TI UCC28220PW

 SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
FEATURES
D 2-MHz High Frequency Oscillator with 1-MHz
D
D
D
D
D
D
D
D
D
APPLICATIONS
D High Output Current (50-A to 100-A)
Operation Per Channel
Matched Internal Slope Compensation
Circuits
Programmable Maximum Duty Cycle Clamp
60% to 90% Per Channel
Peak Current Mode Control with
Cycle-by-Cycle Current Limit
Current Sense Discharge Transistor for
Improved Noise Immunity
Accurate Line Under and Over-Voltage Sense
with Programmable Hysteresis
Opto-Coupler Interface
110-V Internal Start-Up JFET (UCC28221)
Operates from 12-V Supply (UCC28220)
Programmable Soft-Start
D
D
D
Converters
Maximum Power Density Designs
High Efficiency 48-V Input with Low Output
Ripple Converters
High Power Offline, Telecom and Datacom
Power Supplies
DESCRIPTION
The UCC28220 and UCC28221 are a family of BiCMOS
interleaved dual channel PWM controllers. Peak
current mode control is used to ensure current sharing
between the two channels. A precise maximum duty
cycle clamp can be set to any value between 60% and
90% duty cycle per channel.
UCC28220 has an UVLO turn-on threshold of 10 V for
use in 12-V supplies while UCC28221 has a turn-on
threshold of 13 V for systems needing wider UVLO
hysteresis. Both have 8-V turn-off thresholds.
TYPICAL APPLICATION
VIN
(+48V)
CS1
UCC28221
1 LINEOV
VIN 16
Bias
2 LINE
HYS
LINEUV 15
3 VDD
REF 14
4 CS1
OUT1 13
5 SLOPE
OUT2 12
VOUT
1/2 UCC27324
6 CS2
GND 11
7 SS
CHG 10
CS2
REF
8 CTRL DISCHG 9
1/2 UCC27324
E/A
NOTE: Pin 16 is a no connect (N/C) on UCC28220 which does not include the JFET option.
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.
!" # $%&" !# '%()$!" *!"&+
*%$"# $ " #'&$$!"# '& ",& "&# &-!# #"%&"#
#"!*!* .!!"/+ *%$" '$&##0 *&# " &$&##!)/ $)%*&
"&#"0 !)) '!!&"&#+
Copyright  2004, Texas Instruments Incorporated
www.ti.com
1
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
DESCRIPTION (CONTINUED)
Additional features include a programmable internal slope compensation with a special circuit which is used to
ensure exactly the same slope is added to each channel and a high voltage 110-V internal JFET for easier
startup for the wider hysteresis UCC28221 version.
The UCC28220 is available in both 16-pin SOIC and low-profile TSSOP packages. The UCC28221 also comes
in 16-pin SOIC package and a slightly larger 20-pin TSSOP package to allow for high voltage pin spacing to
meet UL1950 creepage clearance safety requirements.
ORDERING INFORMATION
TEMPERATURE RANGE
TA = TJ
−40°C to +105°C
110-V HV JFET
STARTUP CIRCUIT
SOIC−16 (D)
TSSOP-16 (PW)
10 V on / 8 V off
NO
UCC28220D
UCC28220PW
−
13 V on / 8 V off
YES
UCC28221D
−
UCC28221PW
UVLO THRESHOLDS
PACKAGED DEVICES
TSSOP-20 (PW)
NOTE: D (SOIC) and PW (TSSOP) packages are available taped and reeled. Add R suffix to device type, e.g. UCC28220DR or UCC28221PWR.
The reel quanities are 2,500 devices per reel for D package and 2,000 devices per reel for the PW package.
CONNECTION DIAGRAM
UCC28220D, UCC28220PW
and UCC28221D PACKAGE
(TOP VIEW)
LINEOV
LINEHYS
VDD
CS1
SLOPE
CS2
SS
CTRL
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
UCC28221PW PACKAGE
(TOP VIEW)
VIN (for UCC28221)
N/C (for UCC28220)
LINEUV
REF
OUT1
OUT2
GND
CHG
DISCHG
1
2
3
4
5
6
7
8
9
10
N/C
LINEOV
LINEHYS
VDD
CS1
SLOPE
CS2
SS
CTRL
N/C
20
19
18
17
16
15
14
13
12
11
VIN
N/C
LINEUV
REF
OUT1
OUT2
GND
CHG
DISCHG
N/C
RECOMMENDED OPERATION CONDITIONS
Parameter
High voltage start-up input
Supply voltage
2
www.ti.com
Symbol
Condition
VIN
VDD
36 V to 76 V
8 V to 14.5 V
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature (unless otherwise noted)†}
Parameter
High voltage start-up input, VIN
UCC2822X
UNIT
110
V
Supply voltage, VDD
15
V
Output current (OUT1, OUT2) dc , IOUT(dc)
±10
mA
OUT1/ OUT2 capacitive load
200
pF
REF output current, IREF
10
mA
Current sense inputs, CS1, CS2
−1.0 to 2.0
V
Analog inputs (CHG, DISCHG, SLOPE, REF, CNTRL)
−0.3 to 3.6
V
Analog inputs (SS, LINEOV, LINEUV, LINEHYS)
−0.3 to 7.0
V
400
mW
Power dissipation at TA = 25°C (PW package)
Power dissipation at TA = 25°C (D package)
650
mW
Junction operating temperature, TJ
−55 to 150
°C
Storage temperature, Tstg
−65 to 150
°C
°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute−maximum−rated conditions for extended periods may affect device reliability.
