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TPS62125
SLVSAQ5E – MARCH 2012 – REVISED MAY 2017
TPS62125 3-V to 17-V, 300-mA Step-Down Converter With Adjustable Enable Threshold
and Hysteresis
1 Features
3 Description
•
•
The TPS62125 device is a high-efficiency
synchronous step-down converter optimized for low
and ultralow power applications providing up to 300mA output current. The wide input voltage range of 3
V to 17 V supports 4-cell alkaline and 1- to 4-cell LiIon batteries in series configuration as well as 9-V to
15-V powered applications. The device includes a
precise low-power enable comparator which can be
used as an input supply voltage supervisor (SVS) to
address system specific power-up and power-down
requirements. The enable comparator consumes only
6-µA quiescent current and features an accurate
threshold of 1.2 V typical as well as an adjustable
hysteresis. With this feature, the converter can
generate a power supply rail by extracting energy
from a storage capacitor fed from high impedance
sources such as solar panels or current loops. With
its DCS-Control scheme the converter provides
power-save mode operation to maintain highest
efficiency over the entire load current range. At light
loads the converter operates in pulse frequency
modulation (PFM) mode and transitions seamlessly
and automatically in pulse width modulation (PWM)
mode at higher load currents. The DCS-Control™
scheme is optimized for low-output ripple voltage in
PFM mode in order to reduce output noise to a
minimum and features excellent AC load regulation.
An open-drain power good output indicates once the
output voltage is in regulation.
1
•
•
•
•
•
•
•
•
•
•
•
•
•
Wide Input Voltage Range 3 V to 17 V
Input Supply Voltage Supervisor (SVS) With
Adjustable Threshold and Hysteresis Consuming
Typical 6-µA Quiescent Current
Wide Output Voltage Range 1.2 V to 10 V
Typical 13-µA Quiescent Current
350-nA Typical Shutdown Current
Seamless Power Save Mode Transition
DCS-Control™ Scheme
Low Output Ripple Voltage
Up to 1-MHz Switching Frequency
Highest Efficiency over Wide VIN and VOUT Range
Pin to Pin Compatible with TPS62160/70
100% Duty Cycle Mode
Power Good Open Drain Output
Output Discharge Function
Small 2-mm × 2-mm 8-pin WSON Package
2 Applications
•
•
•
•
•
Embedded Processing
4-Cell Alkaline, 1- to 4-Cell Li-Ion Battery-Powered
Applications
9-V to 15-V Standby Power Supply
Energy Harvesting
Inverter (Negative VOUT)
Device Information(1)
PART NUMBER
PACKAGE
TPS62125
BODY SIZE (NOM)
WSON (8)
2.00 mm × 2.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Schematic
TPS62125
VIN
L 15µH
SW
R1
1.8M
VOS
CIN
10µF
EN
FB
R2
576k
EN_hys
Rpullup
GND
PG
10mA
100mA
90
PWR GOOD
COUT
10µF
85
250mA
1.0mA
80
Efficiency (%)
VIN = 4V to 17V
Efficiency vs Input Voltage
95
VOUT = 3.3V
up to 300mA
75
70
0.25mA
65
VOUT = 3.3V
L = 15mH VLF302515
COUT = 10mF
60
0.1mA
55
50
4
5
6
7
8
9
10 11
12 13 14 15 16 17
Input Voltage VIN(V)
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.
TPS62125
SLVSAQ5E – MARCH 2012 – REVISED MAY 2017
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
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 9
7.1
7.2
7.3
7.4
Overview ................................................................... 9
Functional Block Diagram ......................................... 9
Feature Description................................................. 10
Device Functional Modes........................................ 10
8
Application and Implementation ........................ 13
8.1 Application Information............................................ 13
8.2 Typical Application .................................................. 13
8.3 System Examples .................................................. 26
9 Power Supply Recommendations...................... 28
10 Layout................................................................... 28
10.1 Layout Guidelines ................................................. 28
10.2 Layout Example .................................................... 28
11 Device and Documentation Support ................. 29
11.1
11.2
11.3
11.4
11.5
11.6
Device Support......................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
29
29
29
29
29
29
12 Mechanical, Packaging, and Orderable
Information ........................................................... 29
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision D (July 2015) to Revision E
•
Added SW node AC abs max ratings .................................................................................................................................... 4
Changes from Revision C (December 2013) to Revision D
•
2
Page
Page
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
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SLVSAQ5E – MARCH 2012 – REVISED MAY 2017
5 Pin Configuration and Functions
DSG Package
8-Pin WSON
Top View
8
1
2
3
TH E
ER XP
M OS
A ED
L
PA
D
GND
VIN
EN
EN_hys
4
7
6
5
PG
SW
VOS
FB
Pin Functions
PIN
NAME
EN
NO.
3
I/O
IN
DESCRIPTION
Input pin for the enable comparator. Pulling this pin to GND turns the device into shutdown mode.
The DC/DC converter is enabled once the rising voltage on this pin trips the enable comparator
threshold, VTH EN ON of typ. 1.2 V. The DC/DC converter is turned off once a falling voltage on this
pin trips the threshold, VTH EN OFF of typ. 1.15 V. The comparator threshold can be increased by
connecting an external resistor to pin EN_hys. See also application section. This pin must be
terminated.
EN_hys
4
OUT
Enable hysteresis open-drain output. This pin is pulled to GND when the voltage on the EN pin is
below the comparator threshold VTH EN ON of typ. 1.2 V and the comparator has not yet tripped. The
pin is high impedance once the enable comparator has tripped and the voltage at the pin EN is
above the threshold VTH EN ON. The pin is pulled to GND once the falling voltage on the EN pin trips
the threshold VTH EN OFF (1.15 V typical). This pin can be used to increase the hysteresis of the
enable comparator. If not used, tie this pin to GND, or leave it open.
FB
5
IN
This is the feedback pin for the regulator. An external resistor divider network connected to this pin
sets the output voltage. In case of fixed output voltage option, the resistor divider is integrated and
the pin need to be connected directly to the output voltage.
GND
1
PWR
GND supply pin.
