Texas Instruments LMR33640EVM User manual

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LMR33640EVM User's Guide
User's Guide
SNVU664–November 2019
LMR33640EVM User's Guide
The Texas Instruments LMR33640EVM evaluation module (EVM) helps designers evaluate the operation
and performance of the LMR33640 buck regulator. The LMR33640 is an easy-to-use synchronous step-
down DC/DC converters capable of driving up to 4 A of load current from an input voltage of 3.8 V to 36 V.
The LMR33640EVM features a selectable output voltage of 3.3 V or 5 V and a switching frequency of
either 400 kHz. See the LMR33640 SIMPLE SWITCHER 3.8-V to 36-V, 4-A Step-Down Converter Data
Sheet for additional features, detailed description, and available options.
Table 1 shows the EVM configuration.
Table 1. Device and Package Configurations
EVM DEVICE FREQUENCY/OUTPUT
CURRENT
LMR33640EVM LMR33640ADDA 400 kHz / 4 A
Figure 1. EVM Board Image

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LMR33640EVM User's Guide
Contents
1 Setup .......................................................................................................................... 3
2 Operation ..................................................................................................................... 5
3 Performance Curves ........................................................................................................ 6
4 Schematic..................................................................................................................... 7
5 Board Layout ................................................................................................................. 8
6 Bill of Materials ............................................................................................................. 11
List of Figures
1 EVM Board Image........................................................................................................... 1
2 EVM Board Connections.................................................................................................... 3
3 EVM Card Edge Connections.............................................................................................. 4
4 Jumper Locations............................................................................................................ 4
5 FRA Setup.................................................................................................................... 5
6 Efficiency: VIN = 12 V, VOUT = 5 V, ƒSW = 400 KHz..................................................................... 6
7 Efficiency: VIN = 12 V, VOUT = 3.3V, ƒSW = 400 kHz.................................................................... 6
8 LMR33640EVM Schematic................................................................................................. 7
9 Top View of EVM ............................................................................................................ 8
10 EVM Top Copper Layer..................................................................................................... 8
11 EVM Mid Layer One......................................................................................................... 9
12 EVM Mid Layer Two......................................................................................................... 9
13 EVM Bottom Copper Layer ............................................................................................... 10
List of Tables
1 Device and Package Configurations ...................................................................................... 1
2 BOM for LMR33640EVM.................................................................................................. 11
Trademarks
All trademarks are the property of their respective owners.

LOAD
INPUT
SUPPLY
(+)
DMM
(-)
DMM
(+)
(+)
(+)(-)
(-)
(-)
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LMR33640EVM User's Guide
1 Setup
This section describes the test points and connectors on the EVM and how to properly connect, set up,
and use the LMR33640EVM. Either the banana jacks and test points on the top of the board or the card
edge connector can be used for connections. See Figure 2 for the top of board connections and Figure 3
for the card edge connections. The following are the functions of the connections:
•VIN - Input supply to EVM. Connect to a suitable input supply. See the LMR33640 SIMPLE
SWITCHER 3.8-V to 36-V, 4-A Step-Down Converter Data Sheet for input supply requirements.
•GND - System ground
•VOUT - Output of EVM. Connect to desired load.
•VOS - Output voltage sense connection
•VIS - Input voltage sense connection
•GNDS - Ground sense point for analog measurements
Figure 2. EVM Board Connections

Enable
Jumper
VOUT Selection
Jumper
GND VOUT
GNDS
VOS
TOP FRONT
BOTTOM FRONT
VIS
VIN
INPUT
SUPPLY LOAD
(+) (-) (-) (+)
(+)(-)
DMMDMM
(-)(+)
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Figure 3. EVM Card Edge Connections
1.1 Jumpers
See Figure 4 for jumper locations.
•EN - This jumper allows the EN input to be connected to either ground (OFF) or VIN (ON). Remove
this jumper to allow an external logic signal to control the EN function.
•VOUT - This jumper is used to select one of the two pre-defined output voltages. The "3.3V" position
provides a 3.3 V output while the "5V" position provides a 5 V output.
Figure 4. Jumper Locations
1.2 Test Points
•VIN - Input supply to EVM. Connect to a suitable input supply. See the LMR33640 SIMPLE
SWITCHER 3.8-V to 36-V, 4-A Step-Down Converter Data Sheet for input supply requirements.
•GND - System power ground

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•VOUT - Power output of EVM. Connect to desired load.
•VOS - Output voltage sense connection. Connect to DMM. This is also used for frequency response
analyzer connection.
•VIS - Input voltage sense connection. Connect to DMM.
•GNDS - Ground sense point for analog measurements. Connect to DMM.
•VCC - Test point to measure internal VCC of device; approximately 5 V. An on-board PGOOD pullup
resistor is connected to VCC.
•EN - Connection for external EN logic input. Remove EN jumper and connect controlling logic to EN
test point for external enable control.
•PGOOD - Power-good flag output. This test point is connected to VCC through a 20 kΩresistor. The
power good function can be monitored at this test point.
•A - Connection for frequency response analyzer (on bottom of board). See Figure 5.
Figure 5. FRA Setup
2 Operation
Once the previously described connections are made and the appropriate jumpers are set, the EVM is
ready to use. If external control of the EN input is desired, remove the EN jumper and apply the external
signal to the EN test point and GND. The PGOOD output is pulled up to VCC through a 20-kΩresistor.
This way, the PGOOD signal swings from 0 V to about 5 V to indicate when the output voltage is either
outside or inside of the PGOOD window, respectively. If an external pullup and supply is desired for the
PGOOD function, remove the 20-kΩresistor and pull the PGOOD test point up to the desired voltage
through an appropriate resistance. See the LMR33640 SIMPLE SWITCHER 3.8-V to 36-V, 4-A Step-
Down Converter Data Sheet for more details.

Output Current (A)
Efficiency (%)
0.001 0.01 0.1 1 55
50
55
60
65
70
75
80
85
90
95
100
eff_
8V
12V
24V
36V
Output Current (A)
Efficiency (%)
0.001 0.01 0.1 1 55
45
50
55
60
65
70
75
80
85
90
95
100
eff_
8V
12V
24V
36V
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The output voltage of the EVM can be selected by the VOUT jumper to either 3.3 V or 5 V. Other values
of output voltage can be programmed by changing the value of RFBB on the EVM. In addition, the values of
the inductor and the output capacitance may also need to be changed. See the LMR33640 SIMPLE
SWITCHER 3.8-V to 36-V, 4-A Step-Down Converter Data Sheet for more information.
The EVM has been designed for maximum flexibility regarding component selection. This allows the user
to place preferred components, such as the inductor and capacitors, on the board and test the
performance of the regulator. The power supply system can be tested before committing the design to
production.
3 Performance Curves
Figure 6. Efficiency: VIN = 12 V, VOUT = 5 V, ƒSW = 400 KHz Figure 7. Efficiency: VIN = 12 V, VOUT = 3.3V, ƒSW = 400 kHz

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4 Schematic
Figure 8. LMR33640EVM Schematic

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5 Board Layout
Figure 9. Top View of EVM
Figure 10. EVM Top Copper Layer

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Figure 11. EVM Mid Layer One
Figure 12. EVM Mid Layer Two

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Figure 13. EVM Bottom Copper Layer