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UCD8220
SLUS652E – MARCH 2005 – REVISED APRIL 2020
UCD8220 Digitally Managed Push-Pull Analog PWM Controllers
1 Features
•
1
•
•
•
•
•
•
•
•
•
•
•
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•
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•
•
For digitally managed power supplies using μCs
or the TMS320 ™ DSP family
Voltage or peak current mode control with cycleby-cycle current limiting
Clock input from digital controller to set operating
frequency and max duty cycle
Analog PWM comparator
2-MHz switching frequency
110-V input startup circuit and thermal shutdown
(UCD8620)
Internal programmable slope compensation
3.3-V, 10-mA linear regulator
DSP/μC compatible inputs
Dual ±4-A TrueDrive™ integrated circuit high
current drivers
10-ns typical rise and fall times with 2.2-nF
25-ns input-to-output propagation delay
25-ns current sense-to-output propagation delay
Programmable current-limit threshold
Digital output current-limit flag
4.5-V to 15.5-V supply voltage range
Rated from –40°C to 105°C
2 Applications
•
•
•
Digitally managed switch mode power supplies
Push-pull, half-bridge, or full-bridge converters
Battery chargers
3 Description
The UCD8220 analog pulse-width modulator (PWM)
device is used in digitally managed power supplies
using a microcontroller or the TMS320 DSP family.
Systems using the UCD8220 device close the PWM
feedback loop with traditional analog methods, but
the UCD8220 controller includes circuitry to interpret
a time-domain digital pulse train. The pulse train
contains the operating frequency and maximum duty
cycle limit which are used to control the power supply
operation. The device circuitry eases implementation
of a converter with high level control features without
the added complexity or possible PWM resolution
limitations of closing the control loop in the discrete
time domain.
The UCD8220 device can be configured for either
peak current mode or voltage mode control. The
device provides a programmable current-limit function
and a digital output current-limit flag which can be
monitored by the host controller to set the current
limit operation. For fast switching speeds, the output
stage uses the TrueDrive output circuit architecture,
which delivers rated current of ±4-A into the gate of a
MOSFET. Finally the device also includes a 3.3-V,
10-mA linear regulator to provide power to the digital
controller or act as a reference in the system.
The UCD8220 controller is compatible with the
standard 3.3-V I/O ports of UCD9K digital power
controllers, DSPs, microcontrollers, or ASICs and is
offered in the PowerPAD™ integrated circuit package
HTSSOP.
Device Information(1)
PART NUMBER
UCD8220
PACKAGE
HTSSOP (16)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Figure 1. UCD8220 Typical Simplified Push-Pull
Converter Application Schematic
The UCD8220 device is a double-ended PWM
controller configured with push-pull drive logic.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
UCD8220
SLUS652E – MARCH 2005 – REVISED APRIL 2020
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
4
4
4
4
5
6
7
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ................................................
Typical Characteristics ..............................................
Detailed Description ............................................ 12
7.1 Overview ................................................................. 12
7.2 Functional Block Diagram ....................................... 13
7.3 Feature Description................................................. 13
7.4 Device Functional Modes........................................ 17
8
Application and Implementation ........................ 18
8.1 Application Information............................................ 18
8.2 Typical Application ................................................. 18
9 Power Supply Recommendations...................... 22
10 Layout................................................................... 23
10.1 Layout Guidelines ................................................. 23
10.2 Layout Example .................................................... 23
10.3 Thermal Considerations ........................................ 24
11 Device and Documentation Support ................. 24
11.1
11.2
11.3
11.4
Documentation Support ........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
24
24
24
24
12 Mechanical, Packaging, and Orderable
Information ........................................................... 24
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision D (October 2006) to Revision E
Page
•
Added the following sections to the data sheet: Device Functional Modes, Application Information, Design
Requirements, Application Curves, Power Supply Recommendations, and Layout Example............................................... 1
•
Changed Updated ESD table ................................................................................................................................................ 4
•
Changed Junction temperature to 105 Celsius ...................................................................................................................... 5
•
Changed Junction temperature to 105 Celsius ...................................................................................................................... 6
•
Added Layout example for Industrial version ...................................................................................................................... 23
2
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5 Pin Configuration and Functions
PWP Package
16-Pin HTSSOP With PowerPAD
Top View
NC
1
2
3
4
5
6
7
8
CLK
3V3
ISET
AGND
CTRL
CLF
ILIM
16
15
14
13
12
11
10
9
NC
NC
VDD
PVDD
OUT1
OUT2
PGND
CS
NC – No internal connection
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
3V3
3
O
Regulated 3.3-V rail. The onboard linear voltage regulator is capable of sourcing up to 10 mA of
current. Place a 0.22-μF ceramic capacitor from this pin to analog ground.
AGND
5
—
Analog ground return
CLF
7
O
Current-limit flag. When the CS level is greater than the ILIM voltage minus 25 mV, the output
driver is forced low and the current-limit flag (CLF) is set high. The CLF signal is latched high until
the device receives the next rising edge on the CLK pin. This signal is also used for the start-up
handshaking between the digital controller and the analog controller
CLK
2
I
Clock. Input pulse train contains operating frequency and maximum duty cycle limit. This pin is a
high impedance digital input capable of accepting 3.3-V logic level signals up to 2 MHz. An internal
Schmitt trigger comparator isolates the internal circuitry from any external noise.
