Texas Instruments TPS56221EVM-579 User manual

User's Guide
SLVU446–March 2011
TPS56221EVM-579 Evaluation Module
The Texas Instruments TPS56221EVM-579 evaluation module (EVM) is a synchronous buck converter
providing a fixed 1.2-V output at up to 25 A from a 12-V input bus. The EVM is designed to start up from a
single supply; so, no additional bias voltage is required for start-up. The module uses the TPS56221
High-Current, Synchronous Buck Converter with integrated MOSFETs.
The TPS56221 integrates TI’s high-performance controller technology with TI’s industry-leading MOSFET
technology in a standard QFN package to meet the demands of modern, high-current, space-constrained
applications.
Contents
1 Introduction .................................................................................................................. 3
1.1 Description .......................................................................................................... 3
1.2 Applications ......................................................................................................... 3
1.3 Features ............................................................................................................. 3
2 TPS56221EVM-579 Electrical Performance Specifications ........................................................... 3
3 TPS56221EVM-579 Schematic ........................................................................................... 4
4 Connector and Test Point Descriptions .................................................................................. 5
4.1 Enable/SS Test Point – TP5 ...................................................................................... 5
4.2 Test Point Descriptions ............................................................................................ 5
5 Test Setup ................................................................................................................... 6
5.1 Equipment ........................................................................................................... 6
5.2 Equipment Setup ................................................................................................... 7
5.3 Start-Up/Shutdown Procedure ................................................................................... 9
5.4 Output Ripple Voltage Measurement Procedure .............................................................. 9
5.5 Control Loop Gain and Phase Measurement Procedure .................................................... 10
5.6 Equipment Shutdown ............................................................................................ 10
6 TPS56221EVM-579 Test Data .......................................................................................... 10
6.1 Efficiency .......................................................................................................... 10
6.2 Line and Load Regulation ....................................................................................... 11
6.3 Output Voltage Ripple ........................................................................................... 11
6.4 Switch Node ....................................................................................................... 12
6.5 Control Loop Bode Diagram .................................................................................... 12
7 TPS56221EVM-579 Assembly Drawings and Layout ................................................................ 13
8 TPS56221EVM-579 Bill of Materials .................................................................................... 19
List of Figures
1 TPS56221EVM-579 Schematic........................................................................................... 4
2 TPS56221EVM-579 Recommended Test Setup ....................................................................... 8
3 Output Ripple Measurement – Tip and Barrel Using TP3 and TP4.................................................. 8
4 Control Loop Measurement Setup........................................................................................ 9
5 TPS56221EVM-579 Efficiency vs Load Current ...................................................................... 10
6 TPS56221EVM-579 Output Voltage vs Load Current................................................................ 11
7 TPS56221EVM-579 Output Voltage Ripple............................................................................ 11
8 TPS56221EVM-579 Switching Waveform.............................................................................. 12
9 TPS56221EVM-579 Gain and Phase vs Frequency.................................................................. 12
1
SLVU446–March 2011 TPS56221EVM-579 Evaluation Module
Submit Documentation Feedback © 2011, Texas Instruments Incorporated

www.ti.com
10 TPS56221EVM-579 Component Placement, Viewed From Top.................................................... 13
11 TPS56221EVM-579 Silk Screen, Viewed From Top ................................................................. 14
12 TPS56221EVM-579 Top Copper, Viewed From Top................................................................. 15
13 TPS56221EVM-579 Bottom Copper, Viewed From Bottom......................................................... 16
14 TPS56221EVM-579 Internal 1, X-Ray Viewed From Top............................................................ 17
15 TPS56221EVM-579 Internal 2, X-Ray Viewed From Top............................................................ 18
List of Tables
1 TPS56221EVM-579 Electrical and Performance Specifications...................................................... 3
2 Test Point Descriptions..................................................................................................... 5
3 TPS56221EVM-579 Bill of Materials.................................................................................... 19
2TPS56221EVM-579 Evaluation Module SLVU446–March 2011
Submit Documentation Feedback
© 2011, Texas Instruments Incorporated