‡ All voltages are with respect to GND. Currents are positive into, negative out of the specified terminal. Consult Packaging Section of the Databook
for thermal limitations and considerations of packages.
Lead temperature (soldering, 10 sec.), Tsol
300
ELECTRICAL CHARACTERISTICS:
VDD = 12 V, 0.1-µF capacitor from VDD to GND, 0.1-µF capacitor from REF to GND, FOSC = 1 MHz, TA = −40°C to
105°C, TA = TJ, (unless otherwise noted).
PARAMETER
TEST CONDITION
MIN
TYP
MAX
UNITS
14
V
Overall Section
Operating VDD range
8
Quiescent current
SS = 0 V, no switching, Fosc = 1 MHz
1.5
3
4
Operating current
Outputs switching, Fosc = 1 MHz
1.6
3.5
6
mA
Startup Section
Startup current
UCC28220 VDD < (UVLO−0.8)
200
Startup current
UCC28221 VDD < (UVLO−0.8)
500
UVLO start threshold
UCC28220
9.5
10
10.5
UVLO start threshold
UCC28221
12.3
13
13.7
7.6
8
8.4
2
2.2
UVLO stop threshold
UVLO hysteresis
UCC28220
1.8
UVLO hysteresis
UCC28221
4.8
5
5.2
JFET ON threshold
SS = 0, outputs not switching, VDD decreasing
9.5
10
10.5
JFET ON threshold
SS = 2 V,Cntrl = 2 V, output switching, VDD decreasing;
same threshold as UVLO stop
7.6
8
8.4
High voltage JFET current
VIN = 36 V to 76 V, VDD = 0 V
16
48
100
High voltage JFET current
VIN = 36 V to 76 V, VDD = 10 V
4
16
40
High voltage JFET current
VIN = 36 V to 76 V, VDD < UVLO
4
12
40
JFET leakage
VIN = 36 V to 76 V, VDD = 14 V
www.ti.com
100
A
µA
V
V
V
mA
µA
3
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
ELECTRICAL CHARACTERISTICS:
VDD = 12 V, 0.1-µF capacitor from VDD to GND, 0.1-µF capacitor from REF to GND, FOSC = 1 MHz, TA = −40°C to
105°C, TA = TJ, (unless otherwise noted).
PARAMETER
TEST CONDITION
MIN
TYP
MAX
3.15
3.3
3.45
UNITS
Reference
Output voltage
8 V < VDD < 14 V, ILOAD=0 mA to −10 mA
Output current
Outputs not switching; CNTRL = 0 V
Ouput short circuit current
VREF = 0 V
VREF UVLO
Soft-Start
10
−40
−20
−10
mA
2.55
3
3.25
V
SS charge current
RCHG=10.2 kΩ, SS = 0 V
−70
−100
−130
SS discharge current
RCHG=10.2 kΩ, SS = 2 V
70
100
130
SS initial voltage
LINEOV=2 V, LINEUV = 0 V
0.5
1
1.5
SS voltage at 0% dc
Point at which output starts switching
0.5
1.2
1.8
75%
90%
100%
3
3.5
4
SS voltage ratio
SS Max voltage
LINEOV = 0 V, LINEUV = 2 V
V
mA
µA
A
V
V
Oscillator and PWM
Output frequency
RCHG = 10.2 kΩ, RDISCHG = 10.2 kΩ
450
500
550
Oscillator frequency
RCHG = 10.2 kΩ, RDISCHG = 10.2 kΩ
900
1000
1100
Output maximum duty cycle
RCHG = 10.2 kΩ, RDISCHG = 10.2 kΩ, measured at OUT1
and OUT2
73%
75%
77%
CHG voltage
2
2.5
3
DISCHG voltage
2
2.5
3
140
200
260
0%
10%
kHz
%
V
Slope Compensation
Slope
RSLOPE = 75 kΩ, RCH = 66 kΩ, RDISCHG = 44 kΩ, Csx =
0 V to 0.5 V
Channel matching
RSLOPE = 75 kΩ, Csx = 0 V
mV/us
Current Sense
CS1, CS2 bias current
CS1 = 0, CS2 = 0
Prop delay CSx to OUTx
CSx input 0 V to 1.5 V step
−500
CS1, CS2 sink current
CSx = 2 V
2.3
CNTRL Section
Resistor ratio(1)
500
85
nA
ns
4.5
7
mA
0.6
Ctrl input current
CTRL = 0 V and 3.3 V
Ctrl voltage at 0% dc
CSx = 0 V, Point at which output starts switching (checks
resistor ratio)
NOTES: (1). Ensured by design. Not 100% tested in production.
