TPS54326
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SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
4.5V to 18V Input, 3-A Synchronous Step-Down Converter with Eco-mode™
Check for Samples: TPS54326
FEATURES
DESCRIPTION
•
The TPS54326 is an adaptive on-time D-CAP2™
mode synchronous buck converter. The TPS54326
enables system designers to complete the suite of
various end equipment’s power bus regulators with a
cost effective, low component count, low standby
current solution. The main control loop for the
TPS54326 uses the D-CAP2™ mode control which
provides a fast transient response with no external
components. The adoptive on-time control supports
seamless operation between PWM mode at heavy
load condition and reduced frequency Eco-mode™
operation at light load for high efficiency.
1
23
•
•
•
•
•
•
•
•
•
•
•
•
•
D-CAP2™ Mode Enables Fast Transient
Response
Low Output Ripple and Allows Ceramic Output
Capacitor
Wide VCC Input Voltage Range: 4.5 V to 18 V
Wide VIN Input Voltage Range: 2 V to 18 V
Output Voltage Range: 0.76 V to 5.5 V
Highly Efficient Integrated FET’s Optimized
for Lower Duty Cycle Applications
- 120 mΩ (High Side) and 70 mΩ (Low Side)
High Efficiency, less than 10 μA at Shutdown
Auto-Skip Eco-mode™ for High Efficiency at
Light Load
High Initial Bandgap Reference Accuracy
Adjustable Soft Start
Pre-Biased Soft Start
700-kHz Switching Frequency (fSW)
Cycle-By-Cycle Overcurrent Limit
Power Good Output
The TPS54326 also has a proprietary circuit that
enables the device to adapt to both low equivalent
series resistance (ESR) output capacitors, such as
POSCAP or SP-CAP, and ultra-low ESR ceramic
capacitors. The device operates from 4.5-V to 18-V
VCC input , and from 2-V to 18-V VIN input power
supply voltage. The output voltage can be
programmed between 0.76 V and 5.5 V. The device
also features an adjustable slow start time and a
power good function. The TPS54326 is available in
the 14 pin HTSSOP or 16 pin QFN package, and
designed to operate from –40°C to 85°C.
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)
VOUT (50 mV/div)
IOUT (1 A/div)
100 ms/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, Eco-mode, PowerPAD are trademarks 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 © 2009–2012, Texas Instruments Incorporated
TPS54326
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
ORDERING INFORMATION (1)
PACKAGE (2)
TA
(3)
ORDERABLE PART NUMBER
TPS54326PWP
PowerPAD™
(HTSSOP) – PWP
TPS54326RGTT
Plastic Quad Flat Pack (QFN)
(1)
(2)
(3)
Tube
14
TPS54326PWPR
–40°C to 85°C
TRANSPORT
MEDIA
PIN
Tape and Reel
Tape and Reel
16
TPS54326RGTR
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)
VI
Input voltage range
(1)
VALUE
UNIT
VIN, VCC, EN
–0.3 to 20
V
VBST
–0.3 to 26
V
VBST (vs SW1, SW2)
–0.3 to 6.5
V
VFB, VO, SS, PG
–0.3 to 6.5
V
–2 to 20
V
SW1, SW2
