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TPS54227
SLVSAU2C – MAY 2011 – REVISED DECEMBER 2015
TPS54227 4.5-V to 18-V Input, 2-A Synchronous Step-Down Converter
1 Features
3 Description
•
The TPS54227 device is an adaptive ON-time DCAP2 mode synchronous buck converter. The
TPS54227 enables system designers to complete the
bus regulators for a suite of various end equipment
with a cost-effective, low component count, low
standby current solution. The main control loop for
the TPS54227 uses the D-CAP2 mode control which
provides a fast transient response with no external
compensation components. The TPS54227 also has
a proprietary circuit that enables the device to adopt
to both low equivalent series resistance (ESR) output
capacitors, such as POSCAP or SP-CAP, and ultralow ESR ceramic capacitors. The device operates
from 4.5-V to 18-V VIN input. The output voltage can
be programmed between 0.76 V and 7 V. The device
also features an adjustable soft-start time. The
TPS54227 is available in the 8-pin HSOP package
and 10-pin VSON, and is designed to operate from
–40°C to 85°C.
1
•
•
•
•
•
•
•
•
•
•
D-CAP2™ Mode Enables Fast Transient
Response
Low Output Ripple and Allows Ceramic Output
Capacitor
Wide VIN Input Voltage Range: 4.5 V to 18 V
Output Voltage Range: 0.76 V to 7 V
Highly-Efficient Integrated FETs Optimized
for Lower Duty Cycle Applications
– 155 mΩ (High-Side) and 108 mΩ (Low-Side)
High Efficiency, Less Than 10 μA at Shutdown
High Initial Bandgap Reference Accuracy
Adjustable Soft-Start
Prebiased Soft-Start
700-kHz Switching Frequency (fSW)
Cycle-By-Cycle Overcurrent Limit
2 Applications
•
Device Information(1)
Wide Range of Applications for Low-Voltage
System
– Digital TV Power Supply
– High-Definition Blu-ray Disc™ Players
– Networking Home Terminals
– Digital Set Top Boxes (STB)
Simplified Schematic
TPS54227DDA
PART NUMBER
TPS54227
PACKAGE
BODY SIZE (NOM)
SO PowerPAD (8)
4.89 mm × 3.90 mm
VSON (10)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
TPS54227 Transient Response
Vout (50 mV/div)
Iout (1 A/div)
100 ms/div
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.
TPS54227
SLVSAU2C – MAY 2011 – REVISED DECEMBER 2015
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
4
4
4
5
5
6
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 8
7.1 Overview ................................................................... 8
7.2 Functional Block Diagram ......................................... 8
7.3 Feature Description................................................... 8
7.4 Device Functional Modes........................................ 10
8
Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Application .................................................. 11
9 Power Supply Recommendations...................... 15
10 Layout................................................................... 15
10.1 Layout Guidelines ................................................. 15
10.2 Layout Examples................................................... 15
10.3 Thermal Considerations ........................................ 16
11 Device and Documentation Support ................. 17
11.1
11.2
11.3
11.4
11.5
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
17
17
17
17
17
12 Mechanical, Packaging, and Orderable
Information ........................................................... 17
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision B (June 2013) to Revision C
Page
•
Deleted Ordering Information table ....................................................................................................................................... 1
•
Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section ............................... 1
Changes from Revision A (October 2011) to Revision B
Page
•
Removed (SWIFT™) from the data sheet title ....................................................................................................................... 1
•
Added "and 10-pin DRC" to the DESCRIPTION .................................................................................................................... 1
•
Added the DRC-10 Pin package pin out ................................................................................................................................ 3
•
Changed the VBST(vs SW) MAX value From: 5.7V to 6V in the ROC table......................................................................... 4
•
Added High-side switch resistance (DRC) ............................................................................................................................. 5
•
Added a conditions statement "VIN = 12 V, TA = 25°C" to the TYPICAL CHARACTERISTICS .......................................... 6
•
Changed Figure 11 title From: 1.05-V, 50-mA to 2-A LOAD TRANSIENT RESPONSE To: 1.05-V, 0-A to 2-A LOAD
TRANSIENT RESPONSE .................................................................................................................................................... 13
•
Added Figure 18 ................................................................................................................................................................... 16
Changes from Original (May 2010) to Revision A
Page
•
Corrected the pin numbers for Pins 5 through 8 .................................................................................................................... 3
•
Added REN - EN pin resistance to GND to the LOGIC THRESHOLD section of the ELECTRICAL
CHARACTERISTICS table ..................................................................................................................................................... 5
2
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SLVSAU2C – MAY 2011 – REVISED DECEMBER 2015
5 Pin Configuration and Functions
DDA Package
8-Pin HSOP
Top View
1
DRC Package
10-Pin VSON
Top View
VIN
EN
10 VIN
EN 1
8
VFB 2
2
VBST
VFB
VREG5 3
7
TPS54227
(HSOP8)
3
VREG5
4
SS
Exposed
Thermal
Die PAD
on
Underside
PGND
SS 4
PowerPADTM
SW
6
GND
5
GND 5
9 VIN
8 VBST
7 SW
6 SW
Pin Functions
PIN
NAME
DDA
DRC
EN
1
1
Exposed
Thermal
Pad
—
GND
5
SS
SW
I/O
I
G
—
DESCRIPTION
Enable input control. EN is active high and must be pulled up to enable the device.