4
0
40
www.ti.com
−100
0
100
nA
0.5
1.2
1.8
V
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
ELECTRICAL CHARACTERISTICS:
VDD = 12 V, 0.1-µF capacitor from VDD to GND, 0.1-µF capacitor from REF to GND, FOSC = 1 MHz, TA = −40°C to
105°C, TA = TJ, (unless otherwise noted).
PARAMETER
TEST CONDITION
MIN
TYP
MAX
UNITS
Output Section (OUT1, OUT2)
Low level
IOUT = 10 mA
IOUT = −10 mA, VREF – VOUT
0.4
1
High level
0.4
1
Rise time
CLOAD = 50 pF
10
20
Fall time
CLOAD = 50 pF
10
20
V
ns
LINE Sense section
LINEOV threshold
TA = 25°C
TA =−40°C to 105°C
1.240
1.260
1.280
1.235
1.260
1.285
1.240
1.260
1.280
LINEUV threshold
TA = 25°C
TA =−40°C to 105°C
1.235
1.260
1.285
LINEHYST pull up voltage
LINEOV = 2 V, LINEUV = 2 V
3.1
3.25
3.4
LINEHYST off leakage
LINEOV = 0 V, LINEUV = 2 V
−500
0
500
LINEHYS pull-up resistance
I = −20 µA
100
500
LINEHYS pull-down resistance
I = 20 µA
100
500
LINEOV, LINEUV bias I
LINEOV = 1.25 V, LINEUV = 1.25 V
LINEOV threshold
LINEUV threshold
−500
500
V
nA
Ω
nA
NOTES: (1). Ensured by design. Not 100% tested in production.
www.ti.com
5
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
FUNCTIONAL BLOCK DIAGRAM
REF
RUN
REFERENCE
14
16 VIN
(N/C on
UCC28220)
UVLO/ JFET
CONTROL
P2
CHG 10
T
OSC
DISCHG
9
CLK1
Q
FF
+
4
VDD
CLK2
Q
CS1
3
CLK1
+
S Q
LATCH
R
0.5 V
VREF
13 OUT1
Q
RUN
11
SLOPE
COMPENSATION
0.5 V
6
+
CS2
CLK2
+
S Q
LATCH
R
GND
VREF
12 OUT2
Q
RUN
SLOPE
5
CTRL
8
+
+
−
20 kΩ
1 LINEOV
30 kΩ
1 pF
LINE OV/UV
2 LINEHYS
15 LINEUV
Soft−Start
SS
7
RUN
NOTE: Pinout for 16 pin option shown. See the 20-pin connection to UCC28221PW in the Terminal Functions table on the next page.
6
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
Terminal Functions
TERMINAL
PIN NUMBER
FUNCTION
NAME
I/O
2
LINEOV
I
Input for line over voltage comparator
2
3
LINEHYS
I
Sets line comparator hysteresis
3
4
VDD
I
Device supply input
4
4
5
CS1
I
Channel 1 current sense input
5
5
6
SLOPE
I
Sets slope compensation
6
6
7
CS2
I
Channel 2 current sense input
7
7
8
SS
I
Soft-start input
8
8
9
CTRL
I
Feedback control input
9
9
12
DISCHG
I
Sets oscillator discharge current
10
10
13
CHG
I
Sets oscillator charge current
11
11
14
GND
−
Device ground
12
12
15
OUT2
O
PWM output from channel 2
13
13
16
OUT1
O
PWM output from channel 1
14
14
17
REF
O
Reference voltage output
15
15
18
LINEUV
I
Input for line under voltage comparator
−
16
20
VIN
I
High voltage start-up input
16
−
1, 10, 11, 19
N/C
−
No connection
UCC28220D
UCC28220PW
UCC28221D
UCC28221PW
1
1
2
3
PIN DESCRIPTIONS
VDD: This is used to supply power to the device, monitoring this pin is a the UVLO circuit. This is used to insure
glitch-free startup operation. Until VDD reaches its UVLO threshold, it remains in a low power mode, drawing
approximately 150 µA of current and forcing pins, SS, CS1, CS2, OUT1, and OUT2 to logic 0 states. If the VDD
falls below 8 V after reaching turn-on, it will go back into this low power state. In the case of the UCC28221, the
UVLO threshold is 13 V. It is 10 V for the UCC28220. Both versions have a turn-off threshold of 8 V.
