Texas Instruments TPS40200 User Manual
User's Guide
SLVU147A – February 2006 – Revised March 2006
Using the TPS40200
The TPS40200EVM-001 evaluation module (EVM) uses the TPS40200
nonsynchronous buck converter to provide a resistor-selected 3.3-V output voltage that
delivers up to 2.5 A from a 12-V input bus. The EVM operates from a single supply and
uses a single P-channel power FET and Schottky diode to produce a low-cost buck
converter. The part operates at a 300-kHz clock frequency with provision for external
frequency synchronization.
Contents
1 Description ........................................................................................... 2
2 TPS40200EVM-001 Electrical and Performance Specifications ............................. 2
3 Schematic ........................................................................................... 3
4 Test Setup ........................................................................................... 4
5 TPS40200EVM Typical Performance Data and Characteristic Curves ..................... 7
6 EVM Assembly Drawings and Layout ........................................................... 9
7 List of Materials .................................................................................... 14
List of Figures
1 TPS40200EVM-001 Schematic ................................................................... 3
2 TPS40200 Synchronized to a 50% Duty Cycle External Clock .............................. 4
3 TPS40200EVM-001 Recommended Test Setup ............................................... 6
4 Output Ripple Measurement - Tip and Barrel Using TP14 and TP15 ....................... 6
5 TPS40200EVM-001 Efficiency .................................................................... 7
6 TPS40200EVM-001 Efficiency .................................................................... 8
7 TPS40200EVM-001 Line and Load Regulation – Vout = 3.3255 V .......................... 8
8 TPS40200EVM-001 Line and Load Regulation – Vout = 5.0665 V ......................... 9
9 TPS40200EVM-001 Component Placement (Viewed from Top) ........................... 10
10 TPS40200EVM-001 Silkscreen (Viewed from Top) .......................................... 11
11 TPS40200EVM-001 Top View .................................................................. 12
12 TPS40200EVM-001 Bottom View ............................................................... 13
1 Adjusting V
2 TPS40200EVM-001 Bill of Materials ........................................................... 14
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OUT
List of Tables
With R6 Rounded to Standard 1% Resistor Values ......................... 3
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Description
1 Description
TPS40200EVM-001 is designed to operate with an 8-V to 16-V input and to produce a regulated 3.3-V
output with a load current from 0.125 A to 2.5 A. The TPS40200EVM-001 demonstrates the use of the
TPS40200 in a typical buck converter application. The board sacrifices some packing density to provide
ample test points for module evaluation. This EVM can be modified to support output voltages from 0.7 V
to 5 V by changing a single feedback resistor. The TPS40200EVM-001 has been built to the sample
application as described in the Application Information section of the TPS40200 data sheet (SLUS659 ).
1.1 Features
• 8-V to 16-V input range
• 3.3-V output, adjustable with single feedback resistor
• 0.125-A to 2.5-A steady-state output current
• 300-kHz switching frequency
• Single P-channel MOSFET and single rectifier
• Two-layer, 1.4-inch × 2.12-inch, surface-mount design with all components on one side
• Convenient test points for probing critical waveforms and noninvasive loop response testing
1.2 Applications
• Nonisolated medium-current, point-of-load and low-voltage bus converters
• Scanners
• Industrial controls
• Distributed power systems
• DSL/cable modems
2 TPS40200EVM-001 Electrical and Performance Specifications
PARAMETER TEXT CONDITIONS MIN NOM MAX UNIT
V
V
V
V
V
V
I
OUT
I
SCP
F
(1)
Input voltage 8 12 16 V
IN
Output voltage IOUT at 2.5 A, R6 = 26.7 k Ω 3.200 3.3 3.400
OUT
Line regulation ± 0.2% Vout 3.293 3.3 3.307 V
Load regulation ± 0.2% Vout 3.293 3.3 3.307 V
Output voltage IOUT at 2.5 A, R6 = 16.5 k Ω 4.85 5 5.150
OUT
Line regulation ± 0.2% Vout 4.990 5 5.010 V
Load regulation ± 0.2% Vout 4.990 5 5.010 V
Output ripple voltage At maximum output current 60 mV
RIPPLE
Output overshoot For 2.375-A load transient 60 mV
OVER
Output undershoot For 2.375-A load transient 60 mV
UNDER
Output current 0.125 2.5 A
Short-circuit current trip point Imax +50% minimum 3.75 5 A
Efficiency At nominal input voltage and maximum output 90%
Switching frequency 300 kHz
S
Set-point accuracy depends on external resistor tolerance and the reference voltage. Line and load regulation values are
referenced to the nominal design output voltage.
current
(1)
V
(1)
V
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Notes
R6 =26.7k for 3.3 Vout, R6 = 16.2k for 5.0 Vout
+
+
D3 : Do not populate. SOT 23 Common Cathode Dual Schottky
V
vout
V
ref
1
R
10
R
6
Schematic
3 Schematic
NOTE: For reference only; see Table 2, Bill of Materials for specific values
Figure 1. TPS40200EVM-001 Schematic
3.1 Adjusting Output Voltage (R6 and R10)
The regulated output voltage can be adjusted within a limited range by changing the ground resistor in the
feedback resistor divider (R6 and R10). The output voltage is given by Equation 1 .