SW1, SW2 (10 ns transient)
VO
Output voltage range
Vdiff
Voltage from GND to POWERPAD
–3 to 20
V
VREG5
–0.3 to 6.5
V
PGND1, PGND2
–0.3 to 0.3
V
–0.2 to 0.2
V
2
kV
Human Body Model (HBM)
ESD rating Electrostatic discharge
500
V
TJ
Operating junction temperature
–40 to 150
°C
Tstg
Storage temperature
–55 to 150
°C
(1)
Charged Device Model (CDM)
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
TPS54326
THERMAL METRIC
(1)
TPS54326
PWP
RGT
14 PINS
16 PINS
θJA
Junction-to-ambient thermal resistance
55.6
46.1
θJCtop
Junction-to-case (top) thermal resistance
51.3
58.1
θJB
Junction-to-board thermal resistance
26.4
18.8
ψJT
Junction-to-top characterization parameter
1.8
1.3
ψJB
Junction-to-board characterization parameter
20.6
18.8
θJCbot
Junction-to-case (bottom) thermal resistance
4.3
4.8
(1)
UNITS
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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RECOMMENDED OPERATING CONDITIONS
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
VCC
Supply input voltage range
4.5
18
V
VIN
Power input voltage range
2
18
V
VBST
–0.1
24
VBST (vs SW1, SW2)
–0.1
5.7
SS, PG
–0.1
5.7
EN
–0.1
18
VO, VFB
–0.1
5.5
SW1, SW2
–1.8
18
VI
Input voltage range
SW1, SW2 (10 ns transient)
–3
18
PGND1, PGND2
–0.1
0.1
V
VO
Output voltage range
VREG5
–0.1
5.7
V
IO
Output current range
IVREG5
0
10
mA
TA
Operating free-air temperature
–40
85
°C
TJ
Operating junction temperature
–40
125
°C
ELECTRICAL CHARACTERISTICS
over operating free-air temperature range, VCC, VIN = 12V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CURRENT
IVCC
Operating - non-switching supply
current
VCC current, TA = 25°C, EN = 5 V,
VFB = 0.8 V
850
1300
μA
IVCCSDN
Shutdown supply current
VCC current, TA = 25°C, EN = 0 V
1.8
10
μA
LOGIC THRESHOLD
VENH
EN high-level input voltage
EN
VENL
EN low-level input voltage
EN
1.5
V
0.4
V
VFB VOLTAGE AND DISCHARGE RESISTANCE
VFB
Voltage light load mode
TA = 25°C, VO = 1.05 V, IO = 10 mA
TA = 25°C, VO = 1.05 V
Threshold voltage, continuous mode TA = 0°C to 85°C, VO = 1.05 V (1)
VFB
771
757
TA = -40°C to 85°C, VO = 1.05 V
(1)
IVFB
Input current
VFB = 0.8 V, TA = 25°C
RDischg
VO discharge resistance
EN = 0 V, VO = 0.5 V, TA = 25°C
765
753
mV
773
777
751
mV
779
0
±0.1
μA
50
100
Ω
5.5
5.7
V
20
mV
100
mV
VREG5 OUTPUT
VVREG5
Output voltage
TA = 25°C, 6 V < VCC < 18 V,
0 < IVREG5 < 5 mA
VLN5
Line regulation
6 V < VCC < 18 V, IVREG5 = 5 mA
VLD5
Load regulation
0 mA < IVREG5 < 5 mA
IVREG5
Output current
VCC = 6 V, VREG5 = 4 V, TA = 25°C
RDS(on)h
High side switch resistance
25°C, VBST - SW1, SW2 = 5.5 V
RDS(on)l
Low side switch resistance
25°C
5.3
70
mA
120
mΩ
70
mΩ
MOSFET
CURRENT LIMIT
Iocl
Current limit
LOUT = 1.5µH
(1)
3.5
4.1
5.5
A
THERMAL SHUTDOWN
TSDN
(1)
Thermal shutdown threshold
Shutdown temperature
Hysteresis
(1)
(1)
150
25
°C
Specified by Design (not production tested).