PG
8
OUT
Open drain power good output. This pin is internally pulled to GND when the device is disabled or
the output voltage is below the PG threshold. The pin is floating when the output voltage is in
regulation and above the PG threshold. For power good indication, the pin can be connected via a
pull up resistor to a voltage rail up to 10 . The pin can sink a current up to 0.4 mA and maintain the
specified high/low voltage levels. It can be used to discharge the output capacitor with up to 10 mA.
In this case the current into the pin must be limited with an appropriate pull up resistor. More details
can be found in the application section. If not used, leave the pin open, or connect to GND.
SW
7
OUT
This is the switch pin and is connected to the internal MOSFET switches. Connect the inductor to
this pin. Do not tie this pin to VIN, VOUT or GND.
VIN
2
PWR
VIN power supply pin.
VOS
6
IN
This is the output voltage sense pin for the DCS-Control circuitry. This pin must be connected to the
output voltage of the DC/DC converter.
Exposed
Thermal PAD
–
–
This pad must be connected to GND.
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6 Specifications
6.1 Absolute Maximum Ratings
Pin voltage (2)
MIN
MAX
UNIT
VIN
–0.3
20
V
SW (DC)
–0.3
VIN + 0.3V
V
SW (AC, less than 10ns) (3)
-3.0
23.5
V
EN
–0.3
VIN + 0.3
V
FB
–0.3
3.6
V
VOS, PG
–0.3
12
V
EN_hys
–0.3
7
V
10
mA
Power good sink
current
IPG
EN_hys sink current
IEN_hys
3
mA
Maximum operating junction temperature, TJ
–40
125
°C
Storage temperature, Tstg
–65
150
°C
(1)
(2)
(3)
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.
All voltage values are with respect to network ground terminal GND.
While switching
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1000
UNIT
V
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
MIN NOM MAX
VIN
Supply voltage
3
Output current capability
TA
Operating ambient temperature
TJ
Operating junction temperature,
(1)
(1)
3 V ≤ VIN < 6 V
200
6 V ≤ VIN ≤ 17 V
300
(Unless Otherwise Noted)
UNIT
17
V
mA
–40
85
°C
–40
125
°C
In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may
have to be derated. Maximum ambient temperature (TA(max)) is dependent on the maximum operating junction temperature (TJ(max)) and
the maximum power dissipation of the device in the application (PD(max)); for more information about traditional and new thermal metrics,
see the Semiconductor and IC Package Thermal Metrics application report.
6.4 Thermal Information
TPS62125
THERMAL METRIC
(1)
DSG (WSON)
UNIT
8 PINS
RθJA
Junction-to-ambient thermal resistance
65.2
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
93.3
°C/W
RθJB
Junction-to-board thermal resistance
30.1
°C/W
ψJT
Junction-to-top characterization parameter
0.5
°C/W
ψJB
Junction-to-board characterization parameter
47.4
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
7.2
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
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6.5 Electrical Characteristics
TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted), VIN = 12 V
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
UNIT
SUPPLY
VIN
Input voltage range (1)
3
17
V
VOUT
Output voltage range
1.2
10
V
23
µA
IQ
Quiescent current
IOUT = 0 mA, device not switching, EN = VIN,
regulator sleeps
13
IOUT = 0 mA, device switching, VIN = 7.2 V,
VOUT = 1.2 V, L = 22 µH
14
µA
VIN = 5 V, EN = 1.1 V, enable comparator active,
device DC/DC converter off
6
11
µA
IActive
Active mode current consumption
VIN = 5 V = VOUT, TA = 25°C, high-side MOSFET
switch fully turned on (100% mode)
230
275
µA
ISD
Shutdown current (2)
Enable comparator off, EN < 0.4 V,
VOUT = SW = 0 V, VIN = 5 V
0.35
2.4
µA
VUVLO
Undervoltage lockout threshold
Falling VIN
2.8
2.85
V
Rising VIN
2.9
2.95
V
1.16
1.20
1.24
V
1.12
1.15
1.19
ENABLE COMPARATOR THRESHOLD AND HYSTERESIS (EN, EN_hys)
VTH EN ON
EN pin threshold rising edge
VTH EN OFF
EN pin threshold falling edge
VTH EN Hys
EN pin hysteresis IN
IIN EN
Input bias current into EN pin
EN = 1.3 V
VEN_hyst
EN_hys pin output low
IEN_hyst = 1 mA, EN = 1.1 V
IIN EN_hyst
Input bias current into EN_hyst pin
EN_hyst = 1.3 V
3 V ≤ V≤ 17 V
50
0
0
V
mV
50
nA
0.4
V
50
nA
POWER SWITCH
High-side MOSFET ON-resistance
RDS(ON)
Low-side MOSFET ON-resistance
ILIMF
TSD
VIN = 3 V, I = 100 mA
2.4
4
VIN = 12 V, I = 100 mA
1.5
2.6
VIN = 3 V, I = 100 mA
0.75
1.3
VIN = 12 V, I = 100 mA
0.6
1
750
900
Ω
Switch current limit high-side
MOSFET
VIN = 12 V
Thermal shutdown
Increasing junction temperature
150
°C
Thermal shutdown hysteresis
Decreasing junction temperature
20
°C
500
ns
60
ns
0.808
V
600
mA
OUTPUT
tONmin
Minimum ON-time
VIN = 5 V, VOUT = 2.5 V
tOFFmin
Minimum OFF-time
VIN = 5 V
VREF_FB
Internal reference voltage of error
amplifier
VFB
Feedback voltage accuracy
Referred to internal reference (VREF_FB)
Feedback voltage line regulation
IOUT = 100 mA, 5 V ≤ VIN ≤ 17 V, VOUT = 3.3 V (3)
–2.5%
(3)
0% 2.5%
–0.05
%/V
–0.00
4
%/mA
Feedback voltage load regulation
VOUT = 3.3 V; IOUT = 1 mA to 300 mA, VIN = 12 V
Input bias current into FB pin
VFB = 0.8 V
tStart
Regulator start-up time
Time from EN high to device starts switching,
VIN = 5 V
tRamp
Output voltage ramp time
Time to ramp up VOUT = 1.8 V, no load
200
ILK_SW
Leakage current into SW pin (4)
2.85
µA
Bias current into VOS pin
VOS = VIN = VSW = 1.8 V, EN = GND, device in
shutdown mode
1.8
IIN_VOS
0
50
nA
IIN_FB
(1)
(2)
(3)
(4)
0
50
50
nA
µs
The part is functional down to the falling UVLO (Undervoltage Lockout) threshold
Current into VIN pin
VOUT = 3.3 V, L = 15 µH, COUT = 10 µF
An internal resistor divider network with typ. 1 MΩ total resistance is connected between SW pin and GND.