VIN (UCC28221 only): This pin has an internal high voltage JFET used for startup. The drain is connected to
VIN, while its’ source is connected to VDD. During startup, this JFET delivers 12 mA typically with a minimum
of 4 mA to VDD, which in turn, charges up the VDD bypass capacitor. When VDD gets to 13 V, the JFET is turned
off.
CS1 and CS2: These 2 pins are the current sense inputs to the device. The signals are internally level shifted
by 0.5 V before the signal gets to the PWM comparator. Internally the slope compensation ramp is added to this
signal. The linear operating range on this input is 0 to 1.5 V. Also, this pin gets pulled to ground each time its
respective output goes low. (ie: OUT1 and OUT2).
SLOPE: This pin sets up a current used for the slope compensation ramp. A resistor to ground sets up a current,
which is internally divided by 25 and then applied to an internal 10-pF capacitor. Under normal operation th dc
voltage on this pin is 2.5 V..
SS: A capacitor to ground sets up the soft-start time for the open loop soft-start function. The source and sink
current from this pin is equal to 3/7th of the oscillator charge current set by the resistor on the CHG pin. The
soft start capacitor is held low during UVLO and during a Line OV or UV condition. Once an OV or UV fault
occurs, the soft-start capacitor is discharged by a current equal to its charging current. The capacitor does NOT
quickly discharge during faults. In this way, the controller has the ability to recover quickly from very short line
transients. This pin can also be used as an Enable/Disable function.
www.ti.com
7
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
CHG: A resistor from this pin to GND sets up the charging current of the internal CT capacitor used in the
oscillator. This resistor, in conjunction with the resistor on the DISCHG pin is used to set up the operating
frequency and maximum duty cycle. Under normal operation the dc voltage on this pin is 2.5 V.
DISCHG: A resistor from this pin to GND sets up the discharge current of the internal CT capacitor used in the
oscillator. This resistor, in conjunction with the resistor on the CHG pin is used to set up the operating frequency
and maximum duty cycle. Under normal operation the dc voltage on this pin is 2.5 V.
OUT1 and OUT2: These output buffers are intended to interface with high current MOSFET drivers. The output
drive capability is approximately 33 mA and has an output impedance of 100 Ω. The outputs swing between
GND and REF.
LINEOV: This pin is connected to a comparator and used to monitor the line voltage for an over voltage
condition. The typical threshold is 1.26 V.
LINEUV: This pin is connected to a comparator and used to monitor the line voltage for an under voltage
condition. The typical threshold is 1.26 V.
LINEHYST: This pin is controlled by both the LINEOV and LINEUV pins. It is used to control the hysteresis
values for both the over and under voltage line detectors.
REF: REF is a 3.3-V output used primarily as a source for the output buffers and other internal circuits. It is
protected from accidental shorts to ground. For improved noise immunity it is recommended that the reference
pin be bypassed with a minimum of 0.1 µF of capacitance to GND.
APPLICATION INFORMATION
General
The device is comprised of several housekeeping blocks as well as two slope compensated PWM channels that
are interleaved. The circuit is intended to run from an external VDD supply voltage between 8 V and 14 V,
however, the UCC28221 has the addition of a high voltage startup JFET with control circuitry which can be used
for system startup. Other functions contained in the device are supply UVLO, 3.3-V reference, accurate line OV
and UV functions, a high speed programmable oscillator for both frequency and duty cycle, programmable slope
compensation, and programmable soft start functions.
The UCC28220/1 is a primary side controller for a two channel interleaved power converter. The device is
compatible with forward or flyback converters as long as a duty cycle clamp between 60 and 90 percent is
required. The active clamp forward and flyback converters as well as the RCD and resonant reset forward
converters are therefore compatible with this device. To ensure the two channels share the total converter output
current, current mode control with internal slope compensation is used. Slope compensation is user
programmable via a dedicated pin and can be set over a 50:1 range, ensuring good small-signal stability over
a wide range of applications.
8
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
LINE Over Voltage and Under Voltage
Three pins are provided to turn-off the output drivers and reset the soft-start capacitor when the converter input
voltage is outside a prescribed range. The under-voltage set point and under-voltage hysteresis are accurately
set via external resistors. The over-voltage set point is also accurately set via a resistor ratio, but the hysteresis
is fixed by the same resistor that sets the u*nder-voltage hysteresis.
Figure 1 and 2 show detailed functional diagram and operation of the under voltage lockout (UVLO) and
over-voltage lockout (OVLO) features. The equations for setting the thresholds defined in Figure 2 are:
V1 + 1.26
R1
) 1.26
(R2 ) R3)
(1)
V2 + 1.26
(R1 ) Rx)
, where Rx + R4 Ŧ (R2 ) R3)
Rx
(2)
V4 + 1.26
(R1 ) R2 ) R3)
R3
(3)
ǒR1
Ǔ
R4
(4)
V3 + V4 * 1.26
The UVLO hysteresis and the OVLO hysteresis can then be calculated as V2 − V1 and V4 − V3, respectively.