Thermal pad of the package. Must be soldered to achieve appropriate dissipation. Must
be connected to GND.
Thermal pad of the package. PGND power ground return of internal low-side FET. Must
be soldered to achieve appropriate dissipation.
5
G
Ground pin. Power ground return for switching circuit. Connect sensitive SS and VFB
returns to GND at a single point.
4
4
O
Soft-start control. An external capacitor should be connected to GND.
6
6, 7
O
Switch node connection between high-side NFET and low-side NFET.
VBST
7
8
I
Supply input for the high-side FET gate drive circuit. Connect 0.1-µF capacitor between
VBST and SW pins. An internal diode is connected between VREG5 and VBST.
VFB
2
2
I
Converter feedback input. Connect to output voltage with feedback resistor divider.
VIN
8
9, 10
P
Input voltage supply pin.
VREG5
3
3
O
5.5-V power supply output. A capacitor (typical 1 µF) should be connected to GND.
VREG5 is not active when EN is low.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
Input voltage
MIN
MAX
UNIT
VIN, EN
–0.3
20
V
VBST
–0.3
26
V
VBST (10-ns transient)
–0.3
28
V
VBST (vs SW)
–0.3
6.5
V
VFB, SS
–0.3
6.5
V
SW
–2
20
V
SW (10-ns transient)
–3
22
V
VREG5
–0.3
6.5
V
GND
–0.3
0.3
V
Voltage from GND to thermal pad, Vdiff
–0.2
0.2
V
Operating junction temperature, TJ
–40
150
°C
Storage temperature, Tstg
–55
150
°C
Output voltage
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001
(1)
UNIT
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
V
±500
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
VIN
VI
MIN
MAX
4.5
18
VBST
–0.1
24
VBST (10 ns transient)
-0.1
27
VBST(vs SW)
–0.1
6
SS
–0.1
5.7
EN
–0.1
18
VFB
–0.1
5.5
SW
–1.8
18
Supply input voltage range
Input voltage range
SW (10 ns transient)
UNIT
V
V
–3
21
GND
–0.1
0.1
–0.1
5.7
V
VO
Output voltage range
VREG5
IO
Output Current range
IVREG5
0
10
mA
TA
Operating free-air temperature
–40
85
°C
TJ
Operating junction temperature
–40
150
°C
4
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6.4 Thermal Information
TPS54227
THERMAL METRIC (1)
DDA (HSOP)
DRC (VSON)
8 PINS
10 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance
45.3
43.9
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
54.8
55.4
°C/W
RθJB
Junction-to-board thermal resistance
16.2
18.9
°C/W
ψJT
Junction-to-top characterization parameter
6.6
0.7
°C/W
ψJB
Junction-to-board characterization parameter
16
19.1
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
8.5
5.3
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
6.5 Electrical Characteristics
over operating free-air temperature range, VIN = 12 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
800
1200
μA
5
10
μA
SUPPLY CURRENT
IVIN
Operating - non-switching supply current
VIN current, TA = 25°C, EN = 5 V, VFB = 0.8 V
IVINSDN
Shutdown supply current
VIN current, TA = 25°C, EN = 0 V
LOGIC THRESHOLD
VENH
EN high-level input voltage
EN
VENL
EN low-level input voltage
EN
1.6
V
REN
EN pin resistance to GND
VEN = 12 V
220
440
749
0.6
V
880
kΩ
765
781
mV
0
±0.1
μA
5.5
5.7
V
25
mV
100
mV
VFB VOLTAGE AND DISCHARGE RESISTANCE