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Electrical Characteristics (continued)
TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted), VIN = 12 V
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
Rising VFB feedback voltage
93%
95%
97%
Falling VFB feedback voltage
87%
90%
93%
UNIT
POWER GOOD OUTPUT (PG)
VTH_PG
Power good threshold voltage
VOL
PG pin output low voltage
Current into PG pin IPG= 0.4 mA
0.3
VOH
PG pin output high voltage
Open drain output, external pullup resistor
10
V
IIN_PG
Bias current into PG pin
V(PG) = 3 V, EN = 1.3 V, FB = 0.85 V
50
nA
6
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6.6 Typical Characteristics
25
1.5
1.4
1.3
TA = 85°C
1.2
20
Quiescent Current IQ (mA)
Shutdown Current - ISD [mA]
1.1
TA = 60°C
1.0
0.9
TA = 25°C
0.8
TA = 0°C
0.7
0.6
TA = -40°C
0.5
IQ no switching: TA= 85°C
IQ no switching: TA= 60°C
15
IQ no switching: TA= 25°C
10
IQ no switching: TA= -40°C
0.4
IQ device switching: TA= 25°C,
VOUT = 1.8V, IOUT = 0mA no load,
EN = VIN
5
0.3
0.2
0.1
0
3
4
5
6
7
0
8 9 10 11 12 13 14 15 16 17
Input Voltage - VIN [V]
Figure 1. Shutdown Current vs. Input Voltage
3
4
5
6
7
8 9 10 11 12 13 14 15 16 17
Input Voltage (V)
Figure 2. Quiescent Current vs. Input Voltage
1000
25
VIN = 6V TA = 85°C
20
Quiescent Current (mA)
Quiescent Current (mA)
100
VIN = 6V TA = 25°C
VIN = 6V TA = 85°C
VIN = 6V TA = -40°C
VIN = 12V TA = 25°C
VIN = 12V TA = 85°C
VIN = 12V TA = −40°C
10
VIN = 12V TA = 85°C
VIN = 6V TA = 25°C
15
VIN = 12V TA = 25°C
VIN = 6V TA = -40°C
VIN = 12V TA = −40°C
10
1
5
0.1
0
200
400
600
800
1000
Voltage VEN (mV)
1200
0
200
400
600
800
1000
Voltage VEN (mV)
1200
1400
Figure 4. Quiescent Current vs. VEN Voltage, Falling VEN
3
2.8
2.6
2.4
VTH EN ON TA = 25°C
VTH EN ON TA = -40°C
2.2
VTH EN ON TA = 85°C
TA = 85°C
2
RDSON (W)
EN Comparator Threshold - VTH EN (V)
Figure 3. Quiescent Current vs. EN Voltage, Rising VEN
1.25
1.245
1.24
1.235
1.23
1.225
1.22
1.215
1.21
1.205
1.2
1.195
1.19
1.185
1.18
1.175
1.17
1.165
1.16
1.155
1.15
0
1400
TA = 60°C
1.8
1.6
1.4
1.2
1
VTH EN OFF TA = 25°C
VTH EN OFF TA = -40°C
VTH EN OFF TA = 85°C
TA = 0°C
TA = -40°C
0.8
TA = 25°C
0.6
0.4
0.2
0
3
4
5
6
7
8 9 10 11 12 13 14 15 16 17
Input Voltage VIN (V)
Figure 5. EN Comparator Thresholds vs. Input Voltage
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17
Input Voltage VIN [V]
Figure 6. RDSON High-Side Switch
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Typical Characteristics (continued)
1.0
0.9
TA = 85°C
0.8
TA = 60°C
0.7
RDSON (W)
0.6
0.5
0.4
TA = 0°C
0.3
TA = 25°C
TA = -40°C
0.2
0.1
0
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17
Input Voltage - VIN [V]
Figure 7. RDSON Low-Side Switch (Rectifier)
8
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7 Detailed Description
7.1 Overview
The TPS62125 high-efficiency synchronous switch mode buck converter includes TI's DCS-Control (Direct
Control with Seamless Transition into Power-Save Mode), an advanced regulation topology, which combines the
advantages of hysteretic and voltage mode control. Characteristics of DCS-Control are excellent AC load
regulation and transient response, low-output ripple voltage and a seamless transition between PFM and PWM
mode operation.
DCS-Control includes an AC loop which senses the output voltage (VOS pin) and directly feeds the information
to a fast comparator stage. This comparator sets the switching frequency, which is constant for steady state
operating conditions, and provides immediate response to dynamic load changes. In order to achieve accurate
DC load regulation, a voltage feedback loop is used. The internally compensated regulation network achieves
fast and stable operation with small external components and low ESR capacitors. The DCS-Control topology
supports pulse width modulation (PWM) mode for medium and high load conditions and a power-save mode at
light loads. During PWM mode, it operates in continuous conduction. The switch frequency is up to 1 MHz with a
controlled frequency variation depending on the input voltage. If the load current decreases, the converter
seamless enters power-save mode to maintain high efficiency down to very light loads. In power-save mode the
switching frequency varies linearly with the load current. Because DCS-Control supports both operation modes
within one single building block, the transition from PWM to power-save mode is seamless without effects on the
output voltage. The TPS62125 offers both excellent DC voltage and superior load transient regulation, combined
with very low-output voltage ripple, minimizing interference with RF circuits.
At high load currents the converter operates in quasi fixed frequency PWM mode operation and at light loads in
pulse frequency modulation (PFM) mode to maintain highest efficiency over the full load current range. In PFM
mode, the device generates a single switching pulse to ramp up the inductor current and recharge the output
capacitor, followed by a sleep period where most of the internal circuits are shutdown to achieve a quiescent
current of typically 13 µA. During this time, the load current is supported by the output capacitor. The duration of
the sleep period depends on the load current and the inductor peak current.