3
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ELECTRICAL CHARACTERISTICS (continued)
over operating free-air temperature range, VCC, VIN = 12V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ON-TIME TIMER CONTROL
tON
On time
VIN = 12 V, VO = 1.05 V
145
tOFF(MIN)
Minimum off time
TA = 25°C, VFB = 0.7 V
260
310
ns
2.6
ns
SOFT START
ISSC
SS charge current
VSS = 0 V
1.4
2
ISSD
SS discharge current
VSS = 0.5 V
0.1
0.2
VFB rising (good)
85
90
μA
mA
POWER GOOD
VTHPG
Threshold
IPG
Sink current
VFB falling (fault)
95
85
PG = 0.5 V
2.5
5
115
120
%
mA
OUTPUT UNDERVOLTAGE AND OVERVOLTAGE PROTECTION
VOVP
Output OVP trip threshold
tOVPDEL
Output OVP prop delay
VUVP
Output UVP trip threshold
tUVPDEL
Output UVP delay
tUVPEN
Output UVP enable delay
OVP detect
125
UVP detect
65
Hysteresis
70
75
10
0.25
Relative to soft-start time
%
μs
5
%
ms
x 1.7
UVLO
UVLO
Threshold
Wake up VREG5 voltage
3.55
3.8
4.05
Hysteresis VREG5 voltage
0.23
0.35
0.47
V
DEVICE INFORMATION
PWP PACKAGE
(TOP VIEW)
VO
1
14
VCC
VFB
2
13
VIN
VREG5
3
12
VBST
SS
4
11
SW2
GND
5
10
SW1
PG
6
9
PGND2
EN
7
8
PGND1
POWERPAD
4
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VFB
VREG5
VO
VCC
VIN2
VIN1
RGT PACKAGE
(TOP VIEW)
16
15
14
13
1
2
12
VBST
11
SW3
EXPOSED
THERMAL
PAD
SW2
GND
4
9
SW1
PG
5
6
7
8
PGND2
10
PGND1
3
EN
SS
PIN FUNCTIONS
PIN
NAME
DESCRIPTION
PWP 14
RGT 16
VO
1
16
Connect to output of converter. This pin is used for On-Time Adjustment.
VFB
2
1
Converter feedback input. Connect with feedback resistor divider.
VREG5
3
2
5.5 V power supply output. A capacitor (typical 1μF) should be connected to GND.
SS
4
3
Soft-start control. A external capacitor should be connected to GND.
GND
5
4
Signal ground pin
PG
6
5
Open drain power good output
EN
7
6
Enable control input
8, 9
7, 8
10, 11
9, 10, 11
VBST
12
12
VIN
13
13, 14
VCC
14
15
Back
side
Back
side
PGND1,
PGND2
SW1, SW2
Exposed
Thermal
Pad or
PowerPAD
™
Ground returns for low-side MOSFET. Also serve as inputs of current comparators. Connect PGND
and GND strongly together near the IC.
Switch node connection between high-side NFET and low-side NFET. Also serve as inputs to current
comparators.
Supply input for high-side NFET gate driver (boost terminal). Connect capacitor from this pin to
respective SW1, SW2 terminals. An internal PN diode is connected between VREG5 to VBST pin.
Power input and connected to high side NFET drain
Supply input for 5 V internal linear regulator for the control circuitry
Thermal pad of the package. Must be soldered to achieve appropriate dissipation. Should be
connected to PGND.
5
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Functional Block Diagram
-30%
UV
14
VO
VIN
VIN
OV
1
VCC
13
+20%
VREG5
12
Control logic
VBST
Ref
SS
1 shot
SW
VFB
SGND
10
XCON
VREG5
VREG5
Ceramic
Capacitor
3
1 mF
VO
11
2
SS
9
4
8
SW
Softstart
ZC
SS
PGND
5
PGND
PGND
GND
SW
OCP
SGND
PG
Ref
6
PGND
VCC
-10%
UV
VREG5
EN
7
A.
EN
Logic
OV
UVLO
UVLO
Protection
Logic
TSD
REF
Ref
Block diagram shown is for PWP 14 pin package. QFN 16 pin package block diagram is identical except for pin out.
OVERVIEW
The TPS54326 is a 3-A synchronous step-down (buck) converter with two integrated N-channel MOSFETs and
Auto-Skip Eco-Mode™ to improve light lode efficiency . 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 TPS54326 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.
