Texas Instruments TPS40077 User manual

User’s Guide
TPS40077 Buck Controller Evaluation Module User's
Guide
ABSTRACT
The TPS40077EVM-001 evaluation module (EVM) is a synchronous buck converter providing a fixed 1.8-V
output at up to 10 A from a 12-V input bus. The EVM is designed to start up from a single supply; no additional
bias voltage is required for start-up. The TPS40077 reduced-pin count synchronous buck controller used in
the EVM employs predictive gate drive. This feature provides improved efficiency by eliminating shoot-through
switching current,and minimizing the reverse-conduction time of the synchronous rectifier FET.
Table of Contents
1 Introduction.............................................................................................................................................................................2
1.1 Description......................................................................................................................................................................... 2
1.2 Applications........................................................................................................................................................................2
1.3 Features............................................................................................................................................................................. 2
2 TPS40077EVM-001 Electrical Performance Specifications................................................................................................ 3
3 Schematic................................................................................................................................................................................4
3.1 Adjusting Output Voltage (R3 and R13).............................................................................................................................5
3.2 Disable (J3)........................................................................................................................................................................ 5
3.3 Test Set Up.........................................................................................................................................................................5
3.4 Equipment Setup................................................................................................................................................................6
3.5 Start-Up/Shut Down Procedure..........................................................................................................................................7
3.6 Control Loop Gain and Phase Measurement Procedure................................................................................................... 8
3.7 Equipment Shutdown......................................................................................................................................................... 8
4 TPS40077EVM Typical Performance Data and Characteristic Curves...............................................................................9
4.1 Efficiency............................................................................................................................................................................9
4.2 Line and Load Regulation.................................................................................................................................................. 9
4.3 Output Ripple................................................................................................................................................................... 10
4.4 Transient Response......................................................................................................................................................... 10
4.5 Bode Plot..........................................................................................................................................................................11
5 EVM Assembly Drawings and Layout.................................................................................................................................12
6 List of Materials.....................................................................................................................................................................14
7 Revision History................................................................................................................................................................... 14
Trademarks
All trademarks are the property of their respective owners.
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1 Introduction
1.1 Description
The TPS40077EVM-001 is designed to use a 12-V (8 V-to-16 V) bus to produce a high current, regulated 1.8-V
output at up to 10 A of load current. The TPS40077EVM-001 demonstrates the use of the TPS40077 in a typical
12-V bus to low-voltage application, while providing a number of test points to evaluate the performance of the
TPS40077. The EVM can be modified to support output voltages from 0.9 V to 3.3 V by changing a single
resistor.
1.2 Applications
• Non-isolated, medium-current point-of-load and low-voltage bus converters
• Networking equipment
• Telecommunications equipment
• DC-power distributed systems
1.3 Features
• 8-V to 16-V input range
• 1.8-V fixed output, adjustable with a single resistor
• 10-A DC steady-state output current
• 300-kHz switching frequency
• Single main switch N-channel MOSFET and single synchronous rectifier N-channel MOSFET
• Double-sided PCB with all components on top side
• Active converter uses less than 2.4 square inches – 1.0 inches × 2.4 inches
• Convenient test points for probing critical waveforms and non-invasive loop response testing
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2 TPS40077EVM-001 Electrical Performance Specifications
Table 2-1. TPS40077EVM-001 Electrical and Performance Specifications
PARAMETER NOTES AND CONDITIONS MIN NOM MAX UNITS
INPUT CHARACTERISTICS
VIN Input voltage 8 12 16 V
IIN Input current VIN = nom, IOUT = max 1.7 1.8 A
No-load input current VIN = nom, IOUT = 0A 80 100 mA
VIN_UVLO Input UVLO IOUT = min to max 5.4 6 6.6 V
VIN_ONV Input ONV IOUT = min to max 6.3 7 7.7 V
OUTPUT CHARACTERISTICS
VOUT Output voltage VIN = nom, IOUT = nom 1.75 1.8 1.85 V
Line regulation VIN = min to max, IOUT = nom 0.5%
Load regulation VIN = nom, IOUT = min to max 0.5%
Output ripple voltage VOUT_ripple VIN = nom, IOUT = max 40 mVpp
Output current IOUT VIN = min to max 0 5 10 A
Output overcurrent inception point IOCP VIN = nom, VOUT = VOUT – 5% 12.25 19.4 34 A
Transient response
ΔI Load step IOUT_max to 0.2 × IOUT _max 8 A
Load slew rate 1 A/μsec
Overshoot 300 mV
Settling time 0.1 msec
SYSTEMS CHARACTERISTICS
fSW Switching frequency 240 300 360 kHz
ηpk Peak efficiency VIN = nom, IOUT = min to max 90%
η Full-load efficiency VIN = nom, IOUT = max 89%
Top Operating temperature range VIN = min to max, IOUT = min to max –40 25 85 °C
MECHANICAL CHARACTERISTICS
W Dimensions (active area) Width 1 ins
L Length 2.4 ins
h Component height 0.41 ins
NOTE 1: Voltage accuracy effected by resistor tolerance.