VFBTH
VFB threshold voltage
TA = 25°C, VO = 1.05 V, continuous mode
IVFB
VFB input current
VFB = 0.8 V, TA = 25°C
VVREG5
VREG5 output voltage
TA = 25°C, 6 V < VIN < 18 V, 0 < IVREG5 < 5 mA
VLN5
Line regulation
6 V < VIN < 18 V, IVREG5 = 5 mA
VLD5
Load regulation
0 mA < IVREG5 < 5 mA
IVREG5
Output current
VIN = 6 V, VREG5 = 4 V, TA = 25°C
VREG5 OUTPUT
5.2
60
mA
MOSFET
RDS(on)h
RDS(on)l
High-side switch resistance (DDA)
High-side switch resistance (DRC)
Low-side switch resistance
155
25°C, VBST - SW = 5.5 V
mΩ
165
25°C
108
mΩ
CURRENT LIMIT
Iocl
Current limit
L out = 2.2 μH (1)
2.5
3.3
4.7
A
THERMAL SHUTDOWN
TSDN
Thermal shutdown threshold
Shutdown temperature
Hysteresis
(1)
165
(1)
°C
35
ON-TIME TIMER CONTROL
tON
ON-time
VIN = 12 V, VO = 1.05 V
150
tOFF(MIN)
Minimum OFF-time
TA = 25°C, VFB = 0.7 V
260
310
ns
ISSC
SS charge current
VSS = 1V
1.4
2
2.6
ISSD
SS discharge current
VSS = 0.5 V
0.1
0.2
Wake up VREG5 voltage
3.45
3.75
4.05
Hysteresis VREG5 voltage
0.13
0.32
0.48
ns
SOFT-START
μA
mA
UVLO
UVLO
(1)
UVLO threshold
V
Not production tested.
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6.6 Typical Characteristics
VIN = 12 V, TA = 25°C (unless otherwise noted)
14
1200
12
Ivccsdn - Shutdown Current - mA
ICC - Supply Current - mA
1000
800
600
400
200
10
VIN = 12 V
8
6
4
2
0
-50
0
50
100
TJ - Junction Temperature - °C
0
-50
150
Figure 1. VIN Current vs Junction Temperature
0
50
100
TJ - Junction Temperature - °C
150
Figure 2. VIN Shutdown Current vs
Junction Temperature
100
100
VO = 3.3 V
90
90
70
80
Efficiency - %
EN - Input Current - mA
80
60
50
VIN = 18 V
40
VO = 2.5 V
VO = 1.8 V
70
60
30
20
50
10
0
40
0
5
10
VI - Input Voltage - V
15
0
20
1.5
2
900
850
850
VO = 1.8 V
800
VO = 3.3 V
VO = 2.5 V
fsw - Switching Frequency - kHz
fsw - Switching Frequency - kHz
1
IO - Output Current - A
Figure 4. Efficiency vs Output Current
Figure 3. EN Current vs EN Voltage
900
750
700
650
600
VO = 5 V
VO = 1.5 V
VO = 1.2 V
550
VO = 1.05 V
500
450
800
VO = 1.8 V
VO = 3.3 V
750
700
650
VO = 1.05 V
600
550
500
450
400
400
0
5
10
VI - Input Voltage - V
15
20
0
Figure 5. Switching Frequency vs Input Voltage
6
0.5
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0.5
1
IO - Output Current - A
1.5
2
Figure 6. Switching Frequency vs
Output Current
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Typical Characteristics (continued)
VIN = 12 V, TA = 25°C (unless otherwise noted)
0.780
VFBTH - Vfb Voltage - V
0.775
0.770
0.765
0.760
0.755
0.750
-50
0
50
100
o
TJ - Junction Temperature - C
150
Figure 7. Vfb Voltage vs Junction Temperature
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7 Detailed Description
7.1 Overview
The TPS54227 is a 2-A synchronous step-down (buck) converter with two integrated N-channel MOSFETs. It
operates using D-CAP2 mode control. The fast transient response of D-CAP2 control reduces the output
capacitance required to meet a specific level of performance. Proprietary internal circuitry allows the use of low
ESR output capacitors including ceramic and special polymer types.