By examining the design equations it becomes apparent that the value of R4 sets the amount of hysteresis at
both thresholds. By realizing this fact, the designer can then set the value of R4 based on the most critical
hysteresis specification either at high line or at low line. In most designs the value of R4 will be determined by
the desired amount of hysteresis around the UVLO threshold. As an example consider a telecom power supply
with the following input UVLO and OVLO design specifications:
•
•
•
•
V1 = 32.0 V
V2 = 34.0 V
V3 = 83.0 V
V4 = 84.7 V
Then,
•
•
•
R1 = 976 kΩ
R2 = 24.9 kΩ
R3 = 15.0 kΩ
and
•
R4 = 604 kΩ
www.ti.com
9
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
Input
Voltage
R1
UV
15
+
1.26 V
1.26 V
+
S1
OPEN
HYS
2
R4
S2
CLOSED
LINE_GOOD
R2
OV
1
+
R3
1.26 V
Figure 1. Line UVLO and OVLO Functional Diagram
ENABLE
LINE_GOOD
OFF
V1
V2
V3
V4
Figure 2. Line UVLO and OVLO Operation
VDD
Because the driver output impedance is high the energy storage requirements on the VDD capacitor is low. For
improved noise immunity it is recommended that the VDD pin, be bypassed with a minimum of 0.1 µF of
capacitance to GND. In most typical applications the bias voltage for the MOSFET drivers will also be used as
the VDD supply voltage for the chip. In the aforementioned applications it is beneficial to add a low valued
resistor between the bulk storage capacitor of the driver and the VDD capacitor for the UCC28220/1. By adding
a resistor in series with the bias supply any noise that is present on the bias supply will be filtered out before
getting to the VDD pin of the controller.
10
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
Reference
For improved noise immunity it is recommended that the reference pin, REF, be bypassed with a minimum of
0.1uF of capacitance to GND.
Oscillator Operation and Maximum Duty Cycle Setpoint
The oscillator uses an internal capacitor to generate the time base for both PWM channels. The oscillator is
programmable over a 200 kHz to 2MHz frequency range with 20% to 80% maximum duty cycle range. Both the
dead time and the frequency of the oscillator are divided by 2 to generate the PWM clock and off-time information
for each of the outputs. In this way, a 20% oscillator duty cycle corresponds to a 60% maximum duty cycle at
each output, where an 80% oscillator duty cycle yields a 90% duty cycle clamp at each output.
The design equations for the oscillator and maximum duty cycle set point are given by:
F OSC + 2
F OUT
D MAX(osc) + 1 * 2
R CHG + K OSC
R DISCHG + K OSC
(5)
ǒ1 * DMAX(out)Ǔ
(6)
D MAX(osc)
F OSC
(7)
ǒ1 * DMAX(osc)Ǔ
F OSC
(8)
Where:
•
•
•
•
•
•
•
KOSC = 2.04 x 1010 [Ω/s]
FOUT = Switching frequency at the outputs of the chip [Hz]
DMAX(out) = Maximum duty cycle limit at the outputs of the chip
DMAX(osc) = Maximum duty cycle of the Oscillator for the desired maximum duty cycle at the outputs
FOSC = Oscillator frequency for desired output frequency [Hz]
RCHG = External oscillator resistor which sets the charge current − [Ω]
RDISCHG = External oscillator resistor which sets the discharge current − [Ω]
Start-Up JFET Section
A 110-V start-up JFET is included to start the device from a wide range (36 V−75 V) telecom input source. When
VDD is lower than 13 V the JFET is on, behaving as a current source charging the bias capacitors on VDD and
supplying current to the device. In this way, the VDD bypass capacitors are charged to 13 V where the outputs
start switching and the JFET is turned off. To enable a constant bias supply to the device during a pulse skipping
condition, the JFET is turned back on whenever VDD decreases below 10 V and the outputs are not switching.
Thus, the current from the JFET can overcome the internal bias currents, as long as the device is not actively
switching the output drivers. See Figure 2 below for a graphical representation of the JFET/VDD operation. The
UCC28220 does not contain an internal JFET and has a startup threshold of 10 V which makes it capable of
directly operating off a 12 V dc bus
www.ti.com
11
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
VDD
13 V
13 V
8 − 14 V
10 V
NORMAL OPERATION
8 V (UVLO off)
0V
OUTx
GATE DRV
OFF
ON
ON
HV JFET
OFF
Figure 3. JFET Device Operation with VDD Voltage
Soft-Start
A current is forced out of the SS pin, equal to 3/7 of the current set by RCHG, to provide a controlled ramp voltage.
