TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
4.5V to 23V Input, 2-A Synchronous Step-Down SWIFT™ Converter
Check for Samples: TPS54239
FEATURES
DESCRIPTION
•
The TPS54239 is an adaptive on-time D-CAP2™
mode synchronous buck converter. The TPS54239
enables system designers to complete the suite of
various end-equipment power bus regulators with a
cost effective, low component count, low standby
current solution. The main control loop for the
TPS54239 uses the D-CAP2™ mode control that
provides a fast transient response with no external
compensation components. The TPS54239 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 23-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
TPS54239 is available in the 8-pin DDA package,
and designed to operate from –40°C to 85°C.
1
23
•
•
•
•
•
•
•
•
•
•
D-CAP2™ Mode Enables Fast Transient
Response
Low Output Ripple and Allows Ceramic Output
Capacitor
Wide VIN Input Voltage Range: 4.5 V to 23 V
Output Voltage Range: 0.76 V to 7.0 V
Highly Efficient Integrated FETs Optimized
for Lower Duty Cycle Applications
– 140 mΩ (High Side) and 70 mΩ (Low Side)
High Efficiency, less than 10 μA at shutdown
High Initial Bandgap Reference Accuracy
Adjustable Soft Start
Pre-Biased Soft Start
600-kHz Switching Frequency (fSW)
Cycle By Cycle Over Current Limit
APPLICATIONS
•
Wide Range of Applications for Low Voltage
System
– Digital TV Power Supply
– High Definition Blu-ray Disc™ Players
– Networking Home Terminal
– Digital Set Top Box (STB)
VIN
Vout (50 mV/div)
TPS54239DDA
1
2
VOUT
3
4
VBST
SS
VIN
EN
SW
VREG5
8
7
EN
Iout (1 A/div)
6
5
GND
VFB
VOUT
PwPd
9
100 us/div
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
D-CAP2 is a trademark of Texas Instruments.
Blu-ray Disc is a trademark of Blu-ray Disc Association.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2013, Texas Instruments Incorporated
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
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.
ORDERING INFORMATION (1)
PACKAGE (2)
TA
–40°C to 85°C
(1)
(2)
(3)
(3)
ORDERABLE PART NUMBER
TPS54239DDA
DDA
TRANSPORT
MEDIA
PIN
Tube
8
TPS54239DDAR
Tape and Reel
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
Package drawings, thermal data, and symbolization are available at www.ti.com/packaging.
All package options have Cu NIPDAU lead/ball finish.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)
(1)
VALUE
Input voltage range
Output voltage range
MAX
VIN, EN
–0.3
25
VBST
–0.3
31
VBST (10 ns transient)
–0.3
33
VBST (vs SW)
–0.3
6.5
VFB, SS
–0.3
6.5
SW
–2
25
SW (10 ns transient)
–3
27
VREG5
–0.3
6.5
GND
–0.3
0.3
–0.2
0.2
V
2
kV
500
V
Voltage from GND to thermal pad, Vdiff
Electrostatic discharge
Human Body Model (HBM)
Charged Device Model (CDM)
Operating junction temperature, TJ
–40
150
Storage temperature, Tstg
–55
150
(1)
UNIT
MIN
V
V
°C
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
THERMAL INFORMATION
THERMAL METRIC (1)
TPS54239
DDA (8 PINS)
θJA
Junction-to-ambient thermal resistance
46.2
θJCtop
Junction-to-case (top) thermal resistance
53.9
θJB
Junction-to-board thermal resistance
29.7
ψJT
Junction-to-top characterization parameter
10.0
ψJB
Junction-to-board characterization parameter
29.6
θJCbot
Junction-to-case (bottom) thermal resistance
6.6
(1)
2
UNITS
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
RECOMMENDED OPERATING CONDITIONS
over operating free-air temperature range, (unless otherwise noted)
VIN