7.2 Functional Block Diagram
EN
1
EN
VIN
Logic
VIN
8
VREG5
Control Logic
Ref
+
SS
+ PWM
7
1 shot
VFB
SW
VO
6
-
2
VBST
XCON
ON
VREG5
VREG5
Ceramic
Capacitor
3
SGND
SS
SS
4
5
Softstart
GND
PGND
SGND
+
OCP
-
SW
PGND
VIN
UVLO
VREG5
UVLO
REF
TSD
Protection
Logic
Ref
7.3 Feature Description
7.3.1 PWM Operation
The main control loop of the TPS54227 is an adaptive ON-time pulse width modulation (PWM) controller that
supports a proprietary D-CAP2 mode control. D-CAP2 mode control combines constant ON-time control with an
internal compensation circuit for pseudo-fixed frequency and low external component count configuration with
both low ESR and ceramic output capacitors. It is stable even with virtually no ripple at the output.
At the beginning of each cycle, the high-side MOSFET is turned on. This MOSFET is turned off after internal one
shot timer expires. This one shot is set by the converter input voltage, VIN, and the output voltage, VO, to
maintain a pseudo-fixed frequency over the input voltage range, hence it is called adaptive ON-time control. The
one-shot timer is reset and the high-side MOSFET is turned on again when the feedback voltage falls below the
reference voltage. An internal ramp is added to reference voltage to simulate output ripple, eliminating the need
for ESR induced output ripple from D-CAP2 mode control.
8
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Feature Description (continued)
7.3.2 PWM Frequency and Adaptive ON-Time Control
TPS54227 uses an adaptive ON-time control scheme and does not have a dedicated on board oscillator. The
TPS54227 runs with a pseudo-constant frequency of 700 kHz by using the input voltage and output voltage to
set the ON-time one-shot timer. The ON-time is inversely proportional to the input voltage and proportional to the
output voltage, therefore, when the duty ratio is VOUT / VIN, the frequency is constant.
7.3.3 Soft-Start and Prebiasd Soft-Start
The soft-start function is adjustable. When the EN pin becomes high, 2-μA current begins charging the capacitor
which is connected from the SS pin to GND. Smooth control of the output voltage is maintained during start-up.
The equation for the slow start time is shown in Equation 1. VFB voltage is 0.765 V and SS pin source current is
2 μA.
t
SS
(ms) =
C6(nF) x V
x 1.1 C6(nF) x 0.765 x 1.1
REF
=
I (mA)
2
SS
(1)
The TPS54227 contains a unique circuit to prevent current from being pulled from the output during start-up if the
output is prebiased. When the soft-start commands a voltage higher than the prebias level (internal soft-start
becomes greater than feedback voltage VFB), the controller slowly activates synchronous rectification by starting
the first low-side FET gate driver pulses with a narrow ON-time. It then increments that ON-time on a cycle-bycycle basis until it coincides with the time dictated by (1-D), where D is the duty cycle of the converter. This
scheme prevents the initial sinking of the prebias output, and ensure that the out voltage (VO) starts and ramps
up smoothly into regulation and the control loop is given time to transition from prebiased start-up to normal
mode operation.
7.3.4 Current Protection
The output overcurrent protection (OCP) is implemented using a cycle-by-cycle valley detect control circuit. The
switch current is monitored by measuring the low-side FET switch voltage between the SW pin and GND. This
voltage is proportional to the switch current. To improve accuracy, the voltage sensing is temperature
compensated.
During the ON-time of the high-side FET switch, the switch current increases at a linear rate determined by VIN,
VOUT, the ON-time and the output inductor value. During the ON-time of the low-side FET switch, this current
decreases linearly. The average value of the switch current is the load current IOUT. The TPS54227 constantly
monitors the low-side FET switch voltage, which is proportional to the switch current, during the low-side
ON-time. If the measured voltage is above the voltage proportional to the current limit, an internal counter is
incremented per each SW cycle and the converter maintains the low-side switch on until the measured voltage is
below the voltage corresponding to the current limit at which time the switching cycle is terminated and a new
switching cycle begins. In subsequent switching cycles, the ON-time is set to a fixed value and the current is
monitored in the same manner. If the overcurrent condition exists for 7 consecutive switching cycles, the internal
OCL threshold is set to a lower level, reducing the available output current. When a switching cycle occurs where
the switch current is not above the lower OCL threshold, the counter is reset and the OCL limit is returned to the
higher value.
