin surface mount or dual in-line, and
20-pin plastic leadless chip carrier.
Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C
All voltages are with respect to ground unless otherwise stated.
Currents are positive into, negative out of the specified termi
nal. Consult Packaging Section of Databook for thermal limita
tions and considerations of packages.
= 12V, R1 = 18.2k, R2 = 4.41k, C
for the UCC2580, −55°C to 125°C for the UCC1580, T
PARAMETERTEST CONDITIONSMINTYPMAX UNITS
Output Drivers Section (cont.)
OUT2 Rise TimeC
Delay 1 OUT2 to OUT1R3 = 100k, C
Delay 2 OUT1 to OUT2R3 = 100k, C
Reference Section
REFI
Load RegulationI
Line RegulationVDD = 10V to 14V120mV
Note 1: Guaranteed by design. Not 100% tested in production.
= 100pF, R3 = 100k, C
T
Unless otherwise stated, all specifications are over the full temperature range, VDD
= 0, C
OUT1
.
A=TJ
= 300pF, RS= 10Ω2040ns
OUT2
OUT1
T
T
= 25°C100120140ns
A=TJ
OUT1
= 25°C140170200ns
A=TJ
= 04.87555.125V
REF
= 0mA to 1mA120mV
REF
= 0. TA= 0°C to 70°C for the UCC3580, −40°C to 85°C
OUT2
= C
= C
= 15pF90120160ns
OUT2
= 15pF110170250ns
OUT2
PIN DESCRIPTIONS
CLK: Oscillator clock output pin from a low impedance
CMOS driver. CLK is high during guaranteed off time.
CLK can be used to synchronized up to five other
UCC3580 PWMs.
DELAY: A resistor from DELAY to GND programs the
nonoverlap delay between OUT1 and OUT2. The delay
times, Delay1 and Delay2, are shown in Figure 1 and are
as follows:
DelaypFR
1113=•.
Delay2 is designed to be larger than Delay1 by a ratio
shown in Figure 2.
EAIN: Invertinginput tothe erroramplifier. The
noninverting input of the error amplifier is internally set to
2.5V. EAIN is used for feedback and loop compensation.
EAOUT: Output of the error amplifier and input to the
PWM comparator. Loop compensationcomponents
connect from EAOUT to EAIN.
GND: Signal Ground.
LINE: Hysteretic comparator input. Thresholds are 5.0V
and 4.5V. Used to sense input line voltage and turn off
OUT1 when the line is low.
OSC1 & OSC2: Oscillator programming pins. A resistor
connects each pin to a timing capacitor. The resistor
connected to OSC1 sets maximum on time. The resistor
connected to OSC2 controls guaranteed off time. The
combined total sets frequency with the timing capacitor.
Frequency and maximum duty cycle are approximately
given by:
Frequency
=
()
R1 1.25 R2CT
1
+••
Maximum Duty Cycle
=
Maximum Duty Cycle for OUT1 will be slightly less due to
Delay1 which is programmed by R3.
OUT1: Gate drive output for the main switch capable of
sourcing up to 0.5A and sinking 1A.
OUT2: Gate drive output for the auxiliary switch with
± 0.3A drive current capability.
PGND: Ground connection for the gate drivers. Connect
PGND to GND at a single point so that no high frequency
components of the output switching currents are in the
ground plane on the circuit board.
RAMP: A resistor (R4) from RAMP to the input voltage
and a capacitor (CR) from RAMP to GND programs the
feedforward ramp signal. RAMP is discharged to GND
when CLK is high and allowed to charge when CLK is
low. RAMP is the line feedforward sawtooth signal for the
PWM comparator. Assuming the input voltage is much
greater than 3.3V, the ramp is very linear. A flux
comparator compares the ramp signal to 3.3V to limit the
maximum allowable volt-second product:
Volt-Second Product Clamp = 3.3 • R4 • CR.