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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 timer 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 the 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
TPS54326 uses an adaptive on-time control scheme and does not have a dedicated on board oscillator. The
TPS54326 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. The actual frequency may vary from 700 kHz depending on the off time, which is ended when the
fed back portion of the output voltage falls to the VFBthreshold voltage.
Auto-Skip Eco-Mode™ Control
The TPS54326 is designed with Auto-Skip Eco-Mode™ to increase light load efficiency. As the output current
decreases from heavy load condition, the inductor current is also reduced and eventually comes to point that its
rippled valley touches zero level, which is the boundary between continuous conduction and discontinuous
conduction modes. The rectifying MOSFET is turned off when its zero inductor current is detected. As the load
current further decreases the converter run into discontinuous conduction mode. The on-time is kept almost the
same as is was in the continuous conduction mode so that it takes longer time to discharge the output capacitor
with smaller load current to the level of the reference voltage. The transition point to the light load operation
IOUT(LL) current can be calculated in Equation 1.
1
(VIN - VOUT) · VOUT
IOUT(LL) = - ·2 · L · fws
VIN
(1)
Soft Start and Pre-Biased 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 2. VFB voltage is 0.765 V and SS pin source current is
2 μA.
C6(nF) • Vref
C6(nF) • 0.765
Tss(ms) = − = −
Iss(µA)
2
(2)
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-by-cycle 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.
Power Good
The power good function is activated after soft start has finished. The power good function becomes active after
1.7 times soft-start time. When the output voltage is within –10% of the target value, internal comparators detect
power good state and the power good signal becomes high. Rpg resister value, which is connected between PG
and VREG5, is required from 20kΩ to 150kΩ. If the feedback voltage goes under 15% of the target value, the
power good signal becomes low after a 10 ms internal delay.
Output Discharge Control
TPS54326 discharges the output when EN is low, or the controller is turned off by the protection functions (OVP,
UVP, UVLO and thermal shutdown). The output is discharged by an internal 50-Ω MOSFET which is connected
from VO to PGND. The internal low-side MOSFET is not turned on during the output discharge operation to
avoid the possibility of causing negative voltage at the output.
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Current Protection
The output over-current 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. If the measured voltage is
above the voltage proportional to the current limit, Then , the device constantly monitors the low-side FET switch
voltage, which is proportional to the switch current, during the low-side on-time.
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.
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 under-voltage protection circuit to be activated. When the over current
condition is removed, the output voltage will return to the regulated value. This protection is non-latching.
Over/Undervoltage Protection
The TPS54326 detects over and undervoltage conditions by monitoring the feedback voltage (VFB). This
function is enabled after approximately 1.7 times the soft-start time. When the feedback voltage becomes higher
than 120% of the target voltage, the OVP comparator output goes high and the circuit latches the high-side
MOSFET driver turns off and the low-side MOSFET turns on. When the feedback voltage becomes lower than
70% of the target voltage, the UVP comparator output goes high and an internal UVP delay counter begins. After
250 μs, the device latches off both internal top and bottom MOSFET.
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 TPS54326 is shut off. This is protection is non-latching.
Thermal Shutdown
Thermal protection is self-activating. If the junction temperature exceeds the threshold value (typically 150°C),
the TPS54326 shuts off. This protection is non-latching.