The current set by the RCHG resistor is equal to 2.5 V divided by RCHG. This ramp voltage overrides the
commanded duty cycle on the CTRL pin, allowing a controlled start-up. Assuming the UCC28221 is biased on
the primary side, the soft start should be quite quick to allow the secondary bias to be generated and the
secondary side control can then take over. Once the soft-start time interval is complete, a closed loop soft-start
on the secondary side can be executed.
ISS + 3
7
2.5
R CHG
(9)
where,
ISS = current which is sourced out of the SS pin during the soft-start time − [Amps]
Current Sense
The current sense signals CS1 and CS2 are level shifted by 0.5 V and have the slope compensation ramps
added to them before being compared to the control voltage at the input of the PMW comparators. The
amplitude of the current sense signal at full load should be selected such that it is very close to the maximum
control voltage in order to limit the peak output current during short circuit operation.
Output Drivers
The UCC28220/1 is intended to interface with the UCC27323/4/5 family of MOSFET drivers. As such, the output
drive capability is low, effectively 100 Ω and the driver outputs swing between GND and REF.
12
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
Slope Compensation
The slope compensation circuit in the UCC28220/1 operates on a cycle-by-cycle basis. The two channels have
separate slope compensation circuits. These are fabricated in precisely the same way so as current sharing
is unaffected by the slope compensation circuit. For each channel, an internal capacitor is reset whenever that
channel’s output is off. At the beginning of the PWM cycle, a current is mirrored off the SLOPE pin into the
capacitor, developing an independent ramp. Since the two channel’s ramps will start when the channel’s output
changes from a low to high state, the ramps are thus interleaved. These internal ramps are added to the voltages
on the current sense pins, CS1 and CS2 and the result forms an input to the PWM comparators.
REF
SLOPE
(5)
2.5/(25*R_SLOPE) = I_SC
R_SLOPE
CTRL
(8)
PWM −
+
+
TO RESET
of
PWM LATCH
0.5V
C_SC
OUT 1
ON
S1
10 pF
OFF
CS1
(4)
S2
Figure 4. Slope Compensation Detail for Channel 1. Duplicate Matched Circuitry Exists for Channel 2.
To ensure stability, the slope compensation circuit must add between 1/5 and 1 times the inductor downslope
to each of the current sense signals prior to being applied to the PWM comparator’s input.
www.ti.com
13
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
Determining the value for the slope compensation resistor:
Design Example:
NCT(p) = 1
VOUT = 12
LOUT = 3.2 x 10 −6
NCT(s) = 50
Np = 7
RSENSE = 5.23
Ns = 5
VEA(cl) = 1.98
FS(out) = 500000
Where,
•
•
•
•
•
•
•
•
•
NCT(p) = Number of primary turns on the Current Transformer − [Turns]
NCT(s) = Number of Secondary turns on the current transformer − [Turns]
VOUT = Nominal output voltage of the converter − [V]
LOUT = Inductance value of each output inductor − [H]
NP = Number of primary turns on the main transformer − [Turns]
NS = Number of secondary turns on the main transformer − [Turns]
RSENSE = Value of current sense resistor on secondary of current sense transformer − [Ohms]
VEA(cl) = Maximum Value of the E/A output voltage − [Volts]
FS(out) = Switching frequency of each output − [Hz]
Determine the correct value for the slope resistor, RSLOPE, to provide the desired amount of slope
compensation.