7.2 Functional Block Diagram
ON/
SD
VREF
EN
1.2V
VREF_FB
0.808V
Softstart
Softstart
PG Comparator
EN
VREF
PG
VTH_PG
UVLO
Comparator
FB
VIN
EN
Comparator
VUVLO
EN_hys
EN_comp
DC-DC
ON/OFF
Peak Current
Limit Comparator
GND
Limit
High Side
Timer
DCS
Control
VOS
VIN
VOS
Min. On
Control
Logic
VIN
PMOS
Min. OFF
Direct Control
& Compensation
Gate Driver
Anti
Shoot-Through
SW
VREF_FB
FB
Error
amplifier
fixed
VOUT
NMOS
Comparator
GND
Thermal
Shutdown
Zero Current
Comparator
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7.3 Feature Description
7.3.1 Undervoltage Lockout
In addition to the EN comparator, the device includes an under-voltage lockout circuit which prevents the device
from misoperation at low input voltages. Both circuits are fed to an AND gate and prevents the converter from
turning on the high-side MOSFET switch or low-side MOSFET under undefined conditions. The UVLO threshold
is set to 2.9 V typical for rising VIN and 2.8 V typical for falling VIN. The hysteresis between rising and falling
UVLO threshold ensures proper start-up. Fully functional operation is permitted for an input voltage down to the
falling UVLO threshold level. The converter starts operation again once the input voltage trips the rising UVLO
threshold level and the voltage at the EN pin trips VTH_EN_ON.
7.3.2 Enable Comparator (EN / EN_hys)
The EN pin is connected to an on/shutdown detector (ON/SD) and an input of the enable comparator. With a
voltage level of 0.4 V or less at the EN pin, the ON/SD detector turns the device into Shutdown mode and the
quiescent current is reduced to typically 350 nA. In this mode the EN comparator as well the entire internalcontrol circuitry are switched off. A voltage level of typical 900 mV (rising) at the EN pin triggers the on/shutdown
detector and activates the internal reference VREF (typical 1.2 V), the EN comparator and the UVLO comparator.
In applications with slow rising voltage levels at the EN pin, the quiescent current profile before this trip point
needs to be considered, see Figure 3. Once the ON/SD detector has tripped, the quiescent current consumption
of the device is typical 6 µA. The TPS62125 starts regulation once the voltage at the EN pin trips the threshold
VEN_TH ON (typical 1.2 V) and the input voltage is above the UVLO threshold. It enters softstart and ramps up the
output voltage. For proper operation, the EN pin must be terminated and must not be left floating. The quiescent
current consumption of the TPS62125 is typical 13 µA under no load condition (not switching). See Figure 1. The
DC/DC regulator stops operation once the voltage on the EN pin falls below the threshold VEN_TH OFF (typical 1.15
V) or the input voltage falls below UVLO threshold. The enable comparator features a built in hysteresis of typical
50 mV. This hysteresis can be increased with an external resistor connected to pin EN_hys.
7.3.3 Power Good Output and Output Discharge (PG)
The power good output (PG pin) is an open drain output. The circuit is active once the device is enabled. It is
driven by an internal comparator connected to the FB pin voltage and an internal reference. The PG output
provides a high level (open drain high impedance) once the feedback voltage exceeds typical 95% of its nominal
value. The PG output is driven to low level once the FB pin voltage falls below typical 90% of its nominal value
VREF_FB. The PG output goes high (high impedance) with a delay of typically 2 µs. A pull up resistor is needed to
generate a high level. The PG pin can be connected via a pull up resistors to a voltage up to 10 V. This pin can
also be used to discharge the output capacitor. See section Application Information for more details.
The PG output is pulled low if the voltage on the EN pin falls below the threshold VEN_TH
is below the undervoltage lockout threshold UVLO.
OFF
or the input voltage
7.3.4 Thermal Shutdown
As soon as the junction temperature, TJ, exceeds 150°C (typical) the device goes into thermal shutdown. In this
mode, the high-side and low-side MOSFETs are turned-off. The device continues its operation when the junction
temperature falls below the thermal shutdown hysteresis.
7.4 Device Functional Modes
7.4.1 Pulse Width Modulation (PWM) Operation
The TPS62125 operates with pulse width modulation in continuous conduction mode (CCM) with a nominal
switching frequency of about 1 MHz. The frequency variation in PWM mode is controlled and depends on VIN,
VOUT and the inductance. The device operates in PWM mode as long the output current is higher than half the
inductor's ripple current. To maintain high efficiency at light loads, the device enters power-save mode at the
boundary to discontinuous conduction mode (DCM). This happens if the output current becomes smaller than
half the inductor's ripple current.
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Device Functional Modes (continued)
7.4.2 Power-Save Mode
With decreasing load current, the TPS62125 transitions seamlessly from PWM mode to power-save mode once
the inductor current becomes discontinuous. This ensures a high efficiency at light loads. In power-save mode
the converter operates in pulse frequency modulation (PFM) mode and the switching frequency decreases
linearly with the load current. DCS-Control features a small and predictable output voltage ripple in power-save
mode. The transition between PWM mode and power-save mode occurs seamlessly in both directions.
The minimum ON-time TONmin for a single pulse can be estimated by:
TON =
VOUT
´ 1ms
VIN
(1)
Therefore the peak inductor current in PFM mode is approximately:
(VIN - VOUT ) ´ T
ILPFMpeak =
ON
L
where
•
•
•
•
•
TON: High-side MOSFET switch on time [µs]
VIN: Input voltage [V]
VOUT: Output voltage [V]
L : Inductance [µH]
ILPFMpeak : PFM inductor peak current [mA]
(2)
The transition from PFM mode to PWM mode operation and back occurs at a load current of approximately 0.5 x
ILPFMpeak.
The maximum switching frequency can be estimated by:
f SW max »
1
= 1MHz
1ms
(3)
7.4.3 100% Duty Cycle Low Dropout Operation
The device increases the ON-time of the high-side MOSFET switch as the input voltage comes close to the
output voltage in order to keep the output voltage in regulation. This reduces the switching frequency.
With further decreasing input voltage VIN, the high-side MOSFET switch is turned on completely. In this case, the
converter provides a low input-to-output voltage difference. This is particularly useful in applications with a widely
variable supply voltage to achieve longest operation time by taking full advantage of the whole supply voltage
span.