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TYPICAL CHARACTERISTICS
VIN = 12 V, TA = 25°C (unless otherwise noted)
spacer
1200
8
1000
Shutdown Current - mA
Supply Current - mA
6
800
600
400
4
2
200
0
-50
0
50
100
TJ - Junction Temperature - °C
0
-50
150
Figure 1. VCC SUPPLY CURRENT vs. JUNCTION
TEMPERATURE
50
100
TJ - Junction Temperature - °C
150
Figure 2. VCC SHUTDOWN CURRENT vs. JUNCTION
TEMPERATURE
1.1
1.1
1.075
1.05
VI = 12 V
IO = 10 mA
1.075
VI = 18 V
VO - Output Voltage - V
VO - Output Voltage - V
0
VI = 5 V
1.05
IO = 1 mA
1.025
1.025
1
1
0
0.5
1
1.5
2
IO - Output Current - A
2.5
Figure 3. 1.05-V OUTPUT VOLTAGE vs. OUTPUT
CURRENT
3
0
5
10
VI - Input Voltage - V
15
20
Figure 4. 1.05-V OUTPUT VOLTAGE vs. INPUT VOLTAGE
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TYPICAL CHARACTERISTICS (continued)
VIN = 12 V, TA = 25°C (unless otherwise noted)
spacer
VOUT (50 mV/div)
EN (10 V/div)
VOUT (0.5 V/div)
IOUT (1 A/div)
PG (5 V/div)
100 ms/div
400 ms/div
Figure 5. 1.05-V, 0-A TO 3-A LOAD TRANSIERESPONSE
Figure 6. START-UP WAVE FORM
100
100
VO = 3.3 V
VO = 3.3 V
20
80
VO = 1.8 V
VO = 2.5 V
Efficiency - %
Efficiency - %
80
60
VO = 1.8 V
60
VO = 2.5
40
40
20
20
0
0
0.5
1
1.5
2
IO - Output Current - A
2.5
Figure 7. EFFICIENCY vs. OUTPUT CURRENT
(VIN = 12 V)
3
0
0.001
0.01
IO - Output Current - A
0.1
Figure 8. LIGHT LOAD EFFICIENCY vs. OUTPUT
CURRENT
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TYPICAL CHARACTERISTICS (continued)
VIN = 12 V, TA = 25°C (unless otherwise noted)
spacer
900
900
800
VO = 1.8 V
fsw - Switching Frequency - kHz
fsw - Switching Frequency - kHz
700
800
600
VO = 1.8 V
VO = 2.5 V
500
700
400
300
VO = 3.3 V
600
200
100
500
0
5
10
VI - Input Voltage - V
15
20
Figure 9. SWITCHING FREQUENCY vs INPUT VOLTAGE
0
0.001
0.01
IO - Output Current - A
0.1
Figure 10. SWITCHING FREQUENCY vs OUTPUT
CURRENT
VIN (50 mV/div)
VO (10 mV/div)
SW (5 V/div)
SW (5 V/div)
400 ns/div
400 ns/div
Figure 11. VOLTAGE RIPPLE At OUTPUT
Figure 12. VOLTAGE RIPPLE At INPUT
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DESIGN GUIDE
Step By Step Design Procedure
To
•
•
•
•
•
begin the design process, the following application parameters must be known:
Input voltage range
Output voltage
Output current
Output voltage ripple
Input voltage ripple
Figure 13 shows the schematic diagram for this design example.
Figure 13. Schematic Diagram
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 3 and Equation 4 to calculate VOUT.
To improve efficiency at light loads consider using larger value resistors, too high of resistance is more
susceptible to noise and voltage errors from the VFB input current are more noticeable.
For output voltage from 0.76 V to 2.5 V:
(
R1
VOUT = 0.765 • 1 + −
R2
)
(3)
For output voltage over 2.5 V:
(
R1
VOUT = (0.763 + 0.0017 • VOUT) • 1 + −
R2
)
(4)
Where:
VOUT_SET = Target VOUT voltage
12
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
TPS54326
www.ti.com
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
Output Filter Selection
The output filter used with the TPS54326 is an LC circuit. This LC filter has double pole at:
FP =
1
2p LOUT ´ COUT
(5)
At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal
gain of the TPS54326. 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 5 is located below the high frequency zero but close enough that the phase boost provided by 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)
R1 (kΩ)
R2 (kΩ)
(1)
C4 (pF) (1)
L1 (µH)
C4 + C5 (µF)
1
6.81
22.1
1.5
22 - 68
1.05
8.25
22.1
1.5
22 - 68
1.2
12.7
22.1
1.5
22 - 68
1.8
30.1
22.1
10 - 47
2.2
22 - 68
2.5
49.9
22.1
10 - 47
2.2
22 - 68
3.3
73.2
22.1
10 - 47
2.2
22 - 68
5
121
22.1
10 - 47
3.3
22 - 68
Optional
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 6,
Equation 7, and Equation 8. 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.