REF: Precision 5.0V reference pin. REF can supply up to
5mA to external circuits. REF is off until VDD exceeds 9V
(–1 and –3 versions) or activates the 15V clamp (–2 and
–4 versions) and turns off again when VDD droops below
8.5V. Bypass REF to GND with a 1µF capacitor.
SHTDWN: Comparator input to stop the chip. The
threshold is 0.5V. When the chip is stopped, OUT1 is low
and OUT2 continues to oscillate with guaranteed off time
equal to two non-overlap delay times.
4
R1
R1 1.25 R2
+•
PIN DESCRIPTIONS (cont.)
SS: A capacitor from SS to ground programs the soft
start time. During soft start, EAOUT follows the amplitude
of SS’s slowly increasing waveform until regulation is
achieved.
VDD: Chip power supply pin. VDD should be bypassed
to PGND. The –1 and –3 versions require VDD to exceed
9V to start and remain above 8.5V to continue running. A
shunt clamp from VDD to GND limits the supply voltage
to 15V. The –2 and –4 versions do not start until the
shunt clamp threshold is reached and operation contin
ues as long as VDD is greater than 8.5V.
-
Note: Waveforms are not to scale.
Figure 1. Output time relationships.
UVLO and Startup
For self biased off-line applications, -2 and -4 versions
(UVLO on and off thresholds of 15V and 8.5V typical)
are recommended. For all other applications, -1 and -3
versions provide the lower on threshold of 9V. The IC re
quires a low startup current of only 160µA when VDD is
under the UVLO threshold, enabling use of a large trickle
charge resistor (with corresponding low power dissipa
tion) from the input voltage. VDD has an internal clamp
at 15V which can sink up to 10mA. Measures should be
taken not to exceed this current. For -2 and -4 versions,
this clamp must be activated as an indication of reaching
the UVLO on threshold. The internal reference (REF) is
brought up when the UVLO on threshold is crossed. The
startup logic ensures that LINE and REF are above and
SHTDWN isbelow their respective thresholds before
outputs are asserted. LINE input is useful for monitoring
actual input voltage and shutting off the IC if it falls be
low a programmed value. A resistive divider should be
-
used to connect the input voltage to the LINE input. This
feature can protect the power supply from excessive
currents at low line voltages.
The soft start pin provides an effective means to start
the IC in a controlled manner. An internal current of
20µA begins charging a capacitor connected to SS once
the startup conditions listed above have been met. The
voltage on SS effectively controls maximum duty cycle
on OUT1 during the charging period. OUT2 is also con
trolled during this period (see Figure 1). Negation of any
of the startup conditions causes SS to be immediately
discharged. Internal circuitry ensures full discharge of
SS (to 0.3V) before allowing charging to begin again,
provided all the startup conditions are again met.
Oscillator
Simplified oscillator block diagram and waveforms are
shown in Figure 3. OSC1 and OSC2 pins are used to
program the frequency and maximum duty cycle. Capac
itor CT is alternately charged through R1 and dis
charged through R2 between levels of 1V and 3.5V. The
charging and discharging equations for CT are given by
t
-
τ
VC(charge) = REF – 4.0 • e
VC(discharge) = 3.5 • e
1
t
-
τ
2
-
-
-
Figure 3. Oscillator and ramp circuits.
UDG-96016-1
where τ1= R1 • CT and τ2= R2 • CT. The charge time
and discharge time are given by
CH = R1 • CT and tDIS = 1.25 • R2 • CT
t
The CLK output is high during the discharge period. It
blanks the output to limit the maximum duty cycle of
OUT1. The frequency and maximum duty cycle are
given by
Frequency =
(R1 + 1.25 • R2) • CT
Maximum Duty Cycle =
1
R1
R1 + 1.25 • R2
Maximum Duty Cycle for OUT1 will be slightly less due
to Delay1 which is programmed by R3.
Voltage Feedforward and Volt-Second Clamp
UCC3580 has a provision for input voltage feedforward.