The minimum input voltage to maintain output voltage regulation depends on the load current and output voltage,
and can be calculated as:
VIm in = VOUT min + I OUT ´ ( RDSON max + RL )
where
•
•
•
•
IOUT: Output current
RDS(ON)max: Maximum high-side switch RDS(ON)
RL: DC resistance of the inductor
VOUTmin: Minimum output voltage the load can accept
(4)
7.4.4 Soft-Start
The TPS62125 has an internal soft-start circuit which controls the ramp up of the output voltage and limits the
inrush current during start-up. This limits input voltage drop.
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Device Functional Modes (continued)
The soft-start system generates a monotonic ramp up of the output voltage and reaches an output voltage of 1.8
V typical within 240 µs after the EN pin was pulled high. For higher output voltages, the ramp up time of the
output voltage can be estimated with a ramp up slew rate of about 12 mV/us. TPS62125 is able to start into a
prebiased output capacitor. The converter starts with the applied bias voltage and ramps the output voltage to its
nominal value. In case the output voltage is higher than the nominal value, the device starts switching once the
output has been discharged by an external load or leakage current to its nominal output voltage value.
During start-up the device can provide an output current of half of the high-side MOSFET switch current limit
ILIMF. Large output capacitors and high load currents may exceed the current capability of the device during startup. In this case the start-up ramp of the output voltage will be slower.
7.4.5 Short-Circuit Protection
The TPS62125 integrates a high-side MOSFET switch current limit, ILIMF, to protect the device against a short
circuit. The current in the high-side MOSFET switch is monitored by a current limit comparator and once the
current reaches the limit of ILIMF , the high-side MOSFET switch is turned off and the low-side MOSFET switch is
turned on to ramp down the inductor current. The high-side MOSFET switch is turned on again once the zero
current comparator trips and the inductor current has become zero. In this case, the output current is limited to
half of the high-side MOSFET switch current limit, 0.5 x ILIMF, typ. 300mA.
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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 TPS62125 is a high-efficiency synchronous step-down converter providing a wide output voltage range from
1.2 V to 10 V.
8.2 Typical Application
TPS62125
VIN = 4V to 17V
VIN
SW
R1
1.8M
VOS
EN
CIN
10µF
VOUT = 3.3V
up to 300mA
L 15µH
FB
COUT
10µF
R2
576k
EN_hys
Rpullup
GND
PG
PWR GOOD
Figure 8. TPS62125 3.3-V Output Voltage Configuration
8.2.1 Design Requirements
The device operates over an input voltage range from 3 V to 17 V. The output voltage is adjustable using an
external feedback divider.
8.2.2 Detailed Design Procedure
8.2.2.1 Output Voltage Setting
The output voltage can be calculated by:
æ
R ö
VOUT = VREF _ FB ´ çç1 + 1 ÷÷
è R2 ø
æ
R
VOUT = 0.8V ´ çç1 + 1
è R2
ö
æV
R1 = R2 ´ ç OUT - 1÷
ø
è 0.8V
ö
÷÷
ø
(5)
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Typical Application (continued)
The internal reference voltage for the error amplifier, VREF_FB, is nominal 0.808 V. However for the feedback
resistor divider selection, it is recommended to use the value 0.800 V as the reference. Using this value, the
output voltage sets 1% higher and provides more headroom for load transients as well for line and load
regulation. The current through the feedback resistors R1 and R2 should be higher than 1 µA. In applications
operating over full temperature range or in noisy environments, this current may be increased for robust
operation. However, higher currents through the feedback resistors impact the light load efficiency of the
converter.
Table 1 shows a selection of suggested values for the feedback divider network for most common output
voltages.
Table 1. Suggested Values for Feedback Divider Network
OUTPUT VOLTAGE
1.2 V
1.8 V
3.3 V
5V
6.7 V
8V
R1 [kΩ]
180
300
1800
1100
1475
1800
R2 [kΩ]
360
240
576
210
200
200
8.2.2.2 Enable Threshold and Hysteresis Setting
ON/SD
VREF
1.2V
VIN
VIN
REN1
EN
EN
Comparator
VTH_EN
REN2
EN_hys
REN HYS
GND
Figure 9. Using the Enable Comparator Threshold and Hysteresis for an Input SVS (Supply Voltage
Supervisor)
The enable comparator can be used as an adjustable input supply voltage supervisor (SVS) to start and stop the
DC/DC converter depending on the input voltage level. The input voltage level, VIN_startup, at which the device
starts up is set by the resistors REN1 and REN2 and can be calculated by :
æ
R
V IN _ startup = V EN _ TH _ ON ´ çç1 + EN 1
REN 2
è
ö
æ
R
÷÷ = 1.2V ´ çç1 + EN 1
REN 2
ø
è
ö
÷÷
ø
(6)
The resistor values REN1 and REN2 can be calculated by:
æ V
ö
æV
ö
R E N 1 = R E N 2 ´ ç IN _ startup - 1 ÷ = R E N 2 ´ çç IN _ startup - 1 ÷÷
çV
÷
è 1 . 2V
ø
è E N _ TH _ O N
ø
R EN 2 =
14
R EN 1
ö
æ V IN _ startup
ç
- 1÷
÷
çV
ø
è EN _ TH _ O N
=
(7)
R EN 1
ö
æ V IN _ startup
çç
- 1 ÷÷
ø
è 1 . 2V
(8)
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The input voltage level VIN_stop at which the device will stop operation is set by REN1, REN2 and REN
be calculated by:
æ
R EN 1
V IN _ stop = V EN _ TH _ OFF ´ ç 1 +
ç
R EN 2 + R EN _ hys
è
ö
æ
R EN 1
÷ = 1 . 15V ´ ç 1 +
÷
ç
R EN 2 + R EN _ hys
ø
è
HYS
and can
ö
÷
÷
ø
(9)
The resistor value REN_hys can be calculated according to:
R EN _ hys =
R EN 1
æ V IN _ stop
ö
ç
- 1÷
çV
÷
è EN _ TH _ OFF
ø
- R EN 2 =
R EN 1
ö
æ V IN _ stop
çç
- 1 ÷÷
ø
è 1 .15V
- R EN 2
(10)
The current through the resistors REN1, REN2, and REN HYS should be higher than 1 µA. In applications operating
over the full temperature range and in noisy environments, the resistor values can be reduced to smaller values.