www.ti.com Introduction
1 Introduction
1.1 Description
TPS56221EVM-579 is designed to use a regulated 12-V (8-V to 14-V) bus voltage to provide a regulated
1.2-V output at up to 25 A of load current. TPS56221EVM-579 is designed to demonstrate the TPS56221
high-current integrated, FET converter in a typical space-limited 12-V bus to low-voltage point-of-load
application.
1.2 Applications
• High-current, low-voltage FPGA or microcontroller core supplies
• High-current, point-of-load modules
• Telecommunications equipment
• Computer peripherals
1.3 Features
• 8-V to 14-V input voltage rating
• 1.2-V ±2% output voltage rating
• Less than 400-mm2active PCB area (excluding bulk input and output capacitors)
• 25-A steady-state load current
• 500-kHz switching frequency
• Simple access to IC features including Power Good, Enable, Soft-Start, and Error Amplifier
• Convenient test points for simple, non-invasive measurements of converter performance.
2 TPS56221EVM-579 Electrical Performance Specifications
Table 1. TPS56221EVM-579 Electrical and Performance Specifications
Parameter Notes and Conditions Min Typ Max Unit
Input Characteristics
VIN Input voltage 8 12 14 V
IIN Input current VIN = 12 V, IOUT = 25 A – 2.8 3.2 A
No-load input current VIN = 12 V, IOUT = 0 A – 35 50 mA
VIN_UVLO Input UVLO IOUT = 10 A 4.2 V
Output Characteristics
VOUT1 Output Voltage 1 VIN = 12 V, IOUT = 12 A 1.17 1.2 1.23 V
Line regulation VIN = 8 V to 14 V – – 0.5%
Load regulation IOUT = 0 A to 25 A – – 1%
VOUT_ripple Output voltage ripple VIN = 12, IOUT = 25 – – 24 mVpp
IOUT1 Output Current 1 VIN = 8 to 14 0 25 A
Systems Characteristics
FSW Switching frequency 450 500 550 kHz
ηpk Peak efficiency VIN = 12 V, IOUT = 12 A – 92% –
ηFull-load efficiency VIN = 12 V, IOUT = 25 A – 89% –
3
SLVU446–March 2011 TPS56221EVM-579 Evaluation Module
Submit Documentation Feedback © 2011, Texas Instruments Incorporated

+
TPS56221EVM-579 Schematic www.ti.com
3 TPS56221EVM-579 Schematic
NOTE: For Reference Only, See Table 3.
Figure 1. TPS56221EVM-579 Schematic
4TPS56221EVM-579 Evaluation Module SLVU446–March 2011
Submit Documentation Feedback
© 2011, Texas Instruments Incorporated

www.ti.com Connector and Test Point Descriptions
4 Connector and Test Point Descriptions
4.1 Enable/SS Test Point – TP5
TPS56221EVM-579 is designed with a test point at the Enable/Soft-Start point (TP5). Shorting TP5 to
GND connects the EN/SS pin to GND, discharges the soft-start capacitor, and disables the TPS56221
converter. This forces the output into a high-impedance state (approximately 40 kΩto GND).
4.2 Test Point Descriptions
Table 2. Test Point Descriptions
Test Point Label Use Section
TP1 VIN Measurement Test Point for Input Voltage Section 4.2.1
TP2 GND Ground Test Point for Input Voltage Section 4.2.1
TP3 VOUT Measurement Test Point for Output Voltage Section 4.2.2
TP4 GND Ground Test Point for Output Voltage Section 4.2.2
TP5 Enable Measurement Test Point for Enable/Soft-Start Section 4.2.3
TP6 Power Measurement Test Point for Power Good Section 4.2.4
Good
TP7 CHA Measurement Test Point for Channel A of Loop Response Section 4.2.5
TP8 SGND Ground Test Point for Channel A of Loop Response Section 4.2.5
TP9 SGND Ground Test Point for Channel A of Loop Response Section 4.2.5
TP10 CHB Measurement Test Point for Channel B of Loop Response Section 4.2.5
4.2.1 Input Voltage Monitoring – TP1 and TP2
The TPS56221EVM-579 provides two test points for measuring the input voltage applied to the module.
This allows the user to measure the actual input module voltage without losses from input cables and
connectors. All input voltage measurements should be made between TP1 and TP2. To use TP1 and
TP2, connect a voltmeter positive input to TP1 and input terminal to TP2.
4.2.2 Output Voltage Monitoring – TP3 and TP4
The TPS56221EVM-579 provides two test points for measuring the output voltage generated by the
module. This allows the user to measure the actual module output voltage without losses from input
cables and connectors. All input voltage measurements should be made between TP3 and TP4. To use
TP3 and TP4, connect a voltmeter positive input to TP3 and negative input to TP4.
4.2.3 Enable/Soft-Start Monitoring – TP5
The TPS56221EVM-579 provides a test point for measuring the Enable/Soft-Start voltage of the
TPS56221 converter. This test point can be externally shorted to GND to disable the TPS56221 controller
or monitored to observe the start-up calibration waveform, soft-start ramp, or fault time-out timing.
The Enable/Soft-Start test point can be externally shorted to GND but must not be actively driven from an
external circuit, such as a logic output of another power supply.
4.2.4 Power Good Monitoring – TP6
The TPS56221EVM-579 provides a test point for connecting the Power Good output of the TPS56221
converter with an external circuit. To maintain compatibility with the TPS56221EVM-579 Enable/Soft-Start
testing point and allow two TPS56221EVM-579 modules to be easily sequenced, the Power Good test
point does not include an onboard pullup resistor.
When connecting to another TPS56221EVM-579 module, the Power Good test point (TP6) of one module
can be directly connected to the Enable/Soft-Start test point (TP5) of a second module to provide simple
sequential start-up sequencing.
5
SLVU446–March 2011 TPS56221EVM-579 Evaluation Module
Submit Documentation Feedback © 2011, Texas Instruments Incorporated