Where V
Table 1 contains common values for R6 to generate popular output voltages. TPS40200EVM-001 is stable
through these output voltages with the efficiency rising with output voltage.
= 0.700 V and R10 = 100 k Ω
REF
V
Table 1. Adjusting V
- Output Voltage (V) R6 - Feedback Resistor Divider
OUT
With R6 Rounded to
OUT
Standard 1% Resistor Values
5 16.2
3.3 26.7
2.5 39
2 53.6
1.8 63.4
1.5 86.6
1.2 140
(1)
(k Ω )
3.2 Using Remote Synchronizing (TP6)
The TPS40200EVM-001 board has a synchronizing circuit that uses TP6 as an input. A logic high at this
input turns on a small signal FET (Q1) whose drain is connected to the oscillator setting node (RC) on the
TPS40200. The switching of this transistor over-drives the ramp associated with the internal oscillator and
causes the PWM switching to follow the input clock frequency. For reliable operation, the external clock
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Test Setup
frequency should be 25% to 30% higher than the frequency set by R3 and C5. The BSS83 used in this
circuit has a low (1-pF) output capacitance; so, its presence does not load down the normal operation of
the RC pin. With the controller’s frequency set to a 300-kHz frequency, the module synchronizes to a
390-kHz external clock that has a 50% duty cycle. A shorting jack, J2, is provided to disconnect the
synchronizing circuit from the (RC) node.
The following scope picture (Figure 2 ) shows a 5-V input clock at the TP6 input operating at 390 kHz and
a 50% duty cycle. The switch node also shown in the picture is switching at the same frequency with a
12-V V
supply. The RC operating frequency of the TPS40200 is set by R3 and C5 to be 300 kHz.
CC
Figure 2. TPS40200 Synchronized to a 50% Duty Cycle External Clock
4 Test Setup
4.1 Equipment
4.1.1 Voltage Source
V
— The input voltage source (V
12V_IN
METERS
A1: 0-A to 5-A dc ammeter
V1: V
V2: V
4.1.2 Loads
LOAD1 — The output load (LOAD1) should be an electronic constant-current-mode load capable of 0
A-to-2.5 A dc at 1.5 V.
4.1.3 Recommended Wire Gauge
V
to J1 — The connection between the source voltage, V
12V_IN
as 3 A dc. The minimum recommended wire size is AWG 16 with the length of wire less than 4 feet (2 feet
input, 2 feet return).
, 0-V to 20-V voltmeter
12V_IN
3V3_OUT
0 V to 10-V voltmeter
) should be a 0-V to 20-V variable dc source capable of 5 A dc.
12V_IN
and J1 of HPA164 can carry as much
12V_IN
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J3 to LOAD1 (Power) — The power connection between J3 of HPA164 and LOAD1 can carry as much as
5 A dc. The minimum recommended wire size is 2x AWG 16, with the length of wire less than 4 feet (2
feet output, 2 feet return).
J3 to LOAD1 (Remote Sense) — If remote sense is used, the remote sense connection between J3 of
HPA164 and LOAD1 will carry less than 1 A dc. The minimum recommended wire size is AWG 22, with
the length of wire less and 4 feet (2 feet output, 2 feet return).
4.1.4 Oscilloscope
A 60-MHz or faster oscilloscope can be used to determine the ripple voltage on 3V3_OUT. The
oscilloscope should be set for 1-M Ω impedance, ac coupling, 1- µ s/division horizontal resolution,
20-mV/division vertical resolution for taking output ripple measurements. TP14 and TP15 can be used to
measure the output ripple voltage by placing the oscilloscope probe tip through TP14 and holding the
ground barrel to TP15 as shown in Figure 3 . For a hands-free approach, the loop in TP15 can be cut and
opened to cradle the probe barrel. Using a leaded ground connection may induce additional noise due to
the large ground loop area. Connect a short wire from the barrel of the scope probe to TP15 as necessary
to reach between TP14 and TP15.
4.2 Equipment Setup
Shown in Figure 3 is the basic test setup recommended to evaluate the TPS40200EVM-001. Note that
although the return for J1 and J3 are the same, the connections should remain separate as shown in
Figure 3 .
4.2.1 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. Electrostatic smock and
safety glasses should also be worn.
2. Prior to connecting the dc-input source, V
5 A maximum. Ensure that V
3. Connect the ammeter A1 (0-A to 5-A range) between V
4. Connect voltmeter V1 to TP1 and TP3 as shown in Figure 3 .
5. Connect LOAD1 to J3 as shown in Figure 1 . Set LOAD1 to constant current mode to sink 0 A dc
before V
6. Connect voltmeter, V2 across J3 pin 3 and J3 pin 2 as shown in Figure 3 .
7. Connect the oscilloscope probe to TP14 and TP15 as shown in Figure 4 .
Test Setup
, it is advisable to limit the source current from V
12V_IN
is initially set to 0 V and connected as shown in Figure 2 .
12V_IN
and J1 as shown in Figure 3 .
12V_IN
is applied.
12V_IN
to
12V_IN
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