CS
9
I
Current sense pin. A fast current-limit comparator connected to the CS pin is used to protect the
power stage by implementing cycle-by-cycle current limiting.
CTRL
6
I
Input for the error feedback voltage from the external error amplifier. This input is multiplied by 0.5
and routed to the negative input of the PWM comparator
ILIM
8
I
Current-limit threshold set pin. The current-limit threshold can be set to any value between 0.25 V
and 1 V. The default value while open is 0.5 V.
ISET
4
I
Pin for programming the current used to set the amount of slope compensation in peak currentmode control or to set the internal capacitor charging in voltage-mode control.
NC
15
1
—
No connection.
16
OUT1
12
O
The high-current TrueDrive integrated circuit driver output.
OUT2
11
O
The high-current TrueDrive integrated circuit driver output.
PGND
10
—
Power ground return. This pin should be connected close to the source of the power MOSFET.
PVDD
13
—
Supply pin provides power for the output drivers. This pin is not connected internally to the VDD
supply rail. The bypass capacitor for this pin should be returned to PGND.
VDD
14
I
Supply input pin to power the control circuitry. Bypass the pin with a capacitor with a value of at
least 4.7 μF, returned to AGND.
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6 Specifications
6.1 Absolute Maximum Ratings (1) (2)
MIN
MAX
UNIT
16
V
Supply voltage, VDD
Supply current, IDD
Output gate-drive voltage, VO
Quiescent
20
Switching, TA = 25°C, TJ = 105°C, VDD = 12 V
200
OUTx
–1
PVDD
Output gate-drive sink current, IO(sink) OUTx
A
OUTx
Analog input
ISET, CS, CTRL, ILIM
–0.3
3.6
Digital I/Os
CLK, CLF
–0.3
3.6
–4
Continuous total power dissipation
V
See Thermal Information
Operating junction temperature range, TJ
–55
Lead temperature (Soldering, 10 sec)
Storage temperature, Tstg
(2)
V
4
Output gate-drive source current,
IO(source)
(1)
mA
–65
150
°C
300
°C
150
°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.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
Human body model (HBM)
Electrostatic discharge
(1)
UNIT
±2000
Charged device model (CDM)
V
±500
Tested to JEDEC standard EIA/JESD22-A114-B specification.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
VDD
Supply voltage, PVDD
MIN
MAX
UNIT
4.5
15.5
V
6.4 Thermal Information
THERMAL METRIC (1)
PWP (HTSSOP)
16 PINS
RθJA
Junction-to-ambient thermal resistance
40.1
RθJC(top)
Junction-to-case (top) thermal resistance
29.5
RθJB
Junction-to-board thermal resistance
24.2
ψJT
Junction-to-top characterization parameter
ψJB
Junction-to-board characterization parameter
24
RθJC(bot)
Junction-to-case (bottom) thermal resistance
1.8
(1)
4
1
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 Electrical Characteristics
VDD = 12 V, 4.7-µF capacitor from VDD to AGND, 1 μF from PVDD to PGND, 0.22-µF capacitor from 3V3 to AGND, TA = TJ =
–40°C to 105°C, (unless otherwise noted).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
300
500
µA
3
mA
SUPPLY SECTION
Supply current, OFF
VDD = 4.2 V
Supply current, ON
Outputs not switching, CLK = low
2
LOW VOLTAGE UNDERVOLTAGE LOCKOUT
VDD UVLO ON
4.25
4.5
4.75
V
VDD UVLO OFF
4.05
4.25
4.45
V
VDD UVLO hysteresis
150
250
350
mV
3.267
3.3
3.333
3.234
3.3
3.366
1
6.6
mV
REFERENCE / EXTERNAL BIAS SUPPLY
3V3 initial set point
TA = 25°C, ILOAD = 0
3V3 set point over temperature
V
V
3V3 load regulation
ILOAD = 1 mA to 10 mA, VDD = 5 V
3V3 line regulation
VDD = 4.75 V to 12 V, ILOAD = 10 mA
1
6.6
mV
Short circuit current
VDD = 4.75 to 12 V
11
20
35
mA
3V3 OK threshold, ON
3.3 V rising
2.9
3.0
3.1
V
3V3 OK threshold, OFF
3.3 V falling
2.7
2.8
2.9
V
CLOCK INPUT (CLK)
VIT+
HIGH, positive-going input
threshold voltage
1.65
2.08
V
VIT–
LOW negative-going input
threshold voltage
1.16
1.5
V
(VIT+) –
(VIT–)
Input voltage hysteresis
0.6
0.8
V
Frequency
OUTx = 1 MHz
2
MHz
SLOPE COMPENSATION (ISET)
ISET Voltage
m
VSLOPE (I-Mode)
m
VSLOPE (V-Mode)
VISET , 3V3 = 3.3 V, ±2%
1.78
1.84
1.90
RISET = 6.19 kΩ to AGND, CS = 0.25 V,
CTRL = 2.5 V
1.48
2.12
2.76
RISET = 100 kΩ to AGND, CS = 0.25 V,
CTRL = 2.5 V
0.099
0.142
0.185
RISET = 499 kΩ to AGND, CS = 0.25 V,
CTRL = 2.5 V
0.019
0.028
0.037
RISET = 4.99 kΩ to 3V3, CTRL = 2.5 V
1.44
2.06
2.68
RISET = 100 kΩ to 3V3, CTRL = 2.5 V
0.079
0.114
0.148
RISET = 402 kΩ to 3v3, CTRL = 2.5 V
0.019
0.027
0.035
V
V/µs
V/µs
ISET resistor range
Current mode control; RISET connected to
AGND
6.19
499
kΩ
ISET resistor range
Voltage mode control; RISET connected to
3V3
4.99
402
kΩ
ISET current range
Voltage mode control with Feed-Forward;
RISET connected to VIN
3.7
300
μA
PWM offset at CTRL input
3V3 = 3.3 V ±2%
CTRL buffer gain (1)
Gain from CTRL to PWM comparator input
PWM
(1)
0.45
0.51
0.6
0.5
V
V/V
Specified by design. Not 100% tested in production.