As shown in Figure 3, the ramp slope is made propor
tional to input line voltage by converting it into a charging
current for CR. This provides a first order cancellation of
the effects of line voltage changes on converter perfor
mance. The maximum volt-second clamp is provided to
protect against transient saturation of the transformer
core. It terminates the OUT1 pulse when the RAMP volt
age exceeds 3.3V. If the feedforward feature is not used,
the ramp can be generated by tying R4 to REF. However,
the linearity of ramp suffers and in this case the maxi
mum volt-second clamp is no longer available.
6
-
-
-
-
APPLICATION INFORMATION (cont.)
Output Configurations
The UCC3580 family of ICs is designed to provide con
trol functions for single ended active clamp circuits. For
different implementations of the active clamp approach,
different drive waveforms for the two switches (main and
auxiliary) are required. The -3 and -4 versions of the IC
supplycomplementarynon-overlappingwaveforms
(OUT1 and OUT2) with programmable delay which can
be used to drive the main and auxiliary switches. Most
active clamp configurations will require one of these out
puts to be transformer coupled to drive a floating switch
(e.g. Figure 5). The -1 and -2 versions have the phase of
OUT2 inverted to give overlapping waveforms. This con
figuration is suitable for capacity coupled driving of a
ground referenced p-channel auxiliary switch with the
OUT2 drive while OUT1 is directly driving an n-channel
main switch (e.g. Figure 4).
The programmable delay can be judiciously used to get
zero voltage turn-on of both the main and auxiliary
switches in the active clamp circuits. For the UCC3580, a
single pin is used to program the delays between OUT1
and OUT2 on both sets of edges. Figure 1 shows the re
lationships between the outputs. Figure 2 gives the ratio
between the two delays. During the transition from main
to auxiliary switch, the delay is not very critical for ZVS
turn-on. For the first half of OUT1 off-time, the body di
ode of the auxiliary switch conducts and OUT2 can be
turned on any time. The transition from auxiliary to main
switch is more critical. Energy stored in the parasitic in
ductance(s) at the end of the OUT2 pulse is used to dis
charge the parasitic capacitance across the main switch
during the delay time. The delay (Delay 1) should be op
timally programmed at 1/4 the resonant period deter
mined by parasitic capacitance and the resonant
inductor (transformer leakage and/or magnetizing induc
tances, depending on the topology). However, depend
ing on other circuit parasitics, the resonant behavior can
change, and in some cases, ZVS turn-on may not be ob
tainable. It can be shown that the optimum delay time is
independent of operating conditions for a specific circuit
and should be determined specifically for each circuit.
Figure 5. Off-line active clamp flyback converter.
The use of active reset in a flyback power converter topology may be covered by U.S. Patent No. 5,402,329 owned by Technical
Witts, Inc., and for which Unitrode offers users a paid up license for application of the UCC1580 product family.
UCC3580QTR-3ACTIVEPLCCFN201000NoneCU SNPBLevel-2-220C-1 YEAR
UCC3580QTR-4ACTIVEPLCCFN201000NoneCU SNPBLevel-2-220C-1 YEAR
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Lead/Ball FinishMSL Peak Temp
(3)
(2)
Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
9-Mar-2005
Addendum-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. T esting and other quality control techniques are used to the extent TI
deems necessary to support this warranty . Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
ProductsApplications
Amplifiersamplifier.ti.comAudiowww.ti.com/audio
Data Convertersdataconverter.ti.comAutomotivewww.ti.com/automotive
DSPdsp.ti.comBroadbandwww.ti.com/broadband
Interfaceinterface.ti.comDigital Controlwww.ti.com/digitalcontrol
Logiclogic.ti.comMilitarywww.ti.com/military
Power Mgmtpower.ti.comOptical Networkingwww.ti.com/opticalnetwork
Microcontrollersmicrocontroller.ti.comSecuritywww.ti.com/security
Telephonywww.ti.com/telephony
Video & Imagingwww.ti.com/video
Wirelesswww.ti.com/wireless
Mailing Address:Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright 2005, Texas Instruments Incorporated
Loading...
+ hidden pages
You need points to download manuals.
1 point = 1 manual.
You can buy points or you can get point for every manual you upload.