Test Setup www.ti.com
If the Power Good test point must be connected to an external logic circuit or monitored for power-on
sequence testing, an external pullup may be required.
4.2.5 Loop Response Testing – TP7, TP8, TP8, TP10, and R5
The TPS56221EVM-579 provides four test points (two signal and two ground) for measuring the control
loop frequency response. This allows the user to measure the actual module loop response without
modifying the evaluation board. A transformer-isolated signal up to 30 mV can be injected between TP7
and TP10. The injected signal amplitude can be measured by the ac-coupled amplitude at CHA (TP7),
and the resulting output voltage deviation can be measured at CHB (TP10). See Figure 4 for additional
detail.
5 Test Setup
5.1 Equipment
5.1.1 Voltage Source
VIN:The input voltage source (VIN) must be a 0-V to 15-V variable dc source capable of supplying 3.5 Adc.
5.1.2 Meters
A1: Input current meter. 0-Adc to 5-Adc ammeter
V1: Input voltage meter. 0-V to 15-V voltmeter
V2: Output voltage meter. 0-V TO 2-V voltmeter
5.1.3 Loads
LOAD1: Output load. Electronic load set for constant current or constant resistance capable of 0-Adc to
25-Adc at 1.2 Vdc
5.1.4 Oscilloscope
For Output Voltage Ripple: Oscilloscope must be an analog or digital oscilloscope set for ac-coupled
measurement with 20-MHz bandwidth limiting. Use 20-mV/division vertical resolution, 1-µs/division
horizontal resolution.
For Switching Waveforms: Oscilloscope must be an analog or digital oscilloscope set for dc-coupled
measurement with 20-MHz bandwidth limiting. Use 2-V/division or 5-V/division vertical resolution and
1-µs/division horizontal resolution.
5.1.5 Recommended Wire Gauge
VIN to J1
The connection between the source voltage (VIN) and J1 of TPS56221EVM-579 can carry as much as 3.5
Adc of current. The minimum recommended wire size is AWG 16 with the total length of wire less than 2
feet (1-foot input, 1- foot return)
J2 to LOAD1
The connection between the source voltage (VIN) and J1 of TPS56221EVM-579 can carry as much as 25
Adc of current. The minimum recommended wire size is 2x AWG 14 with the total length of wire less than
2 feet (1-foot input, 1-foot return).
NOTE: J2 is a 4 position terminal jack using positions for each VOUT and GND. Each position is rated to
support 15A of output current. When delivering more than 15A of current, both VOUT and both GND
positions should be used.
6TPS56221EVM-579 Evaluation Module SLVU446–March 2011
Submit Documentation Feedback
© 2011, Texas Instruments Incorporated

www.ti.com Test Setup
5.1.6 Thermal
FAN
The TPS56221EVM-579 evaluation module includes components that can become hot to the touch when
operating. Because this evaluation module is not enclosed to allow probing of circuit nodes, a small fan
capable of 200-400 lfm is recommended to reduce component temperatures when operating.
5.2 Equipment Setup
Shown in Figure 2 is the basic test setup recommended to evaluate the TPS56221EVM-579. Note that
although the return for J1 and JP2 are the same system ground, the connections must remain separate as
shown in Figure 2.
5.2.1 Procedure
1. Working at an ESD workstation, ensure that any wrist straps, bootstraps, or mats are connected
referencing the user to earth ground before power is applied to the EVM. Wearing an electrostatic
smock and safety glasses is also recommended.
2. Prior to connecting the dc input source, VIN, it is advisable to limit the source current from VIN to 4 A
maximum. Ensure that VIN is initially set to 0 V and connected as shown in Figure 2.
3. Connect VIN to J1 as shown in Figure 2.
4. Connect ammeter A1 between VIN and J1 as shown in Figure 2.
5. Connect voltmeter V1 to TP1 and TP2 as shown in Figure 2.
6. Connect voltmeter V2 to TP3 and TP4 as shown in Figure 2.
7. Connect Oscilloscope Probes to desired test points per Table 2.
8. Locate the fan as shown in Figure 2 and turn it on, ensuring that the air blows directly across the
evaluation module.
7
SLVU446–March 2011 TPS56221EVM-579 Evaluation Module
Submit Documentation Feedback © 2011, Texas Instruments Incorporated