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Electrical Characteristics (continued)
VDD = 12 V, 4.7-µF capacitor from VDD to AGND, 1 μF from PVDD to PGND, 0.22-µF capacitor from 3V3 to AGND, TA = TJ =
–40°C to 105°C, (unless otherwise noted).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
CURRENT LIMIT (ILIM)
ILIM internal current limit
threshold
ILIM = OPEN
0.466
0.5
0.536
V
ILIM maximum current limit
threshold
ILIM = 3.3 V
0.975
1.025
1.075
V
ILIM current limit threshold
ILIM = 0.75 V
0.700
0.725
0.750
V
ILIM minimum current limit
threshold
ILIM = 0.25 V
0.2
0.23
0.25
V
CLF output high level
CS > ILIM , ILOAD = –7 mA
CLF output low level
CS ≤ ILIM, ILOAD = 7 mA
2.64
V
0.66
V
CURRENT SENSE COMPARATOR
Bias voltage
Includes CS comp offset
5
Input bias current
25
50
–1
mV
μA
CURRENT SENSE DISCHARGE TRANSISTOR
Discharge resistance
CLK = low, resistance from CS to AGND
10
35
75
Ω
OUTPUT DRIVERS
Source current (1)
VDD = 12 V, CLK = high, OUTx = 5 V
4
A
Sink current (1)
VDD = 12 V, CLK = low, OUTx = 5 V
4
A
A
Source current
(1)
VDD = 4.75 V, CLK = high, OUTx = 0
2
Sink current (1)
VDD = 4.75 V, CLK = low, OUTx = 4.75 V
3
Output with VDD < UVLO
VDD = 1.0 V, ISINK = 10 mA
0.8
A
1.2
V
6.6 Timing Requirements
VDD = 12 V, 4.7-µF capacitor from VDD to AGND, 1 μF from PVDD to PGND, 0.22-µF capacitor from 3V3 to AGND, TA = TJ =
–40°C to 105°C, (unless otherwise noted).
MIN
NOM
MAX
UNIT
CLOCK INPUT (CLK)
Minimum allowable off time (1)
20
ns
ns
CURRENT LIMIT (ILIM)
Propagation delay from CLK to
CLF
CLK rising to CLF falling after a current limit
event
15
25
Propagation delay from CS to
OUTx
ILIM = 0.5 V, measured on OUTx, CS =
threshold + 60 mV
25
40
Propagation delay from CS to
CLF
ILIM = 0.5 V, measured on CLF, CS = threshold
+ 60 mV
25
50
CURRENT SENSE COMPARATOR
ns
OUTPUT DRIVERS
tR
Rise time
CLOAD = 2.2 nF, VDD = 12 V, See Figure 2
10
20
tF
Fall time
CLOAD = 2.2 nF, VDD = 12 V, See Figure 2
10
15
tD1
Propagation delay from CLK to
OUTx, CLK rising
CLOAD = open, VDD = 12 V, See Figure 2
25
35
tD2
Propagation delay from CLK to
OUTx, CLK falling
CLOAD = open, VDD = 12 V, See Figure 2
25
35
(1)
6
ns
ns
Specified by design. Not 100% tested in production.