There are some important considerations for this type of overcurrent protection. The load current one half of the
peak-to-peak inductor current higher than the overcurrent threshold. Also when the current is being limited, the
output voltage tends to fall as the demanded load current may be higher than the current available from the
converter. This may cause the output voltage to fall. When the overcurrent condition is removed, the output
voltage returns to the regulated value. This protection is non-latching.
7.3.5 UVLO Protection
Undervoltage lockout protection (UVLO) monitors the voltage of the VREG5 pin. When the VREG5 voltage is lower
than UVLO threshold voltage, the TPS54227 is shut off. This is protection is non-latching.
7.3.6 Thermal Shutdown
TPS54227 monitors the temperature of itself. If the temperature exceeds the threshold value (typically 165°C),
the device is shut off. This is non-latch protection.
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7.4 Device Functional Modes
7.4.1 Normal Operation
When the input voltage is above the UVLO threshold and the EN voltage is above the enable threshold, the
TPS54227 operates in normal switching mode. Normal continuous conduction mode (CCM) occurs when the
minimum switch current is above 0 A. In CM the TPS54227 operates at a quasi-fixed frequency of 650 kHz.
7.4.2 Forced CCM Operation
When the TPS54227 is in normal CCM operating mode and the switch current falls below 0 A, the device begins
operating in forced CCM.
10
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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 TPS54227 is used as a step converter that converts a voltage of 4.5 to 18 V to a lower voltage.
WEBENCH™ software is available to aid in the design and analysis of circuits.
8.2 Typical Application
U1
TPS54227DDA
Figure 8. Typical Application
8.2.1 Design Requirements
Table 1 lists the design requirements for this example.
Table 1. Design Requirements
SPECIFICATIONS
TEST CONDITIONS
Input voltage
MIN
TYP
MAX
4.5
12
18
Output voltage
Operating frequency
VIN = 12 V, Io = 1 A
Output current range
0
UNIT
V
1.05
V
700
kHz
12
A
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8.2.2 Detailed Design Procedure
To
•
•
•
•
•
begin the design process, you must know a few application parameters:
Input voltage range
Output voltage
Output current
Output voltage ripple
Input voltage ripple
8.2.2.1 Output Voltage Resistors Selection
The output voltage is set with a resistor divider from the output node to the VFB pin. TI recommends to use 1%
tolerance or better divider resistors. Start by using Equation 2 to calculate VOUT.
To improve efficiency at very light loads consider using larger value resistors, too high of resistance is more
susceptible to noise and voltage errors from the VFB input current is more noticeable.
V
= 0.765 x
OUT
æ
ö
çç1 + R1÷÷
÷
çè
R2 ø
(2)
8.2.2.2 Output Filter Selection
The output filter used with the TPS54227 is an LC circuit. This LC filter has double pole at:
F =
P
2p L
1
OUT
x COUT
(3)
At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54227. The low frequency phase is 180 degrees. At the output filter pole frequency, the gain rolls
off at a –40 dB per decade rate and the phase drops rapidly. D-CAP2 introduces a high frequency zero that
reduces the gain roll off to –20 dB per decade and increases the phase to 90 degrees one decade above the
zero frequency. The inductor and capacitor selected for the output filter must be selected so that the double pole
of Equation 3 is located below the high frequency zero but close enough that the phase boost provided be the
high frequency zero provides adequate phase margin for a stable circuit. To meet this requirement use the
values recommended in Table 2.
Table 2. Recommended Component Values
Output Voltage (V)
R1 (kΩ)
R2 (kΩ)
(1)
C4 (pF) (1)
L1 (µH)
C8 + C9 (µF)
1
6.81
22.1
1.5 - 2.2
22 - 68
1.05
8.25
22.1
1.5 - 2.2
22 - 68
1.2
12.7
22.1
2.2
22 - 68
1.5
21.5
22.1
2.2
22 - 68
1.8
30.1
22.1
5 - 22
3.3
22 - 68
2.5
49.9
22.1
5 - 22
3.3
22 - 68
3.3
73.2
22.1
5 - 22
3.3
22 - 68
5
124
22.1
5 - 22
4.7
22 - 68
6.5
165
22.1
5 - 22
4.7
22 - 68
Optional
Because the DC gain is dependent on the output voltage, the required inductor value increases as the output
voltage increases. For higher output voltages at or above 1.8 V, additional phase boost can be achieved by
adding a feed forward capacitor (C4) in parallel with R1
The inductor peak-to-peak ripple current, peak current and RMS current are calculated using Equation 4,
Equation 5 and Equation 6. The inductor saturation current rating must be greater than the calculated peak
current and the RMS or heating current rating must be greater than the calculated RMS current. Use 700 kHz for
fSW.