VIN
DC/DC start
VIN_startup
Hysteresis
VIN_stop
DC/DC stop
VOUT
Proper VOUT ramp up
Figure 10. Using the EN Comparator as Input SVS for Proper VOUT Ramp Up
8.2.2.3 Power Good (PG) Pullup and Output Discharge Resistor
The power good open collector output needs an external pull up resistor to indicate a high level. The pull up
resistor can be connected to a voltage level up to 10 V. The output can sink current up to 0.4 mA with specified
output low level of less than 0.3 V. The lowest value for the pull up resistor can be calculated by:
R Pullup min =
VOUT - 0.3V
0.0004 A
(11)
VOUT
TPS62125
COUT
RPullup
RIPG
PG Comparator
VTH_PG
FB
PG
VPG Power Good
max 10V
Figure 11. PG Open Collector Output
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The PG pin can be used to discharge the output capacitor. The PG output has an internal resistance RIPG of
typical 600 Ω and minimum 400 Ω. The maximum sink current into the PG pin is 10 mA. In order to limit the
discharge current to the maximum allowable sink current into the PG pin, the external pull up resistor RPull up can
be calculated to:
RPullup min =
VOUT
I PG _ max
- RIPG _ min =
VOUT
- 400W
0.01A
(12)
In case a negative value is calculated, the external pull up resistor can be removed and the PG pin can be
directly connected to the output.
8.2.2.4 Output Filter Design (Inductor and Output Capacitor)
The external components have to fulfill the needs of the application, but also the stability criteria of the devices
control loop. The TPS62125 is optimized to work within a range of L and C combinations. The LC output filter
inductance and capacitance have to be considered together, creating a double pole, responsible for the corner
frequency of the converter. Table 2 can be used to simplify the output filter component selection.
Table 2. Recommended LC Output Filter Combinations
INDUCTOR VALUE
[µH] (1)
OUTPUT CAPACITOR VALUE [µF] (2)
10 µF
2 x 10 µF
22 µF
47 µF
15
√
√
√
√
22
(3)
√
√
√
15
√ (3)
√
√
√
22
√ (3)
√
√
√
VOUT 1.2 V - 1.8 V
√
VOUT 1.8 V - 3.3 V
VOUT 3.3 V - 5 V
10
√
√
√
15
√ (3)
√ (3)
√
10
√ (3)
√ (3)
√
15
√
√
√
22
√
√
√
22
VOUT 5 V - 10 V
(1)
(2)
(3)
Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by 20% and -30%.
Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by 20% and -50%.
This LC combination is the standard value and recommended for most applications.
More detailed information on further LC combinations can be found in application note SLVA515.
8.2.2.5 Inductor Selection
The inductor value affects its peak-to-peak ripple current, the PWM-to-PFM transition point, the output voltage
ripple and the efficiency. The selected inductor has to be rated for its DC resistance and saturation current. The
inductor ripple current (ΔIL) decreases with higher inductance and increases with higher VIN or VOUT and can be
estimated according to Equation 13.
Equation 14 calculates the maximum inductor current under static load conditions. The saturation current of the
inductor should be rated higher than the maximum inductor current as calculated with Equation 14. This is
recommended because during heavy load transient the inductor current will rise above the calculated value. A
more conservative way is to select the inductor saturation current according to the high-side MOSFET switch
current limit ILIMF.
(VIN - VOUT )
DIL =
´ TON
L
(13)
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ILmax = Ioutmax +
ΔIL
2
where
•
•
•
•
TON: See Equation 1
L: Inductance
ΔIL: Peak to Peak inductor ripple current
ILmax: Maximum Inductor current
(14)
In DC/DC converter applications, the efficiency is essentially affected by the inductor AC resistance (i.e. quality
factor) and by the inductor DCR value. To achieve high-efficiency operation, take care in selecting inductors
featuring a quality factor above 25 at the switching frequency. Increasing the inductor value produces lower RMS
currents, but degrades transient response. For a given physical inductor size, increased inductance usually
results in an inductor with lower saturation current.
The total losses of the coil consist of both the losses in the DC resistance (RDC) and the following frequencydependent components:
• The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
• Additional losses in the conductor from the skin effect (current displacement at high frequencies)
• Magnetic field losses of the neighboring windings (proximity effect)
• Radiation losses
The following inductor series from different suppliers have been used with the TPS62125.
Table 3. List of Inductors
INDUCTANCE
[µH]
DCR [Ω]
DIMENSIONS
[mm3]
INDUCTOR
TYPE
SUPPLIER
10 / 15
0.33 max / 0.44 max.
3.3 x 3.3 x 1.4
LPS3314
Coilcraft
22
0.36 max.
3.9 x 3.9 x 1.8
LPS4018
Coilcraft
15
0.33 max.
3.0 x 2.5 x 1.5
VLF302515
TDK
10/15
0.44 max / 0.7 max.
3.0 x 3.0 x 1.5
LPS3015
Coilcraft
10
0.38 typ.
3.2 × 2.5 × 1.7
LQH32PN
Murata
8.2.2.6 Output Capacitor Selection
Ceramic capacitors with low ESR values provide the lowest output voltage ripple and are recommended. The
output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from their
wide variation in capacitance over temperature, become resistive at high frequencies.
At light load currents the converter operates in power-save mode and the output voltage ripple is dependent on
the output capacitor value and the PFM peak inductor current. Higher output capacitor values minimize the
voltage ripple in PFM Mode and tighten DC output accuracy in PFM mode. In order to achieve specified
regulation performance and low-output voltage ripple, the DC-bias characteristic of ceramic capacitors must be
considered. The effective capacitance of ceramic capacitors drops with increasing DC-bias voltage. Due to this
effect, it is recommended for output voltages above 3.3 V to use at least 1 x 22-µF or 2 x 10-µF ceramic
capacitors on the output.
8.2.2.7 Input Capacitor Selection
Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is
required for best input voltage filtering and minimizing the interference with other circuits caused by high input
voltage spikes. For most applications, a 10-µF ceramic capacitor is recommended. The voltage rating and DC
bias characteristic of ceramic capacitors need to be considered. The input capacitor can be increased without
any limit for better input voltage filtering.