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VIT+
INPUT
VIT−
tF
tF
t D1
90%
t D2
OUTPUT
10%
Figure 2. Timing Diagram
6.7 Typical Characteristics
3.36
5.0
UVLO on
4.5
3.34
UVLO off
Reference Voltage, 3V3 (V)
UVLO Thresholds (V)
4.0
3.5
3.0
2.5
2.0
1.5
3.32
3.30
3.28
1.0
3.26
0.5
0.0
−50
UVLO hysteresis
3.24
−25
0
25
50
75
100
125
−50
−25
0
25
50
75
Temperature (°C)
Temperature (°C)
100
125
Figure 4. 3V3 Reference Voltage vs Temperature
Figure 3. UCD8220 UVLO Threshold vs Temperature
160
23.0
140
22.5
CLOAD = 10 nF
Supply Current (mA)
Short Circuit Current (mA)
120
22.0
VDD = 4.75 V
21.5
VDD = 12 V
21.0
100
80
CLOAD = 4.7 nF
60
40
20.5
20
CLOAD = 1 nF
0
20.0
−50
CLOAD = 2.2 nF
−25
0
25
50
Temperature (°C)
75
100
125
0
500
1000
1500
Frequency (kHz)
Figure 5. 3V3 Short-circuit Current vs Temperature
Figure 6. Supply Current vs Frequency (VDD = 5 V)
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Typical Characteristics (continued)
280
320
240
280
240
Supply Current (mA)
Supply Current (mA)
CLOAD = 10 nF
200
160
CLOAD = 4.7 nF
120
80
CLOAD = 10 nF
200
160
CLOAD = 4.7 nF
120
80
CLOAD = 2.2 nF
40
CLOAD = 2.2 nF
40
CLOAD = 1 nF
0
0
500
0
1500
1000
CLOAD = 1 nF
0
500
Figure 8. Supply Current vs Frequency (VDD = 10 V)
Figure 7. Supply Current vs Frequency (VDD = 8 V)
400
500
450
350
400
CLOAD = 10 nF
Supply Current (mA)
Supply Current (mA)
300
250
CLOAD = 4.7 nF
200
150
CLOAD = 10 nF
350
300
CLOAD = 4.7 nF
250
200
150
100
CLOAD = 2.2 nF
CLOAD = 2.2 nF
100
50
50
CLOAD = 1 nF
CLOAD = 1 nF
0
0
500
0
0
1500
1000
1500
1000
500
Frequency (kHz)
Frequency (kHz)
Figure 9. Supply Current vs Frequency (VDD = 12 V)
Figure 10. Supply Current vs Frequency (VDD = 15 V)
2.5
18
16
CLK Input Rising
2.0
t R = Rise Time
14
Rise and Fall Times (ns)
CLK Input Voltage (V)
1500
1000
Frequency (kHz)
Frequency (kHz)
1.5
CLK Input Falling
1.0
12
10
t F = Fall Time
8
6
4
0.5
2
0
0.0
−50
−25
0
25
50
75
100
125
−50
−25
25
50
75
100
125
Temperature (°C)
Temperature (°C)
CLOAD = 2.2 nF
Figure 11. CLK Input Threshold vs Temperature
8
0
VDD = 12 V
Figure 12. Output Rise Time and Fall Time vs Temperature
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Typical Characteristics (continued)
65
45
40
55
35
CLOAD = 10 nF
CLOAD = 10 nF
Output Fall Time (ns)
Output Rise Time (ns)
45
35
CLOAD = 4.7 nF
25
CLOAD = 2.2 nF
30
25
CLOAD = 4.7 nF
20
CLOAD = 2.2 nF
15
15
CLOAD = 1 nF
10
CLOAD = 1 nF
5
5
5
7.5
10
12.5
15
5
7.5
Supply Voltage (V)
Figure 13. Output Rise Time vs Supply Voltage
15
Figure 14. Output Fall Time vs Supply Voltage
Propagation Delay, Falling (ns)
Propagation Delay, Rising (ns)
12.5
25
20
CLOAD = 10 nF
15
10
CLOAD = 4.7 nF
5
CLOAD = 2.2 nF
CLOAD = 10 nF
20
15
CLOAD = 4.7 nF
10
CLOAD = 2.2 nF
CLOAD = 1 nF
CLOAD = 1 nF
5
0
5
7.5
10
12.5
15
5
7.5
Figure 15. CLK to OUTx Propagation Delay Rising vs Supply
Voltage
0.58
35
CS to OUTx Propagation Delay (ns)
40
0.57
0.56
0.55
0.54
0.53
25
20
15
10
5
0.51
0
0
25
50
15
30
0.52
−25
12.5
Figure 16. CLK to OUTx Propagation Delay Falling vs
Supply Current
0.59
−50
10
Supply Voltage (V)
Supply Voltage (V)
Current Limit Threshold (V)
10
Supply Voltage (V)
75
100
125
−50
−25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
Figure 17. Default Current Limit Threshold vs Temperature
Figure 18. CS to OUTx Propagation Delay vs Temperature
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Typical Characteristics (continued)
50
35
45
25
35
Propagation Delay (ns)
CS to CLF Propagation Delay (ns)
30
40
30
25
20
15
20
15
10
10
5
5
0
0
−50
−25
0
25
50
75
100
125
−50
−25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
Figure 19. CS to CLF Propagation Delay vs Temperature
Figure 20. CLK to OUT Propagation Delay vs Temperature
VDD (2 V/div)
VDD (2 V/div)
3V3 (2 V/div)
3V3 (2 V/div)
OUTx (2 V/div)
OUTx (2 V/div)
Time − 40 ms/div
Time − 40 ms/div
CLK = CTRL = 3V3
CLK = CTRL = 3V3
Figure 21. Start-Up Behavior at VDD = 12 V
Figure 22. Shut-Down Behavior at VDD = 12 V
VDD (2 V/div)
VDD (2 V/div)
3V3 (2 V/div)
3V3 (2 V/div)
OUTx (2 V/div)
OUTx (2 V/div)
Time − 40 ms/div
Time − 40 ms/div
CLK = AGND
CLK = AGND
CTRL = 3V3
Figure 23. Start-Up Behavior at VDD = 12 V
10
CTRL = 3V3
Figure 24. Shut-Down Behavior at VDD = 12 V
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Typical Characteristics (continued)
Output V oltage − 2 V/div
Internal Slope Compensation in CMC (V/ms)
0.146
0.144
0.142
0.140
0.138
0.136
0.134
−50
−25
Time − 40 ns/div
VDD = 12 V
0
25
50
75
100
125
Temperature (°C)
CLOAD = 10 nF
Current mode slope
Figure 25. Output Rise and Fall Time
RISET = 100 kΩ
Figure 26. Internal Slope Compensation in CMC vs
Temperature
0.532
PWM Offset at CTRL Input (V)
0.530
0.528
0.526
0.524
0.522
0.520
0.518
−50
−25
0
25
50
75
100
125
Temperature (°C)
Figure 27. PWM Offset at CTRL Input vs Temperature
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7 Detailed Description
7.1 Overview
The UCD8220 device is a digitally managed analog PWM controller that is configured with push-pull drive logic.