Supply input voltage range
VI
Input voltage range
MIN
MAX
4.5
23
VBST
–0.1
29
VBST (10 ns transient)
–0.1
32
VBST(vs SW)
–0.1
5.7
SS
–0.1
5.7
EN
–0.1
23
VFB
–0.1
5.5
SW
–1.8
23
SW (10 ns transient)
UNIT
V
V
–3
26
GND
–0.1
0.1
–0.1
5.7
V
0
10
mA
VO
Output voltage range
VREG5
IO
Output Current range
IVREG5
TA
Operating free-air temperature
–40
85
°C
TJ
Operating junction temperature
–40
150
°C
ELECTRICAL CHARACTERISTICS
over operating free-air temperature range, VIN = 12 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CURRENT
IVIN
Operating - non-switching supply current VIN current, TA = 25°C, EN = 5V, VFB = 0.8V
850
1200
μA
IVINSDN
Shutdown supply current
3.0
10
μA
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
REN
EN pin resistance to GND
VEN = 12 V
200
749
V
0.6
V
400
800
kΩ
765
781
mV
0
±0.1
μA
5.5
5.7
V
VFB VOLTAGE AND DISCHARGE RESISTANCE
VFBTH
VFB threshold voltage
TA = 25°C, VO = 1.05 V, continuous mode
operation
IVFB
VFB input current
VFB = 0.8 V, TA = 25°C
VREG5 OUTPUT
VVREG5
VREG5 output voltage
TA = 25°C, 6.0 V < VIN < 23 V,
0 < IVREG5 < 5 mA
5.2
IVREG5
Output current
VIN = 6 V, VREG5 = 4.0 V, TA = 25°C
20
RDS(on)h
High side switch resistance
25°C, VBST - SW = 5.5 V (1)
RDS(on)l
Low side switch resistance
25°C (1)
mA
MOSFET
140
mΩ
70
mΩ
CURRENT LIMIT
Iocl
Current limit
L out = 2.2 μH (1)
2.5
3.1
4.6
A
THERMAL SHUTDOWN
TSDN
Thermal shutdown threshold
Shutdown temperature
Hysteresis
(1)
(1)
165
°C
40
ON-TIME TIMER CONTROL
tON
On time
tOFF(MIN)
(1)
Minimum off time
VIN = 12 V, VO = 1.05 V
TA = 25°C, VFB = 0.7 V
(1)
160
260
ns
310
ns
Not production tested.
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
3
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
over operating free-air temperature range, VIN = 12 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
7.8
UNIT
SOFT START
ISSC
SS charge current
VSS = 1.0 V
4.2
6.0
ISSD
SS discharge current
VSS = 0.5 V
0.8
1.5
μA
mA
HICCUP AND OVERVOLTAGE PROTECTION
VOVP
Output OVP threshold
OVP Detect (L>H)
VUVP
Output Hiccup threshold
Hiccup detect (H>L)
TUVPDEL
Output Hiccup delay
to Hiccup state
TUVPEN
Output Hiccup Enable delay
Relative to soft-start time
125%
65%
6
µs
x1.7
UVLO
UVLO
UVLO threshold
Wake up VREG5 voltage
3.45
3.75
4.05
Hysteresis VREG5 voltage
0.17
0.33
0.47
V
DEVICE INFORMATION
DDA PACKAGE
(TOP VIEW)
1
VBST
2
VIN
SS
8
EN
7
VREG5
6
POWER PAD
TPS54239
DDA
3
SW
4
GND
HSOP8
VFB
5
PIN FUNCTIONS
PIN
DESCRIPTION
NAME
NO.
VBST
1
Supply input for the high-side FET gate drive circuit. Connect 0.1µF capacitor between VBST and SW pins.
An internal diode is connected between VREG5 and VBST.
VIN
2
Input voltage supply pin.
SW
3
Switch node connection between high-side NFET and low-side NFET.
GND
4
Ground pin. Power ground return for switching circuit. Connect sensitive SS and VFB returns to GND at a
single point.
VFB
5
Converter feedback input. Connect to output voltage with feedback resistor divider.
4
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
PIN FUNCTIONS (continued)
PIN
DESCRIPTION
NAME
NO.
VREG5
6
5.5 V power supply output. A capacitor (typical 0.47 µF) should be connected to GND. VREG5 is not active
when EN is low.
EN
7
Enable input control. EN is active high and must be pulled up to enable the device.
SS
8
Soft-start control. An external capacitor should be connected to GND.
Exposed
Thermal Pad
Thermal pad of the package. Must be soldered to achieve appropriate dissipation. Must be connected to
GND.