For applications powered from high impedance sources, a tantalum polymer capacitor should be used to buffer
the input voltage for the TPS62125. Tantalum polymer capacitors provide a constant capacitance vs. DC bias
characteristic compared to ceramic capacitors. In this case, a 10-µF ceramic capacitor should be used in parallel
to the tantalum polymer capacitor to provide low ESR.
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Take care when using only small ceramic input capacitors. When a ceramic capacitor is used at the input and the
power is being supplied through long wires, such as from a wall adapter, a load step at the output or VIN step on
the input can induce large ringing at the VIN pin. This ringing can couple to the output and be mistaken as loop
instability or could even damage the part by exceeding the maximum ratings. In case the power is supplied via a
connector e.g. from a wall adapter, a hot-plug event can cause voltage overshoots on the VIN pin exceeding the
absolute maximum ratings and can damage the device, too. In this case a tantalum polymer capacitor or
overvoltage protection circuit reduces the voltage overshoot, see Figure 45.
Table 4 shows a list of input/output capacitors.
Table 4. List of Capacitors
CAPACITANCE [µF]
SIZE
CAPACITOR TYPE
USAGE
SUPPLIER
10
0805
GRM21B 25V X5R
CIN /COUT
Murata
10
0805
GRM21B 16V X5R
COUT
Murata
22
1206
GRM31CR61 16V X5R
COUT
Murata
22
B2 (3.5x2.8x1.9)
20TQC22MYFB
CIN / input
protection
Sanyo
.
8.2.3 Application Curves
95
95
90
90
85
85
80
80
VIN = 3V
VIN = 5V
VIN = 7.5V
VIN = 9V
VIN = 12V
VIN = 15V
75
70
65
60
0.1
1
10
Output Current IOUT (mA)
100
100mA
250mA
1.0mA
75
VOUT = 1.8V
L = 15mH LPS3314
COUT = 10mF
70
0.25mA
65
60
VOUT = 1.8V
L = 15mH LPS3314
COUT = 10mF
55
50
0.01
Efficiency (%)
Efficiency (%)
10mA
0.1mA
55
50
1000
Figure 12. Efficiency vs. Output Current VOUT = 1.8 V
3
4
5
6
7
8 9 10 11 12 13 14 15 16 17
Input Voltage VIN (V)
Figure 13. Efficiency vs. Input Voltage, VOUT = 1.8 V
100
95
95
90
10mA
90
85
80
VIN = 4.0V
VIN = 5V
VIN = 7.5V
VIN = 9V
VIN = 12V
VIN = 15V
75
70
65
55
0.1
1
10
Output Current (mA)
100
70
0.25mA
VOUT = 3.3V
L = 15mH VLF302515
COUT = 10mF
60
0.1mA
55
1000
50
4
5
6
7
8
9
10 11
12 13 14 15 16 17
Input Voltage VIN(V)
Figure 14. Efficiency vs. Output current, VOUT = 3.3 V
18
1.0mA
75
65
VOUT = 3.3V
L = 15mH VLF302515
COUT = 10mF
60
50
0.01
250mA
80
Efficiency (%)
Efficiency (%)
85
100mA
Figure 15. Efficiency vs. Input voltage, VOUT = 3.3 V
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100
100
95
95
90
90
VIN = 6.0V
VIN = 7.5V
VIN = 9.0V
VIN = 12V
VIN = 15V
80
75
Efficiency (%)
Efficiency (%)
10mA
250mA
85
85
70
70
65
60
55
55
1
10
100
Output Current IOUT (mA)
0.25mA
75
60
0.1
1.0mA
80
VOUT = 5V
L = 10mH LPS3314
COUT = 2x10mF
65
50
0.01
100mA
50
1000
Figure 16. Efficiency vs. Output Current, VOUT = 5 V
VOUT = 5V
L = 10mH LPS3314
COUT = 2x10mF
6
7
8
9
10 11 12 13 14
Input Voltage VIN (V)
100
95
95
90
90
10mA
75
70
VOUT = 6.7V
L = 10mH LPS3314
COUT = 2x10mF
65
50
1000
Figure 18. Efficiency vs. Output current, VOUT = 6.8 V
100
95
95
90
90
7
8
9
10
0.1mA
11
12
13
14
Input Voltage VIN (V)
15
100mA
10mA
Efficiency (%)
VIN = 9.0V
VIN = 12V
VIN = 15V
80
75
VOUT = 8V
L = 10mH LPS3314
COUT = 10mF+22mF
70
65
1.0mA
0.25mA
75
70
VOUT = 8V
L = 10mH LPS3314
COUT = 10mF + 22mF
65
60
55
55
1
10
100
Output Current IOUT (mA)
50
1000
Figure 20. Efficiency vs. Output Current, VOUT = 8 V
17
80
60
0.1
16
250mA
85
85
Efficiency (%)
VOUT = 6.7V
L = 10mH LPS3314
COUT = 2x10mF
Figure 19. Efficiency vs. Input Voltage, VOUT = 6.8 V
100
50
0.01
0.25mA
65
55
100
250mA
70
55
1
10
Output Currernt IOUT (mA)
17
1.0mA
75
60
0.1
16
80
60
50
0.01
100mA
85
Efficiency (%)
Efficiency (%)
85
VIN = 7.5V
VIN = 9V
VIN = 12V
VIN = 15V
15
Figure 17. Efficiency vs. Input Voltage, VOUT = 5 V
100
80
0.1mA
9
10
11
12
13
14
Input Voltage VIN (V)
0.1mA
15
16
17
Figure 21. Efficiency vs. Input Voltage, VOUT = 8 V
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100
100
95
95
90
90
85
85
10mA
100mA
250mA
80
Efficiency (%)