In systems using the UCD8220 device, the PWM feedback loop is closed using the traditional analog methods.
However, the UCD8220 includes circuitry to interpret a time-domain digital pulse train from a digital controller.
The pulse train contains the operating frequency and maximum duty-cycle limit and therefore controls the power
supply operation. The device circuitry eases the implementation of a converter with high-level control features
without the added complexity or digital PWM-resolution limitations encountered when closing the voltage controlloop in the discrete time domain.
The UCD8220 device can be configured for either peak current-mode or voltage-mode control. The device
provides a programmable current-limit function and a digital output current limit flag which can be monitored by
the host controller. For fast switching speeds, the output stages use the TrueDrive output-circuit architecture,
which delivers rated current of ±4-A into the gate of a MOSFET during the Miller plateau region of the switching
transition. Finally the device also includes a 3.3-V, 10-mA linear regulator to provide power for the digital
controller.
The UCD8220 device includes circuitry and features to ease implementing a converter that is managed by a
microcontroller or a digital signal processor. Digitally managed power supplies provide software programmability
and monitoring capability of the operation of the power supply, including:
• Switching frequency
• Synchronization
• DMAX
• V × S clamp
• Input UVLO start and stop voltage
• Input OVP start and stop voltage
• Soft-start profile
• Current-limit operation
• Shutdown
• Temperature shutdown
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7.2 Functional Block Diagram
16 NC
NC 1
15 NC
CLK 2
3V3 3
14 VDD
3V3 Regulator
and
Reference
UVLO
13 PVDD
12 OUT1
DRIVE
LOGIC
11 OUT2
ISET 4
PWM
PWM
10 PGND
CTRL 6
AGND 5
CLF 7
CURRENT
LIMIT
CURRENT
SENSE
ILIM 8
9 CS
7.3 Feature Description
7.3.1 CLK Input Time-Domain Digital Pulse Train
While the loop is closed in the analog domain, the UCD8220 device is managed by a time-domain digital pulse
train from a digital controller. The pulse train, shown as CLK in Figure 28, contains the operating frequency and
maximum duty-cycle limit and therefore controls the power supply operation as previously listed. The pulse train
uses a Texas Instruments communication protocol which is a proprietary communication system that provides
control of the power supply operation through software programming. The rising edge of the CLK signal
represents the switching frequency. Figure 28 depicts the operation of the UCD8220 device in one of five modes.
At the time when the internal signal REF OK is low, the UCD8220 device is not ready to accept CLK inputs.
When the REF OK signal goes high, then the device is ready to process inputs. While the CLK input is low, the
outputs are disabled and the CLK signal is used as an enable input. When the digital controller completes the
initialization routine and verifies that all voltages are within operating range, then the controller begins the softstart procedure by slowly ramping up the duty cycle of the CLK signal, while maintaining the desired switching
frequency. The CLK duty cycle continues to increase until it reaches steady-state where the analog control loop
takes over and regulates the output voltage to the desired set point. During steady state, the duty cycle of the
CLK pulse can be set using a volt-second product calculation to protect the primary of the power transformer
from saturation during transients.
When the power supply detects an overcurrent event, it enters the current-limit mode where the outputs are
quickly turned off and the CLF signal is set high to notify the digital controller that the last power pulse was
truncated. This technique is beneficial because it allows the digital controller to decide how to handle this
overcurrent event while providing some protection to the other components being supplied by this device.
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Feature Description (continued)
The software is now in charge of the response to overcurrent events. In typical analog designs, the power supply
response to overcurrent is hardwired in the silicon. With this method, the user can configure the response
differently for different applications. For example, the software can be configured to latch-off the power supply in
response the first overcurrent event, or to allow a fixed number of current-limit events, so that the supply is
capable of starting up into a capacitive load. The user can also configure the supply to enter into hiccup mode
immediately or after a certain number of current-limit events. As described later in this data sheet, the current
limit threshold can be varied in time to create unique current limit profiles. For example, the current limit set point
can be set high for a predefined number of cycles to blow a manual fuse, and can be reduced down to protect
the system in the event of a faulty fuse.