Back side
FUNCTIONAL BLOCK DIAGRAM
SS
8
Softstart
SS
1
VBST
VIN
SGND
VIN
EN
EN
7
2
Logic
VREG5
VREG5
Control Logic
6
1 Shot
OV
SW
3
+25%
VO
XCON
VREG5
PGND
Ref
SS
Ceramic
Capacitor
PWM
4
GND
5
VFB
SW
SGND
OCP
PGND
VIN
OV
VREG5
UVLO
UVLO
REF
TSD
Protection
Logic
Ref
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
5
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
OVERVIEW
The TPS54239 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.
DETAILED DESCRIPTION
PWM Operation
The main control loop of the TPS54239 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.
PWM Frequency and Adaptive On-Time Control
TPS54239 uses an adaptive on-time control scheme and does not have a dedicated on board oscillator. The
TPS54239 runs with a pseudo-constant frequency of 600 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.
Soft Start and Pre-Biased Soft Start
The soft start function is adjustable. When the EN pin becomes high, 6 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
6 μA.
t
SS
(ms) =
CSS (nF) x VREF ´1.1
I (mA)
SS
=
CSS (nF) x 0.765 ´1.1
6
(1)
The TPS54239 contains a unique circuit to prevent current from being pulled from the output during startup if the
output is pre-biased. When the soft-start commands a voltage higher than the pre-bias 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 pre-bias 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 pre-biased start-up to normal
mode operation.
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 TPS54239 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
6
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
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 over current 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 over-current protection. The load current one half of the
peak-to-peak inductor current higher than the over-current 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 VFB voltage becomes lower than 65% of the
target voltage, the UVP comparator detects it. After 6µs detecting the UVP voltage, device will shut down and restart after 7 times SS period for Hiccup.
When the over current condition is removed, the output voltage returns to the regulated value. This protection is
non-latching.
Over Voltage Protection
TPS54239 detects over voltage conditions by monitoring the feedback voltage (VFB). This function is enabled
after approximately 1.7 x times the soft start time.
When the feedback voltage becomes higher than 125% of the target voltage, the OVP comparator output goes
high and both the high-side MOSFET driver and the low-side MOSFET driver turn off. This function is non-latch
operation.
UVLO Protection
Undervoltage lock out protection (UVLO) monitors the voltage of the VREG5 pin. When the VREG5 voltage is lower
than UVLO threshold voltage, the TPS54239 is shut off. This protection is non-latching.
Thermal Shutdown
TPS54239 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.
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
7
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
TYPICAL CHARACTERISTICS
VIN = 12 V, TA = 25°C (unless otherwise noted).
10
Ivccsdn ± Shutdown Current ( A)
ICC ± Supply Current ( A)
1200
1000
800
600
400
200
0
8
6
4
2
0
±50
0
50
100
±50
150
TJ ± Junction Temperature (ƒC)
0
50
100
150
TJ ± Junction Temperature (ƒC)
C001
Figure 1. VIN CURRENT vs JUNCTION TEMPERATURE
C002
Figure 2. VIN SHUTDOWN CURRENT vs
JUNCTION TEMPERATURE
1.100
80
VOUT ± Output Voltage (V)
EN Input Current ( A)
VIN = 23 V
60
40
20
VIN = 23 V
1.075
VIN = 12 V
1.050
VIN = 5 V
1.025
1.000
0
0
5
10
15
20
EN Input Voltage (V)
25
0.0
Figure 3. EN CURRENT vs EN VOLTAGE
0.5
1.0
1.5
2.0
IOUT ± Output Current (A)
C003
C004
Figure 4. 1.05-V OUTPUT VOLTAGE vs OUTPUT CURRENT
VOUT ± Output Voltage (V)
1.07
IOUT = 0 A
Vout (50 mV/div)
1.06
1.05
Iout (1 A/div)
IOUT = 1 A
1.04
100 us/div
1.03
0
5
10
15
VIN ± Input Voltage (V)
20
25
C005
Figure 5. 1.05-V OUTPUT VOLTAGE vs INPUT VOLTAGE
8
Figure 6. 1.05-V, LOAD TRANSIENT RESPONSE
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
TYPICAL CHARACTERISTICS
VIN = 12 V, TA = 25°C (unless otherwise noted).