N CT +
N CT(p)
N CT(s)
, Current Transformer Turns Ratio
1. Transform the Secondary Inductor Downslope to the Primary
S L(prime) +
V OUT
L OUT
Ns
,
Np
S L(prime) + 2.679 Ańms
2. Calculate the Transformed Slope Voltage at Sense Resistor:
VS L(prime) + S L(prime)
N CT
R SENSE,
VS L(prime) + 2.281 Vńms
3. Calculate the RSLOPE value to give a compensating ramp equal to the transformed slope voltage given
above.:
M + 1.0
Desired ratio between the compensating ramp and the output inductor downslope ramp, transformed to the
primary sense resistor
R SLOPE +
14
ǒM
10 4
VS L(prime)
Ǔ
10 *6
,
R SLOPE + 35.556 kW
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
TYPICAL APPLICATION CIRCUITS
VIN
CS1
UCC28221
1 OV
VIN 16
2 HYS
UV 15
3 VDD
REF 14
Bias
VOUT
1/2 UCC27424
4 CS1
OUT1 13
5 SLOPE
OUT2 12
CS2
6 CS2
GND 11
7 SS
CHG 10
8 CTRL
DISCHG 9
1/2 UCC27424
REF
E/A
Figure 5. Interleaved Flyback Application Circuit Using the UCC28221
www.ti.com
15
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
VIN
CS1
UCC28220
1
OV
2
HYS
UV 15
3
VDD
REF 14
4
CS1
OUT1 13
5
SLOPE
OUT2 12
N/C 16
Bias
1/2 UCC27424
VOUT
CS2
6
CS2
GND 11
7
SS
CHG 10
8
CTRL
1/2 UCC27424
DISCHG 9
E/A
Figure 6. Interleaved Boost Application Circuit Using the UCC28220
16
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
TYPICAL CHARACTERISTICS
QUIESCENT CURRENT
vs
SUPPLY VOLTAGE
UVLO THRESHOLDS
vs
TEMPERATURE
4.0
13.5
3.5
11.5
UCC28220 UVLO on threshold and UCC28221
JFET on threshold (when not switching)
10.5
9.5
8.5
UCC28221 EXCLUDES JFET CURRENT
3.0
2.5
2.0
1.5
1.0
UCC28220 and UCC28221 UVLO off threshold and
UCC28221 JFET on threshold (when switching)
0.5
7.5
0.0
−50
−25
0
25
50
75
100
125
0
2
4
6
8
10
12
14
16
VDD − Supply Voltage − V
Tj − Temperature − °C
Figure 7
Figure 8
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
REFERENCE VOLTAGE
vs
TEMPERATURE
3.45
30
VIN = 36 V
3.40
VREF − ReferenceVoltage − V
20
IDD − Supply Current − mA
UCC28221
12.5
UCC28220
IDD − Quiescent Current − mA
VUVLO − UVLO Thresholds− V
UCC28221 UVLO on threshold
UCC28221
10
0
−10
−20
−30
3.35
3.30
No Load
3.25
Load
3.20
−40
JFET source current
3.15
−50
0
2
4
6
8
10
12
14
16
−50
−25
0
25
50
75
100
125
Tj − Temperature − °C
VDD − Supply Voltage − V
Figure 9
Figure 10
www.ti.com
17
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
TYPICAL CHARACTERISTICS
LINEOV AND LINEUV THRESHOLDS
vs
TEMPERATURE
SLOPE COMPENSATION
vs
TEMPERATURE
1.270
230
225
LINEOV
1.260
Vth − Trip Threshold − V
SLOPE − Slope Compensation − mV per µs
1.265
1.255
1.250
LINEUV
1.245
1.240
1.235
1.230
RSLOPE = 75 kΩ
220
215
210
205
CS1 = 0 V
200
195
190
CS1 = 0.5 V
185
180
175
170
−50
−25
0
25
50
75
100
125
−50
Tj − Temperature − °C
−25
0.0
75
100
125
Figure 12
CHANNEL1 AND CHANNEL2 SLOPE MATCHING
vs
TEMPERATURE
PROGRAMMING RESISTOR
vs
SLOPE COMPENSATION
10
106
8
6
4
105
Mismatch − %
RSLOPE − Slope Programming Resistor − Ω
50
Tj − Temperature − °C
Figure 11
2
0
RSLOPE = 75 kΩ
CS0 = 0 V
CS1 = 0 V
−2
104
−4
−6
−8
−10
103
10
100
SLOPE − Slope Compensation − mV per µs
1000
−50
−25
0.0
25
50
Tj − Temperature − °C
Figure 14
Figure 13
18
25
www.ti.com
75
100
125
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
TYPICAL CHARACTERISTICS
RISE AND FALL TIME
vs
TEMPERATURE (CL = 50 pf)
VOH AND VOL
vs
TEMPERATURE
1.0
0.9
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
IOUT = 10 mA
0.8
VO -Output Voltage − V
Tr and Tf − Rise and Fall Time − ns
20
19
18
17
Fall Time
Rise Time
0.7
VREF − VOUT (VOH)
0.6
0.5
0.4
VOL
0.3
0.2
0.1
−50
−25
0
25
50
75
100
0.0
125
−50
−25
0
25
50
75
Tj − Temperature − °C
Tj − Temperature − °C
Figure 15
100
125
Figure 16
SOFTSTART DISCHARGE CURRENT
vs
TEMPERATURE
SOFTSTART CHARGE CURRENT
vs
TEMPERATURE
130
−70
120
−80
ISSdis − Charge Current − µA
ISSCH − Charge Current − µA
RCHG = 10.2 kΩ
−90
−100
−110
110
100
90
−120
80
−130
70
−50
−25
0
25
50
75
100
125
−50
−25
0
25
50
75
100
125
Tj − Temperature − °C
Tj − Temperature − °C
Figure 18
Figure 17
www.ti.com
19
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