(1)
(2)
Start up (3)
Steady State (4)
Current Limit (5)
UVLO and
REF OK*
CLK
CTRL
RAMP*
PWM*
OUT
CS
CLF
*
- Internal signals
Figure 28. Timing and Circuit Operation Diagram
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7.3.2 Current Sensing and Protection
40 kW
20 kW
10 kW
2.5 kW
Figure 29. ILIM Settings
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7.3.3 Handshaking
The UCD8220 device has a built-in handshaking feature to facilitate efficient start-up of the digitally managed
power supply. At start-up the CLF flag is held high until all the internal and external supply voltages of the
UCD8220 device is within its operating range. When the supply voltages are within acceptable limits, the CLF
flag goes low and the device processes the CLK signals. The digital controller should monitor the CFL flag at
start-up and wait for the CLF flag to go low before sending CLK pulses to the UCD8220 device.
7.3.4 Driver Output
The high-current output stage of the UCD8220 device is capable of supplying ±4-A peak current pulses and
swings to both the PVDD and PGND pins.
The drive output uses the TI's TrueDrive output-circuit architecture, which delivers rated current into the gate of a
MOSFET when it is most needed, during the Miller plateau region of the switching transition providing efficiency
gains.
The TrueDrive integrated circuit consists of pullup and pulldown circuits with bipolar and MOSFET transistors in
parallel. The peak output current rating is the combined current from the bipolar and MOSFET transistors. This
hybrid output stage also allows efficient current sourcing at low supply voltages.
7.3.5 Source and Sink Capabilities During Miller Plateau
Large power MOSFETs present a large load to the control circuitry. Proper drive is required for efficient, reliable
operation. The UCD8220 driver has been optimized to provide maximum drive to a power MOSFET during the
Miller plateau region of the switching transition. This interval occurs while the drain voltage is swinging between
the voltage levels dictated by the power topology, requiring the charging or discharging of the drain-gate
capacitance with current supplied or removed by the driver device. See (5) in the Related Documentation
section.
7.3.6 Drive Current and Power Requirements
The UCD8220 device contains drivers that can deliver high current into a MOSFET gate for a period of several
hundred nanoseconds. High-peak current is required to turn on a MOSFET. To turn off a MOSFET, the driver is
required to sink a similar amount of current to ground. This cycle repeats at the operating frequency of the power
device.
For additional information on the current required to drive a power MOSFET and other capacitive-input switching
devices, see (5) in the Related Documentation section.
When a driver device is tested with a discrete, capacitive load, calculating the power that is required from the
bias supply is fairly simple. Use Equation 1 to calculate the energy that must be transferred from the bias supply
to charge the capacitor.
E = 1 x CV 2
2
where
•
•
C is the load capacitor
V is the bias voltage feeding the driver
(1)
An equal amount of energy is transferred to ground when the capacitor is discharged. This transfer of energy
results in a power loss which is calculated with Equation 2.
P = CV 2 x f
where
•
f is the switching frequency
(2)
This power is dissipated in the resistive elements of the circuit. Thus, with no external resistor between the driver
and gate, this power is dissipated inside the driver. Half of the total power is dissipated when the capacitor is
charged, and the other half is dissipated when the capacitor is discharged.
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Use Equation 3 to calculate the power loss with the following values: VDD = 12 V, CLOAD = 2.2 nF, and f = 300
kHz.
P = 2.2 nF x 122 x 300 kHz = 0.095 W
(3)
Use Equation 4 to calculate the current with a 12-V supply.
0.095 W = 7.9 mA
P
=
I =
V
12 V
(4)
7.3.7 Clearing the Current-Limit Flag (CLF)
In the UCD8220 design, the CLF signal is cleared by the comparator (compares the voltage between the CS and
ILIM pins) output. However, the comparator output is enabled by the OUTx pin. Therefore, the CLF signal does
not clear (go low) unless one or both OUTx pins are on, which enables the comparator output. Pulling the CTRL
pin high turns the OUTx pin on which is why the CLF flag only clears when CTRL is high (greater than 0.45 to
0.6 V). Therefore, anything that turns on the OUTs pins enables the comparator, and if V_CS is less than
V_ILIM, the comparator output clears the CLF signal. The CLF signal goes low during the next rising edge on the
CLK pin after these conditions are met.
CLK
Q
CLK
VDD
Ramp
+
COMP
±
CTRL
17
D
QZ
A
B
VSS
A
DTC20
IV110
CLRZ
Y
NO210
A
DTC0
NOR0
Y
B
AN210
Y
A
IV110
OUT1
Y
AND0
BUF1
INV3
A
IV110
OUT2
Y
BUF2
A
B
OR210
Y
A
IV110
OR1
ILIM
VDD
+
COMP
±
CS
INV0
15
SET
A
B
OR210
V3P3
Q
D
Y
OR0
D_FF
VSS
CLK
Y
IV110
A
IV110
Y
CLF
INV1
QB
RESET GND
A
A
INV4
IV110
Y
INV2
Figure 30. Logic Circuit for CLF
7.4 Device Functional Modes
The device has no additional functional modes.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The UCD8220 device can be configured for either peak current mode or voltage mode control. The device can
be used to implement a variety of applications such as push-pull, half-bridge, or full-bridge converter.