100
90
Efficiency (%)
EN (10 V/div)
VREG5 (5 V/div)
Vout (0.5 V/div)
80
VO = 3.3 V
VO = 5 V
VO = 1.8 V
70
60
50
400 us/div
40
0.0
0.5
1.0
1.5
IOUT ± Output Current (A)
Figure 7. START-UP WAVE FORM
C006
Figure 8. EFFICIENCY vs OUTPUT CURRENT
900
800
850
fSW ± Switching Frequency (kHz)
fSW ± Switching Frequency (kHz)
2.0
800
750
VO = 5 V
700
VO = 3.3 V
VO = 1.8 V
650
600
550
VO = 1.2 V
500
450
VO = 1.05 V
400
VO = 3.3 V
700
600
500
VO = 1.8 V
VO = 1.05 V
400
300
200
100
0
0
5
10
15
20
VIN ± Input Voltage (V)
25
0.0
0.5
Figure 9. SWITCHING FREQUENCY vs
INPUT VOLTAGE (IO = 1 A)
1.0
1.5
IOUT ± Output Current (A)
C007
2.0
C008
Figure 10. SWITCHING FREQUENCY vs OUTPUT CURRENT
0.780
IOUT = 1 A
Vo = 1.05 V
VFB Voltage (V)
0.775
Vo (10 mV/div)
0.770
0.765
SW (5 V/div)
0.760
0.755
400 ns/div
0.750
±50
0
50
100
150
TJ ± Junction Temperature (ƒC)
C009
Figure 11. VFB VOLTAGE vs JUNCTION
TEMPERATURE (IO = 1 A)
Figure 12. VOLTAGE RIPPLE AT OUTPUT (IO = 2 A)
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
9
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
TYPICAL CHARACTERISTICS (continued)
VIN = 12 V, TA = 25°C (unless otherwise noted).
Vo = 1.05 V
VIN (50 mV/div)
SW (5 V/div)
400 ns/div
Figure 13. VOLTAGE RIPPLE AT INPUT (IO = 2 A)
10
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
DESIGN GUIDE
Step-By-Step Design Procedure
To
•
•
•
•
•
begin the design process, the user must know a few application parameters:
Input voltage range
Output voltage
Output current
Output voltage ripple
Input voltage ripple
VIN
4.5 to 23V
VIN
C1
10μF
C2
C3
10μF
0.1μF
U1
TPS54239DDA
R3 10.0kΩ
7
EN
5
VOUT
R1 8.25kΩ
6
R2
22.1kΩ
1
C4
8
C5
0.47μF
C6
8200pF
EN
VIN
VFB
VBST
VREG5
SW
SS
GND
2
1
C7 0.1μF
3
4
PwrPAD
9
1
VOUT
1.05V 2A
L1
VOUT
2.2μH
C8
C9
C10
22μF
22μF
1
Not Installed
Figure 14. Shows the schematic diagram for this design example.
Output Voltage Resistors Selection
The output voltage is set with a resistor divider from the output node to the VFB pin. It is recommended to use
1% tolerance or better divider resistors. Start by using Equation 2 to calculate VOUT.
To improve efficiency at light loads consider using larger value resistors, high resistance is more susceptible to
noise, and the voltage errors from the VFB input current are more noticeable.
V
= 0.765 x
OUT
æ
ö
çç1 + R1÷÷
÷
çè
R2 ø
(2)
Output Filter Selection
The output filter used with the TPS54239 is an LC circuit. This LC filter has double pole at:
F =
P
2p L
1
OUT
x COUT
(3)
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
11
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54239. 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 1
Table 1. Recommended Component Values
Output
Voltage
(V)
(1)
C4 (pF) (1)
R1 (kΩ) R2 (kΩ)
L1 (µH)
C8 + C9 + C10 (µF)
Min
Typ
Max
Min
Typ
Max
Min
Max
1
6.81
22.1
5
150
220
1.5
2.2
4.7
22
68
1.05
8.25
22.1
5
150
220
1.5
2.2
4.7
22
68
1.2
12.7
22.1
5
100
1.5
2.2
4.7
22
68
1.5
21.5
22.1
5
68
1.5
2.2
4.7
22
68
1.8
30.1
22.1
5
22
2.2
3.3
4.7
22
68
2.5
49.9
22.1
5
22
2.2
3.3
4.7
22
68
3.3
73.2
22.1
5
22
2.2
3.3
4.7
22
68
5
124
22.1
5
22
3.3
4.7
22
68
6.5
165
22.1
5
22
3.3
4.7
22
68
Optional
Since the DC gain is dependent on the output voltage, the required inductor value increases as the output
voltage increases. Additional phase boost can be achieved by adding a feed forward capacitor (C4) in parallel
with R1. The amount of available phase boost is dependent on the output voltage. Higher output voltages will
allow greater phase boost.