VOUT VIN (max) - VOUT
•
Ilp - p = V
L •f
IN (max)
O
(6)
SW
Ilp - p
Ilpeak = IO +
2
−
1 Ilp - p2
ILo(RMS) = IO2 + −
12
(7)
√
(8)
For this design example, the calculated peak current is 3.47 A and the calculated RMS current is 3.01 A. The
inductor used is a TDK SPM6530-1R5M100 with a peak current rating of 11.5 A and an RMS current rating of 11
A.
The capacitor value and ESR determines the amount of output voltage ripple. The TPS54326 is intended for use
with ceramic or other low ESR capacitors. Recommended values range from 22 µF to 68 µF. Use Equation 9 to
determine the required RMS current rating for the output capacitor.
VOUT • (VIN - VOUT)
ICO(RMS) =−
−
√12 • VIN • LO • fSW
(9)
For this design two TDK C3216X5R0J226M 22 µF output capacitors are used. The typical ESR is 2 mΩ each.
The calculated RMS current is 0.271 A and each output capacitor is rated for 4 A.
13
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
TPS54326
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
www.ti.com
Input Capacitor Selection
The TPS54326 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 14 to ground is recommended. 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 1.0 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
The PWP 14 pin package incorporates an exposed PowerPAD™ and the QFN 16 pin package incorporates a
similar exposed thermal pad. These exposed thermal pads are designed to be connected to an external heatsink.
The thermal pad must be soldered directly to the printed board (PCB). After soldering, the PCB can be used as a
heatsink. 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
heatsink structure designed into the PCB. This design optimizes the heat transfer from the integrated circuit (IC).
For additional information on the PowerPAD™ package 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 the PWP 14 pin and QFN 16 pin packages are shown in the Thermal
Pad Mechanical Data section of this data sheet.
14
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
TPS54326
www.ti.com
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
LAYOUT CONSIDERATIONS
The following layout guidelines are provided using the PWP 14 pin package as an example. The general
guidelines and routing are also applicable to the QFN 16 pin package. Allowance should be made for the
differences in the package pin configurations.
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. If VIN and VCC is shorted, VIN and VCC patterns need to be connected with broad pattern lines.