8.2 Typical Application
Using the UCD8220 device in an application, a high degree of digital control can be achieved because the device
integrates the PWM, logic, error amplifier, current limit, and drivers. In addition, the on-chip regulator provides
power to the microcontroller. An example application is using the device in half-bridge power topology.
Figure 31. UCD8220 Typical Simplified Half-Bridge Converter Application Schematic
8.2.1 Design Requirements
When designing a half-bridge system, the key requirement is determining which functions should remain in the
digital domain rather than the analog domain. The design shown in allows for a high degree of control over
various blocks such as PWM, logic, error amplifier, current limit, and drivers. The UCD8220 closes the control
loop for the power supply and provides the loop compensation. During operation, the UCD8220 monitors current
and terminates the switching cycle safely if the value exceeds the current limit. By performing this task in the
UCD8220, the device assists in real-time and full-time safety. The UCD8220 device provides notification of
overcurrent events to the microcontroller. The notification of overcurrent events to the microcontroller allows the
microcontroller to have a more complex response strategy. The firmware can, for example, direct the system to
tolerate a finite number of current events, go to soft-stop, or shut down.
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Typical Application (continued)
8.2.2 Detailed Design Procedure
Current limit is set through a simple resistor divider at the ISET pin. In the case of an overcurrent limit, the
UCD8220 device sets the current flag (CF) pin high and the device is turned off by the host controller if the
current limit exceeds a certain number of cycles. Depending upon the control method, the ISET resistor can be
selected as previously mentioned.
8.2.2.1 Selecting the ISET Resistor for Voltage Mode Control
3V3
3V3
(3)
R_ISET
ISET
(4)
I_SC = (3.3 - 1.85) / (11 x R_ISET)
CTRL
(6)
R
+
TO CLEAR
of
PWM LATCH
0.25 V
S1
OUT
ON
R
PWM
+
Cint
9.4 pF
OFF
Figure 32. UCD8220 Configured in Voltage Mode Control With an Internal Timing Capacitor
When the ISET resistor is configured as shown in Figure 32 with the ISET resistor connected between the ISET
pin and the 3V3 pin, the device is set up for voltage mode control. For purposes of voltage loop compensation
the, voltage ramp is 1.4 V from the valley to the peak. Use Equation 5 to calculate the proper resistance for a
desired clock frequency.
R_ISET =
(3.3 - 1.85) x 10
11 x 1.4 x fclk x 9.4
12
W
where
•
fclk = desired clock frequency in Hz
(5)
R_ISET Resistance − W
1M
100 k
10 k
1k
10
100
1000
10000
Clock Frequency − kHz
Figure 33. ISET Resistance Versus Clock Frequency
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Typical Application (continued)
Figure 33 shows the nominal value of resistance to use for a desired clock frequency. For example, a clock
frequency of 1000 kHz will require 10 kΩ of the ISET resistor. The UCD8220 device has two outputs controlled
by push-pull logic and therefore the output ripple frequency is equal to the clock frequency and each output
switches at half the clock frequency.
8.2.2.2 Selecting the ISET Resistor for Voltage Mode Control with Voltage Feed Forward
3V3
VIN
R_ISET
ISET
(4)
I_SC = (3.3 - 1.85) / (11 x R_ISET)
TO CLEAR
of
PWM LATCH
CTRL
(6)
R
0.25 V
S1
OUT
ON
R
+
PWM
+
Cint
9.4 pF
OFF
Figure 34. UCD8220 Configured in Voltage Mode Control with Voltage Feed Forward
When the ISET resistor is configured as shown in Figure 34 with the ISET resistor connected between the ISET
pin and the input voltage, VIN, the device is configured for voltage mode control with voltage feed forward. For
the purposes of voltage loop compensation, the voltage ramp is 1.4 V × VIN / VIN_max from the valley to the
peak. Use Equation 6 to calculate the proper resistance for a desired clock frequency and input voltage range.
R_ISET =
(Vin_max - 1.85) x 10
11 x 1.4 x fclk x 9.4
12
W
where
•
fclk = Desired Clock Frequency in Hz
(6)
For a general discussion of the benefits of voltage mode control with voltage feed forward, see (5) in the Related
Documentation section.
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Typical Application (continued)
8.2.2.3 Selecting the ISET Resistor for Peak Current Mode Control with Internal Slope Compensation
3V3
ISET
(4)
I_SC = 1.85 / (11 x R_ISET)
R_ISET
R
PWM
+
+
R
0.25 V
S1
OUT
ON
CTRL
(6)
-
TO CLEAR
of
PWM LATCH
Cint
12 pF
OFF
CS
(9)
S2
Figure 35. UCD8220 Configured in Peak Current Control with Internal Slope Compensation
When the ISET resistor is configured as shown in Figure 35 with the ISET resistor connected between the ISET
pin and the AGND pin, the device is configured for peak current-mode control with internal slope compensation.