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3 Schematic
For reference only. See Table 6-1 for specific values.
+
+
Figure 3-1. TPS40077EVM-001 Schematic
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3.1 Adjusting Output Voltage (R3 and R13)
The regulated output voltage can be adjusted within a limited range by changing the ground resistors in the
feedback resistor-divider (R3, R13).
Table 3-1 contains common values for R3 and R13 to generate popular output voltages. The
TPS40077EVM-001 is stable through these output voltages but the efficiency can suffer as the power stage
is optimized for the 1.8-V output.
Table 3-1. Adjusting VOUT With R3
VOUT R3 R13
1.2 V 9.53 kΩ 62.0 kΩ
1.5 V 5.36 kΩ 140 kΩ
1.8 V 4.42 kΩ 24.9 kΩ
2.5 V 2.37 kΩ 71.5 kΩ
3.3 V 1.60 kΩ 220 kΩ
3.2 Disable (J3)
The TPS40077EVM-001 provides a Disable input (J3) that allows the user to evaluate the Enable/Disable
function of the TPS40077. When a short is applied across the pins of J3, the TPS40077 controller is disabled
and the EVM shuts down. When the TPS40077 is disabled, both FET drivers are off.
3.3 Test Set Up
3.3.1 Equipment
3.3.1.1 Voltage Source
V12V_IN
The input voltage source (V12V_IN) should be a 0-V to 16-V variable DC source capable of 5 ADC. Connect
V12V_IN to J1 as shown in Figure 3-3.
3.3.1.2 Meters
• A1: 0-5 ADC, ammeter
• V1: V12V_IN, 0-V to 16-V voltmeter
• V2: V1V5_OUT 0-V to 5-V voltmeter
3.3.1.3 Loads
LOAD1
The output load (LOAD1) must be a constant-current mode electronic load capable of 0-A to 15-A DC at 1.8 V.
3.3.1.4 Oscilloscope
A digital or analog oscilloscope can be used to measure the ripple voltage on VOUT. The oscilloscope should be
set to the following to measure output ripple:
• 1-MΩ impedance
• 20-MHz bandwidth
• AC coupling
• 1-μs/division horizontal resolution
• 20-mV/division vertical resolution
TP9 and TP10 can be used to measure the output ripple voltage by placing the oscilloscope probe tip through
TP9 and holding the ground barrel to TP10 as shown in Figure 3-2. For a hands-free approach, the loop in TP10
can be cut and opened to cradle the probe barrel. Using a leaded ground connection must be avoided because it
induces additional noise due to its large ground-loop area.
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TP10TP9
Metal Ground Barrel
Probe Tip
Tip and Barrel Vout Ripple
Measurement
Figure 3-2. Output Ripple Measurement – Tip and Barrel Using TP9 and TP10
3.3.1.5 Recommended Wire Gauge
V12V_IN to J1
The connection between the source voltage, V12V_IN, and J1 can carry as much as 3 ADC. The minimum
recommended wire size is AWG #16 with the total length of wire less than four feet (2-feet input, 2-feet return).
J2 to LOAD1 (Power)
The power connection between J2 and LOAD1 can carry as much as 15 ADC. The minimum recommended wire
size is 2 × AWG #16, with the total length of wire less than four feet (2-feet output, 2-feet return).
3.4 Equipment Setup
Figure 3-3 shows the basic recommended test set up to evaluate the TPS40077EVM-001. Note that although
the return for J1 and J2 are the same, the connections should remain separate as shown in Figure 3-2.