TYPICAL CHARACTERISTICS
PROGRAMMING RESISTORS
vs
SWITCHING FREQUENCY
OSCILLATOR FREQUENCY
vs
TEMPERATURE
1M
550
RCHRG = RDISRG = 10.2 kΩ
530
RCHRG = RDISRG
DMAX = 75%
100K
fS - Oscillator Frequency − kHz
RCHRG RDISRG − Resistance − Ω
540
10K
1K
520
510
500
490
480
470
460
450
10K
100K
1M
10M
−50
fS - Switching Frequency − Hz
−25
0
25
50
75
100
125
Tj − Temperature − °C
Figure 19
Figure 20
CSx to OUTx delay
vs
CSx Peak Voltage
PROGRAMMABLE MAX DUTY CYCLE
vs
TEMPERATURE
100
77
90
CSx to OUTx delay − ns
RCHRG = RDISRG = 10.2 kΩ
DC − Duty Cycle − %
76
75
105°C
80
70
60
25°C
50
−40°C
40
30
74
20
10
0
73
−50
−25
0
25
50
75
100
125
Tj − Temperature − °C
0.2
0.4
0.6 0.8
1.0 1.2
CSx − Peak Voltage − V
Figure 22
Figure 21
20
0
www.ti.com
1.4
1.6
1.8
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
APPLICATION INFORMATION
Related Products
DEVICE
DESCRIPTION
PACKAGE OPTION
UCC27323/4/5
Dual 4-A High Speed Low Side MOSFET Drivers
SOIC-8, PowerPAD MSOP-8, PDIP-8
UCC27423/4/5
Dual 4-A High Speed Low Side MOSFET Drivers
with Enable
SOIC-8, PowerPAD MSOP-8, PDIP-8
TPS2811/12/13
Dual 2.4-A High Speed Low Side MOSFET Drivers
SOIC-8, TSSOP-8, PDIP-8
UC3714/15
Dual 2.4-A High Speed Low Side MOSFET Drivers
SOIC-8, PowerSOIC-14, PDIP-8
References and Resources:
An evaluation module and an associated user’s guide are available. The UCC28221 is used in a two-channel
interleaved Forward design converting from 36-V to 76-V dc input voltage to a regulated 12-V dc output. The
power module has two isolated 100 W forward power stages operating at 500 kHz, which are operating 180
degrees out of phase with each other allowing for output current ripple cancellation and smaller magnetic
design. This design also takes advantage of the UCC28221’s on-board 110-V internal JFET start up circuit that
removes the need of an external trickle charge resistor for boot strapping. This circuit turns off after auxiliary
power is supplied to the device conserving power.
D Evaluation Module, UCC28221EVM, 48 VIN, 12 VOUT, 200-W Interleaved Forward Converter
D User’s Guide, UCC28221 Evaluation Module, Texas Instruments Literature Number SLUU173
www.ti.com
21
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
MECHANICAL DATA
D (R-PDSO-G**)
PACKAGE
PLASTIC SMALL-OUTLINE
8 PINS SHOWN
0.020 (0,51)
0.014 (0,35)
0.050 (1,27)
8
0.010 (0,25)
5
0.008 (0,20) NOM
0.244 (6,20)
0.228 (5,80)
0.157 (4,00)
0.150 (3,81)
Gage Plane
1
4
0.010 (0,25)
0°− 8°
A
0.044 (1,12)
0.016 (0,40)
Seating Plane
0.010 (0,25)
0.004 (0,10)
0.069 (1,75) MAX
PINS **
0.004 (0,10)
8
14
16
A MAX
0.197
(5,00)
0.344
(8,75)
0.394
(10,00)
A MIN
0.189
(4,80)
0.337
(8,55)
0.386
(9,80)
DIM
4040047/E 09/01
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or
protrusion, not to exceed 0.006 (0,15).
D. Falls within JEDEC MS-012
22
www.ti.com
SLUS544A − SEPTEMBER 2003 − REVISED AUGUST 2004
MECHANICAL DATA
PW (R-PDSO-G**)
PACKAGE
PLASTIC SMALL-OUTLINE
14 PINS SHOWN
0,30
0,19
0,65
14
0,10 M
8
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
0,25
1
7
0°−ā 8°
A
0,75
0,50
Seating Plane
0,15
0,05
1,20 MAX
PINS **
0,10
8
14
16
20
24
28
A MAX
3,10
5,10
5,10
6,60
7,90
9,80
A MIN
2,90
4,90
4,90
6,40
7,70
9,60
DIM
4040064/F 01/97
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or
protrusion not to exceed 0,15.
D. Falls within JEDEC MO-153
www.ti.com
23
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. Testing 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:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DSP
dsp.ti.com
Broadband
www.ti.com/broadband
Interface
interface.ti.com
Digital Control
www.ti.com/digitalcontrol
Logic
logic.ti.com
Military
www.ti.com/military
Power Mgmt
power.ti.com
Optical Networking
www.ti.com/opticalnetwork
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
Telephony
www.ti.com/telephony
Video & Imaging
www.ti.com/video
Wireless
www.ti.com/wireless
Mailing Address:
Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright  2004, Texas Instruments Incorporated