Use 700 kHz for fSW. Make sure the chosen inductor is rated for the peak current of Equation 5 and the RMS
current of Equation 6.
12
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- VOUT
V
V
OUT x IN(max)
I
=
IPP
V
L x f
IN(max)
O
SW
I
=I +
Ipeak
O
=
I
Lo(RMS)
(4)
I
lpp
2
I
2
O
(5)
+
1
2
I
12 IPP
(6)
For this design example, the calculated peak current is 2.311 A and the calculated RMS current is 2.008 A. The
inductor used is a TDK CLF7045T-2R2M with a peak current rating of 5.5 A and an RMS current rating of 4.3 A.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54227 is intended for use
with ceramic or other low ESR capacitors. Recommended values range from 22 µF to 68 µF. Use Equation 7 to
determine the required RMS current rating for the output capacitor.
I
Co(RMS)
=
VOUT x (VIN - VOUT )
12 x VIN x LO x fSW
(7)
For this design two TDK C3216X5R0J226M 22-µF output capacitors are used. The typical ESR is 2 mΩ each.
The calculated RMS current is 0.18 A and each output capacitor is rated for 4A.
8.2.2.3 Input Capacitor Selection
The TPS54227 requires an input decoupling capacitor and a bulk capacitor is needed depending on the
application. A ceramic capacitor over 10 μF is recommended for the decoupling capacitor. An additional 0.1-µF
capacitor (C3) from pin 8 to ground is optional to provide additional high frequency filtering. The capacitor voltage
rating needs to be greater than the maximum input voltage.
8.2.2.4 Bootstrap Capacitor Selection
A 0.1-µF ceramic capacitor must be connected between the VBST to SW pin for proper operation. TI
recommends to use a ceramic capacitor.
8.2.2.5 VREG5 Capacitor Selection
A 1-µF ceramic capacitor must be connected between the VREG5 to GND pin for proper operation. TI
recommends to use a ceramic capacitor.
8.2.3 Application Curves
1.1
1.08
1.07
VO - Output Voltage - V
VO - Output Voltage - V
VI = 1.8 V
VI = 1.2 V
1.075
1.05
VI = 5 V
IO = 0 A
1.06
IO = 1 A
1.05
1.025
1.04
1
0
0.5
1
IO - Output Current - A
1.5
2
Figure 9. 1.05-V Output Voltage vs Output Current
0
5
10
VI - Input Voltage - V
15
20
Figure 10. 1.05-V Output Voltage vs Input Voltage
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EN (10 V/div)
Vout (50 mV/div)
VREG5 (5 V/div)
Iout (1 A/div)
Vout (0.5 V/div)
100 ms/div
t - Time - 1 ms
Figure 11. 1.05-V, 0-A to 2-A Load Transient Response
Figure 12. Start-Up Waveform
VO = 1.05 V
VO = 1.05 V
VIN (50 mV/div)
VO (10 mV/div)
SW (5 V/div)
SW (5 V/div)
t - Time - 400 ns
t - Time - 400 ns
Figure 14. Voltage Ripple at Output (IO = 2 A)
100
100
90
90
80
80
70
70
Efficiency - %
Efficiency - %
Figure 13. Voltage Ripple at Output (IO = 2 A)
60
50
40
30
50
40
30
20
20
VIN = 5 V
VIN = 12 V
10
0
0.5
1
Output Current - A
1.5
VIN = 5 V
VIN = 12 V
10
0
2
0
0.01
D001
Figure 15. TPS54227EVM-686 Efficiency
14
60
0.1
1
Output Current - A
10
D001
Figure 16. TPS54227EVM-686 Light Load Efficiency
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9 Power Supply Recommendations
The TPS54227 is designed to operate from input supply voltage in the range of 4.5 V to 18 V. Buck converters
require the input voltage to be higher than the output voltage.