3.4.1 Procedure
1. Working at an ESD workstation, make sure that any wrist straps, bootstraps, or mats are connected
referencing the user to earth ground before power is applied to the EVM. An electrostatic smock and safety
glasses should also be worn.
2. Prior to connecting the DC input source, V12V_IN, it is advisable to limit the source current from V12V_IN to
5.0-A maximum. Make sure V12V_IN is initially set to 0 V and connected as shown in Figure 3-3.
3. Connect an Ammeter A1 as shown in Figure 3-3.
4. Connect Voltmeter V1 to TP1 and TP2 as shown in Figure 3-3.
5. Connect LOAD1 to J2 as shown in Figure 3-3. Set LOAD1 to constant current mode to sink 0 A DC before
V12V_IN is applied.
6. Connect Voltmeter V2 to Output J2 as shown in Figure 3-3.
7. Connect an oscilloscope probe to TP9 and TP10 as shown in Figure 3-2.
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3.4.2 Diagram
.
Oscilloscope
1M!, AC
20MH
z
1.8V
0 to 10A
LOAD1
+ -
V2
+-
V1
+-
0 to 15V
V12V_IN
- +
A1
See figure 2 for tip
and barrel
measurement
Figure 3-3. TPS40077EVM-001 Recommended Test Setup
V1
+-
Network
Analyzer
0 to 15V
V12V_IN
- +
A1
CHA CHB
See section 3.7
1.8V
0 to 10A
LOAD1
+ -
V2
+-
Figure 3-4. Control Loop Measurement Setup
3.5 Start-Up/Shut Down Procedure
1. Increase V12V_IN from 0 VDC to 12 VDC.
2. Vary LOAD1 from 0 ADC–10 ADC.
3. Vary V12V_IN from 8 VDC to 16 VDC.
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4. Decrease LOAD1 to 0 A.
3.6 Control Loop Gain and Phase Measurement Procedure
1. Connect a 1-kHz to 1-MHz isolation transformer to TP3 and TP6 as shown in Figure 3-4.
2. Connect an .input-signal amplitude-measurement probe (channel A) to TP3 as shown in Figure 3-4
3. Connect an output-signal amplitude measurement probe (channel B) to TP6 as shown in Figure 3-4.
4. Connect the ground lead of channel A and channel B to TP8 as shown in Figure 3-4.
5. Inject 25-mV or less signal across TP3 and TP6 through an isolation transformer.
6. Sweep frequency from 1 kHz to 1 MHz with 10 Hz or lower post filter.
7. Control-loop gain can be measured by
20 LOGǒChannelB
ChannelAǓ
.
8. Control-loop phase is measured by the phase difference between channel A and channel B.
9. Disconnect an isolation transformer from TP3 and TP6 before making other measurements (signal injection
into feedback can interfere with accuracy of other measurements).
3.7 Equipment Shutdown
1. Shut down the oscilloscope.
2. Shut down LOAD1.
3. Shut down V12V_IN.
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4 TPS40077EVM Typical Performance Data and Characteristic Curves
Figure 4-1 through Figure 4-6 present typical performance curves for the TPS40077EVM-001. Since 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.
4.1 Efficiency
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8 9 10
I - Load Current - A
O
h- Efficiency - %
V = 8.0 V
IN
V = 16.0 V
IN
V = 12.0 V
IN
Figure 4-1. TPS40077EVM-001 Efficiency
4.2 Line and Load Regulation
1.750
1.770
1.790
1.810
1.830
1.850
0 1 2 3 4 5 6 7 8 9 10
I - Load Current - A
O
V - Output Voltage - V
O
V = 8.0 V
IN
V = 16.0 V
IN
V = 12.0 V
IN
Figure 4-2. TPS40077EVM-001 Line and Load Regulation
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4.3 Output Ripple
V = 12 V, V = 1.8 V, I = 10 A
IN OUT OUT
Figure 4-3. TPS40077EVM-001 Typical Output Ripple
4.4 Transient Response
Figure 8. Load Transient, 2A to 10A, slew rate = 1A/!s, VIN = 12V, VOUT = 1.8V
Slew rate = 1 A/ s, V = 12 V, V = 1.8 VmIN OUT
CH4 = IOUT
CH1 = VOUT
Figure 4-4. Load Transient, 2 A to 10 A
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