LOAD1
1.2V @
25A
-
+
FAN
V2
-
+
See Tip and Barrel
Measurement for
Vout ripple
Oscilloscope
1MW, AC
20mV / div
20MHz
A1
-
+
V
VIN
V1
-
+
TP4TP3
Metal Ground Barrel
Probe Tip
Tip and Barrel Vout ripple
measurement
Test Setup www.ti.com
5.2.2 Diagram
Figure 2. TPS56221EVM-579 Recommended Test Setup
Figure 3. Output Ripple Measurement – Tip and Barrel Using TP3 and TP4
8TPS56221EVM-579 Evaluation Module SLVU446–March 2011
Submit Documentation Feedback
© 2011, Texas Instruments Incorporated

FAN
LOAD1
1.2V @
25A
-
+
V2
-
+
See Tip and Barrel
Measurement for
Vout ripple
Oscilloscope
1MW, AC
20mV / div
20MHz
A1
-
+
V
VIN
V1
-
+
Network
Analyzer
Isolation
Transformer
www.ti.com Test Setup
Figure 4. Control Loop Measurement Setup
5.3 Start-Up/Shutdown Procedure
1. Increase VIN from 0 Vdc to 12 Vdc.
2. Vary LOAD1 from 0 Adc to 25 Adc.
3. Vary VIN from 8 V to 14 V.
4. Decrease VIN to 0 V.
5. Decrease LOAD1 to 0 A.
5.4 Output Ripple Voltage Measurement Procedure
1. Follow Section 5.3 Steps 1-5 to set VIN and LOAD1 to desired operating condition
2. Connect Oscilloscope Probe with exposed metal barrel to TP3 and TP4 per Figure 3
3. Set oscilloscope per Oscilloscope For Output Voltage Ripple measurement in Section 5.1.4.
4. Follow Steps 4 and 5 in Section 5.3 to power down.
9
SLVU446–March 2011 TPS56221EVM-579 Evaluation Module
Submit Documentation Feedback © 2011, Texas Instruments Incorporated

æ ö
´ç ÷
è ø
ChannelB
20 LOG
ChannelA
70
75
80
85
90
95
0 5 10 15 20 25
h- Efficiency - %
I - Load Current - A
LOAD
V = 8 V
IN
V = 12 V
IN
V = 14 V
IN
V = 12 V,
V = 1.2 V,
I = 0-25 A
IN
OUT
OUT
TPS56221EVM-579 Test Data www.ti.com
5.5 Control Loop Gain and Phase Measurement Procedure
1. Follow Steps 1-5 in Section 5.3 to set Vin and LOAD1 to desired operating condition.
2. Connect a 1-kHz to 1-MHz isolation transformer to TP5 and TP7 as shown in Figure 4.
3. Connect input signal amplitude measurement probe (Channel A) to TP7 as shown in Figure 4.
4. Connect output signal amplitude measurement probe (Channel B) to TP5 as shown in Figure 4.
5. Connect ground lead of Channel A and Channel B to TP6 and TP8 as shown in Figure 4.
6. Inject a 30-mV or less signal across R3 through the isolation transformer.
7. Sweep the frequency from 1 kHz to 1 MHz with a 10-Hz or lower post filter.
8. The control loop gain can be measured by
9. The control loop phase can be measured by the phase difference between Channel A and Channel B.
10. Follow Steps 4 and 5 in Section 5.3 to power down.
5.6 Equipment Shutdown
1. Shut down oscilloscope.
2. Shut down LOAD1.
3. Shut down VIN.
4. Shut down fan.
6 TPS56221EVM-579 Test Data
Figure 5 through Figure 8 present typical performance curves for the TPS56221EVM-579. Because actual
performance data can be affected by measurement techniques and environmental variables, these curves
are presented for reference and may differ from actual field measurements.
6.1 Efficiency
Figure 5. TPS56221EVM-579 Efficiency vs Load Current
10 TPS56221EVM-579 Evaluation Module SLVU446–March 2011
Submit Documentation Feedback
© 2011, Texas Instruments Incorporated