15. VIN Capacitor should be placed as near as possible to the device.
Additional
Thermal
Vias
FEEDBACK
RESISTORS
BIAS
CAP
Connection to
POWER GROUND
on internal or
bottom layer
SLOW
START
CAP
ANALOG
GROUND
TRACE
To Enable
Control
VCC
INPUT
BYPASS
CAPACITOR
VCC
VOUT
VCC
VFB
VIN
VREG5
VBST
SS
SW1
GND
SW2
PG
PGND1
EN
EXPOSED
POWERPAD
AREA
VIN
VIN
INPUT
BYPASS
CAPACITOR
BOOST
CAPACITOR
OUTPUT
INDUCTOR
PGND2
VOUT
OUTPUT
FILTER
CAPACITOR
Additional
Thermal
Vias
POWER GROUND
VIA to Ground Plane
Etch on Bottom Layer
or Under Component
Figure 14. TPS54326 Layout
15
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
TPS54326
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
www.ti.com
REVISION HISTORY
Changes from Original (October 2009) to Revision A
•
Page
Changed the data sheet From: Product Preview To: Production Data ................................................................................ 1
Changes from Revision A (October 2009) to Revision B
Page
•
Changed the title to include Eco-Mode ................................................................................................................................. 1
•
Changed features bullet to reference Eco-mode .................................................................................................................. 1
•
Added Eco-Mode text to the DESCRIPTION ....................................................................................................................... 1
•
Added the QFN package to the DESCRIPTION .................................................................................................................. 1
•
Added the QFN package to the ORDERING INFORMATION table .................................................................................... 2
•
Added the RGT PACKAGE drawing ..................................................................................................................................... 5
•
Added the RGT 16 pin column to the PIN FUNCTIONS table ............................................................................................. 5
•
Changed Functional Block Diagram ..................................................................................................................................... 6
•
Added text Note to the Functional Block Diagram ................................................................................................................ 6
•
Added Eco-Mode text to the OVERVIEW section ................................................................................................................ 6
•
Changed section title From: Light Load Mode Control To: Light Load Eco-Mode Control ................................................... 7
•
Added Eco-Mode to text in Light Load Eco-Mode Control section ....................................................................................... 7
•
Added Note 1 to Table 1 ..................................................................................................................................................... 13
•
Added text to the THERMAL INFORMATION section for the QFN package. .................................................................... 14
•
Deleted figure "Thermal Pad Dimensions" ......................................................................................................................... 14
Changes from Revision B (June 2010) to Revision C
Page
•
Changed TPS54326PWPR tape and reel quantity From: 3000 To: 2000 ............................................................................ 2
•
Added VCC, VIN = 12V to the condition statement in the Electrical Characteristics table ..................................................... 3
Changes from Revision C (October 2010) to Revision D
Page
•
Deleted quantities from Transport Media column ................................................................................................................. 2
•
Changed from –45°C to 85°C to –40°C to 85°C in Ordering Information ............................................................................ 2
•
Added Thermal Information table ......................................................................................................................................... 2
•
Added IO row to the ROC table ............................................................................................................................................. 3
•
Changed Functional Block Diagram ..................................................................................................................................... 6
•
Changed section title From: Light Load Eco-Mode Control To: Auto-Skip Eco-Mode Control ............................................. 7
•
Added Auto-Skip to text in Auto-Skip Eco-Mode Control section ......................................................................................... 7
•
Changed Equation 1 ............................................................................................................................................................. 7
•
Changed Power Good section text ....................................................................................................................................... 7
•
Changed Current Protection section text .............................................................................................................................. 8
•
Changed Design Guide information .................................................................................................................................... 12
•
Changed Table 1 C4 values ............................................................................................................................................... 13
16
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
TPS54326
www.ti.com
SLVSA13E – OCTOBER 2009 – REVISED JUNE 2012
Changes from Revision D (February 2011) to Revision E
Page
•
Removed SWIFT from the data sheet tilte ........................................................................................................................... 1
•
Changed VENH min value in ELECTRICAL CHARACTERISTICS from 2 V to 1.5 V ............................................................ 3
•
Changed Table 1 last column heading from C8 + C9 to C4 + C5 ...................................................................................... 13
•
Deleted text from the Input Capacitor Selection setion - "to improve the stability of the over-current limit function." ........ 14
17
Copyright © 2009–2012, Texas Instruments Incorporated
Product Folder Link(s) :TPS54326
PACKAGE OPTION ADDENDUM
www.ti.com
11-Aug-2022
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)
Samples
(4/5)
(6)
TPS54326PWP
ACTIVE
HTSSOP
PWP
14
90
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
PS54326
Samples
TPS54326PWPR
ACTIVE
HTSSOP
PWP
14
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
PS54326
Samples
TPS54326RGTR
ACTIVE
VQFN
RGT
16
3000
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
54326
Samples
TPS54326RGTT
ACTIVE
VQFN
RGT
16
250
RoHS & Green
NIPDAU
Level-1-260C-UNLIM
-40 to 85
54326
Samples
(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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