10 Layout
10.1 Layout Guidelines
1. Keep the input switching current loop as small as possible.
2. Keep the SW node as physically small and short as possible to minimize parasitic capacitance and
inductance and to minimize radiated emissions. Kelvin connections should be brought from the output to the
feedback pin of the device.
3. Keep analog and non-switching components away from switching components.
4. Make a single point connection from the signal ground to power ground.
5. Do not allow switching current to flow under the device.
6. Keep the pattern lines for VIN and PGND broad.
7. Exposed pad of device must be connected to PGND with solder.
8. VREG5 capacitor should be placed near the device, and connected PGND.
9. Output capacitor should be connected to a broad pattern of the PGND.
10. Voltage feedback loop should be as short as possible, and preferably with ground shield.
11. Lower resistor of the voltage divider which is connected to the VFB pin should be tied to SGND.
12. Providing sufficient via is preferable for VIN, SW and PGND connection.
13. PCB pattern for VIN, SW, and PGND should be as broad as possible.
14. VIN Capacitor should be placed as near as possible to the device.
10.2 Layout Examples
VIN
FEEDBACK
RESISTORS
TO ENABLE
CONTROL
BIAS
CAP
VIN
INPUT
BYPASS
CAPACITOR
VIN
HIGH FREQENCY
BYPASS
CAPACITOR
EN
VIN
VFB
VBST
VREG5
SW
SS
GND
BOOST
CAPACITOR
OUTPUT
INDUCTOR
SLOW
START
CAP
Connection to
POWER GROUND
on internal or
bottom layer
ANALOG
GROUND
TRACE
EXPOSED
THERMAL PAD
AREA
VOUT
OUTPUT
FILTER
CAPACITOR
POWER GROUND
VIA to Ground Plane
Figure 17. PCB Layout for the DDA Package
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Layout Examples (continued)
VIN
FEEDBACK
RESISTORS
TO ENABLE
CONTROL
EN
VIN
HIGH FREQENCY
BYPASS
VIN CAPACITOR
VFB
VIN
VREG5
BIAS
CAP
SLOW
START
CAP
ANALOG
GROUND
TRACE
VIN
INPUT
BYPASS
CAPACITOR
VBST
SS
SW
GND
SW
BOOST
CAPACITOR
OUTPUT
INDUCTOR
OUTPUT
FILTER
CAPACITOR
EXPOSED
THERMAL PAD
AREA
Connection to
POWER GROUND
on internal or
bottom layer
VOUT
POWER GROUND
VIA to Ground Plane
Figure 18. PCB Layout for the DRC Package
10.3 Thermal Considerations
This 8-pin HSOP package incorporates an exposed thermal pad that is designed to be directly to an external
heartsick. The thermal pad must be soldered directly to the printed-circuit-board (PCB). After soldering, the PCB
can be used as a heartsick. In addition, through the use of thermal vias, the thermal pad can be attached directly
to the appropriate copper plane shown in the electrical schematic for the device, or alternatively, can be attached
to a special heartsick structure designed into the PCB. This design optimizes the heat transfer from the
integrated circuit (IC).
For additional information on the exposed thermal pad and how to use the advantage of its heat dissipating
abilities, refer to PowerPAD™ Thermally Enhanced Package (SLMA002) and PowerPAD™ Made Easy
(SLMA004).
The exposed thermal pad dimensions for this package are shown in Figure 19.
Figure 19. Thermal Pad Dimensions (Top View)
16
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
• PowerPAD™ Thermally Enhanced Package, SLMA002
• PowerPAD™ Made Easy, SLMA004
11.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.3 Trademarks
D-CAP2, WEBENCH, PowerPAD, E2E are trademarks of Texas Instruments.
Blu-ray Disc is a trademark of Blu-ray Disc Association.
All other trademarks are the property of their respective owners.
11.4 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.
11.5 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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17
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)
TPS54227DDA
ACTIVE SO PowerPAD
DDA
8
75
RoHS & Green
NIPDAU | SN
Level-2-260C-1 YEAR
-40 to 85
54227
TPS54227DDAR
ACTIVE SO PowerPAD
DDA
8
2500
RoHS & Green
NIPDAU | SN
Level-2-260C-1 YEAR
-40 to 85
54227
TPS54227DRCR
ACTIVE
VSON
DRC
10
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
54227
TPS54227DRCT
ACTIVE
VSON
DRC
10
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
54227
(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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