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 600 kHz for
fSW.
Use 600 kHz for fSW. Make sure the chosen inductor is rated for the peak current of Equation 5 and the RMS
current of Equation 6.
VIN(MAX) - VOUT
VOUT
´
IlP -P =
VIN(MAX)
LO ´ ¦ SW
(4)
IlPEAK =IO +
IlP-P
2
ILO(RMS) = IO2
(5)
1
+ IlP -P2
12
(6)
For this design example, the calculated peak current is 2.38 A and the calculated RMS current is 2.01 A. The
inductor used is a TDK CLF7045T-2R2N with a peak current rating of 5.5 A and an RMS current rating of 4.3 A.
For high current designs, TDK SPM6530T-4R7M 4.7µH is also recommended. The SPM6530 series has a higher
current rating than the CLF7045 series.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54239 is intended for use
with ceramic or other low ESR capacitors. Recommended values range from 22µF to 68µF. 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 22µF output capacitors are used. The typical ESR is 2 mΩ each.
The calculated RMS current is 0.22 A and each output capacitor is rated for 4A.
12
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
TPS54239
www.ti.com
SLVSBT0 – JANUARY 2013
Input Capacitor Selection
The TPS54239 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 from pin 2 to ground is optional to provide additional high frequency filtering. The capacitor voltage
rating needs to be greater than the maximum input voltage.
Bootstrap Capacitor Selection
A 0.1 µF. ceramic capacitor must be connected between the VBST to SW pin for proper operation. It is
recommended to use a ceramic capacitor.
VREG5 Capacitor Selection
A 0.47 µF. ceramic capacitor must be connected between the VREG5 to GND pin for proper operation. It is
recommended to use a ceramic capacitor.
THERMAL INFORMATION
This 8-pin DDA 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 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, see the Technical Brief, PowerPAD™ Thermally Enhanced Package, Texas Instruments Literature No.
SLMA002 and Application Brief, PowerPAD™ Made Easy, Texas Instruments Literature No. SLMA004.
The exposed thermal pad dimensions for this package are shown in the following illustration.
8
5
Exposed Thermal Pad
2,40
1,65
1
3,10
2,65
4
Figure 15. Thermal Pad Dimensions
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
13
TPS54239
SLVSBT0 – JANUARY 2013
www.ti.com
LAYOUT CONSIDERATIONS
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 analog 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 to 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 analog ground
trace.
12. Providing sufficient via is preferable for VIN, SW and PGND connection.
13. VIN input bypass capacitor and VIN high frequency bypass capacitor must be placed as near as possible to
the device.
14. Performance based on four layer printed circuit board.
Additional
Thermal
Vias
VIN INPUT
BYPASS
CAPACITOR
SOFT
START
CAP
TO ENABLE
CONTROL
Connection to
POWER GROUND
on internal or
bottom layer
VIN
BOOST
CAPACITOR
VBST
SS
VIN
EN
SW
VREG5
VOUT
OUTPUT
INDUCTOR
OUTPUT
FILTER
CAPACITOR
GND
VIN INPUT
BYPASS
CAPACITOR
EXPOSED
POWERPAD
AREA
Additional
Thermal
Vias
POWER GROUND
BIAS
CAP
FEEDBACK
RESISTORS
VFB
ANALOG
GROUND
TRACE
Figure 16. PCB Layout
14
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: TPS54239
PACKAGE OPTION ADDENDUM
www.ti.com
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)
TPS54239DDA
ACTIVE SO PowerPAD
DDA
8
75
RoHS & Green
SN
Level-2-260C-1 YEAR
-40 to 85
54239
TPS54239DDAR
ACTIVE SO PowerPAD
DDA
8
2500
RoHS & Green
SN
Level-2-260C-1 YEAR
-40 to 85
54239
(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
工商网监
湘ICP备2023018690号