The voltage at the ISET pin is 1.85 V so the internal slope compensation current, I_SC, being fed into the
internal slope compensation capacitor is equal to 1.85 / (11 × R_ISET). Use Equation 7 to calculate the voltage
slope at the PWM comparator input which is generated by this current.
6
SLOPE =
1.85 x 10
V/ms
11 x R_ISET x 12
(7)
RISET − Slope − V/µs
10.0
1.0
0.1
0.01
103
104
105
106
RISET − Resistance − Ω
Figure 36. Slope vs R_ISET Resistance
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Typical Application (continued)
The amount of slope compensation required depends on the design of the power stage and the output
specifications. A general rule is to add an up-slope equal to the down slope of the output inductor. Refer to (1)
and (8) in the Related Documentation section for a more detailed discussion regarding slope compensation in
peak current mode controlled power stages.
8.2.3 Application Curves
VDD (2 V/div)
VDD (2 V/div)
3V3 (2 V/div)
3V3 (2 V/div)
OUTx (2 V/div)
OUTx (2 V/div)
Time − 40 ms/div
Time − 40 ms/div
CLK = CTRL = 3V3
CLK = CTRL = 3V3
Figure 37. Start-Up Behavior at VDD = 12 V
Figure 38. Shut-Down Behavior at VDD = 12 V
VDD (2 V/div)
VDD (2 V/div)
3V3 (2 V/div)
3V3 (2 V/div)
OUTx (2 V/div)
OUTx (2 V/div)
Time − 40 ms/div
Time − 40 ms/div
CLK = AGND
CLK = AGND
CTRL = 3V3
Figure 39. Start-Up Behavior at VDD = 12 V
CTRL = 3V3
Figure 40. Shut-Down Behavior at VDD = 12 V
9 Power Supply Recommendations
The UCD8220 device operates from an input supply voltage range from 4.5 V to 15.5 V. Ensure that the power
supply rail is clean and uses high quality ceramic decoupling capacitors.
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10 Layout
10.1 Layout Guidelines
In a MOSFET driver operating at high frequency, minimizing stray inductance to minimize overshoot, undershoot,
and ringing is critical. The low output impedance of the drivers produces waveforms with high di/dt which tends to
induce ringing in the parasitic inductances. Connecting the driver device close to the MOSFETs is advantageous.
To reduce ringing, minimize the trace inductance from OUT 1 and OUT 2 to the MOSFET input. Connecting the
PGND and AGND pins to the PowerPAD integrated circuit package with a thin trace is recommended. Ensuring
that the voltage potential between these two pins does not exceed 0.3 V is critical. The use of schottky diodes on
the outputs to the PGND and PVDD pins is recommended when driving gate transformers. See (3) in the Related
Documentation section for a description of proper pad layout for the PowerPAD integrated circuit package.
10.2 Layout Example
Figure 41. UCD8220 Layout Example
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10.3 Thermal Considerations
The useful range of a driver is greatly affected by the drive power requirements of the load and the thermal
characteristics of the device package. In order for a power driver to be useful over a particular temperature range
the package must allow for the efficient removal of the heat produced while keeping the junction temperature
within rated limits. The UCD8220 device is available in the PowerPAD integrated circuit package, HTSSOP, to
cover a range of application requirements. The package has an exposed pad to enhance thermal conductivity
from the semiconductor junction.
As shown in (4) in the Related Documentation section, the PowerPAD integrated circuit packages offer a
leadframe die pad that is exposed at the base of the package. This pad is soldered to the copper on the PC
board (PCB) directly underneath the device package, reducing the RθJA down to 37.47°C/W. The PC board must
be designed with thermal lands and thermal vias to complete the heat removal subsystem, as discussed in (3) in
the Related Documentation section.
Note that the PowerPAD integrated circuit package is not directly connected to any leads of the package.
However, the PowerPAD is electrically and thermally connected to the substrate which is the ground of the
device. The PowerPAD integrated circuit package should be connected to the quiet ground of the circuit.
11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Modeling, Analysis and Compensation of the Current-Mode Converter, SLUA101
MSP430F1232, MSP430x11x2, MSP430x12x2 MIXED SIGNAL MICROCONTROLLER, SLAS361
PowerPAD Made Easy, SLMA004
PowerPAD Thermally Enhanced Package, SLMA002
Power Supply Seminar SEM-300 Topic 2, Closing the Feedback Loop, SLUP068
Power Supply Seminar SEM−1400 Topic 2: Design And Application Guide For High Speed MOSFET Gate Drive Circuits, SLUP133
Power Supply Seminar SEM-1600 Topic 6: A Practical Introduction to Digital Power Supply Control, SLUP224
Practical Considerations in Current Mode Power Supplies, SLUA110
11.2 Trademarks
TMS320, TrueDrive, PowerPAD are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
UCD8220PWP
ACTIVE
HTSSOP
PWP
16
90
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 105
UCD8220
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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