Efficiency (%)
1.0mA
VIN = 12V
VIN = 15V
75
VOUT = 10V
L = 10mH LPS3314
COUT = 10mF + 22mF
70
65
60
55
55
1
10
100
Output Currernt IOUT (mA)
50
1000
Figure 22. Efficiency vs. Output Current, VOUT = 10 V
VOUT 3.3V
L = 15mH,
COUT = 10mF
13
14
15
Input Voltage VIN (V)
16
17
3.35
3.333
VIN = 5V, TA= 25°C
VIN = 7.5V, TA = 25°C
VIN = 12V, TA = 25°C
VIN = 5V, TA = 85°C
VIN = 7.5V, TA = 85°
VIN = 12V, TA = 85°
3.300
3.267
3.234
0.01
0.1
1
10
Output Current [mA]
3.3
IOUT = 1mA
IOUT = 25mA
IOUT = 100mA
IOUT = 150mA
3.25
100
3.2
1000
Figure 24. Output Voltage vs. Output Current, VOUT = 3.3 V
5
6
7
8
9
10 11 12 13
Input Voltage (V)
14
15
16
17
Figure 25. Output Voltage vs. Input Voltage, VOUT = 3.3 V
5.15
5.20
VIN = 7.5V, TA = 25°C
VIN = 12V, TA = 25°C
VIN = 7.5V, TA = -40°C
VIN = 12V, TA = -40°C
VIN = 7.5V, TA = 85°
VIN = 12V, TA = 85°
5.05
5.05
5
5.00
4.95
4.95
4.9
0.1
1
10
Output Current [mA]
100
VOUT 5.0V
L = 10mH,
COUT = 2x10mF
5.1
Output Voltage (V)
VOUT 5.0V
L = 10mH,
COUT = 2x10mF
5.10
4.90
0.01
12
VOUT 3.3V
L = 15mH,
COUT = 10mF
VIN = 5V, TA = -40°C
VIN = 7.5V, TA = -40°C
VIN = 12V, TA = -40°C
3.366
5.15
11
3.4
Output Voltage (V)
Output Voltage [V]
3.399
0.1mA
VOUT = 10V
L = 10mH LPS3314
COUT = 10mF+22mF
Figure 23. Efficiency vs. Input Voltage, VOUT = 10 V
3.432
Output Voltage [V]
70
60
0.1
0.25mA
75
65
50
0.01
1000
4.85
IOUT = 1mA
IOUT = 25mA
IOUT = 100mA
IOUT = 250mA
7
8
9
10
11
12
13
14
15
16
17
Input Voltage (V)
Figure 26. Output Voltage vs. Output current, VOUT = 5 V
20
80
Figure 27. Output Voltage vs. Input Voltage, VOUT = 5 V
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6.968
6.9
VOUT 6.7V
L = 10mH,
COUT = 2x10mF
6.85
6.901
VIN = 12V, TA = 25°C
VIN = 9V, TA = -40°C
Output Voltage [V]
6.8
VIN = 9V, TA = 25°C
Output Voltage [V]
VIN = 12V, TA = -40°C
6.834
6.767
VIN = 9V, TA = 85°
6.700
6.75
6.7
6.65
VIN = 12V, TA = 85°
6.633
6.55
6.5
6.566
0.01
0.1
IOUT = 1mA
IOUT = 25mA
IOUT = 100mA
IOUT = 250mA
6.6
VOUT 6.7V
L = 10mH,
COUT = 2x10mF
1
10
Output Current [mA]
100
1000
Figure 28. Output Voltage vs. Output Current, VOUT = 6.7 V
8
11
12
13
14
Input Voltage [V]
15
16
17
8.24
VOUT 8.0V
L = 10mH,
COUT = 10mF + 22mF
8.24
VOUT 8.0V
L = 10mH,
COUT = 10mF + 22mF
8.16
VIN = 15V, TA = -40°C
8.16
VIN = 15V, TA = 25°C
8.08
Output Voltage [V]
Output Voltage [V]
10
Figure 29. Output voltage vs. Input voltage, VOUT = 6.7 V
8.32
VIN = 12V, TA = -40°C
8.08
8
7.92
8.00
VIN = 12V, TA = 25°C
7.84
0.01
7.84
7.76
0.1
IOUT = 1mA
IOUT = 25mA
IOUT = 100mA
IOUT = 250mA
VIN = 12V, TA = 85°
VIN = 15V, TA = 85°
7.92
1
10
Output Current [mA]
100
1000
9
10
11
12
13
14
15
16
17
Input Voltage [V]
Figure 30. Output Voltage vs. Output Current, VOUT = 8 V
50
Figure 31. Output Voltage vs. Input Voltage, VOUT = 8 V
1000
40
VIN = 12V
900
VOUT = 3.3V
L = 15mH
COUT = 10mF
Switch Frequency fSW( kHz)
Output Ripple Voltage (mVpp)
9
30
20
VIN = 15V
800
700
VIN = 7.5V
600
500
VIN = 5V
400
300
VIN = 5.0V
VIN = 7.5V
VIN = 12V
VIN = 15V
10
0
0
50
100
150
200
Output Current (mA)
250
VOUT = 3.3V
L = 15mH
COUT = 10mF
200
100
0
300
Figure 32. Output Ripple Voltage vs. Output Current,
VOUT = 3.3 V
0
50
100
150
200
Output Current (mA)
250
300
Figure 33. Switch Frequency vs. Output Current,
VOUT = 3.3 V
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1200
1200
1100
VIN = 12V
VIN = 7.5V
900
800
700
600
500
900
800
VIN = 10V
700
600
500
400
400
VOUT = 5.0V
L = 10mH
COUT = 2x10mF
300
200
300
VOUT = 8.0V
L = 10mH
COUT = 10mF + 22mF
200
100
100
0
0
50
100
150
200
Output Current (mA)
250
VOUT = 3.3 V
3.3V offset, 50mV/Div
ILoad = 1mA
0
300
Figure 34. Switch Frequency vs. Output Current, VOUT 5 V
VIN = 12V
L = 15 mH
COUT = 10 mF
SW pin 10V/Div
0
50
100
150
200
Output Current (mA)
250
300
Figure 35. Switch Frequency vs. Output Current, VOUT = 8
V
VOUT = 3.3 V
3.3V offset, 50mV/Div
ILoad = 100mA
VIN = 12V
L = 15 mH
COUT = 10 mF
SW pin 10V/Div
Inductor current 200mA/Div
Inductor current 200mA/Div
Figure 36. Power-Save Mode VOUT= 3.3 V, IOUT = 1 mA
VOUT = 3.3 V
3.3V offset, 50mV/Div
VIN = 12V
L = 15 mH
COUT = 10 mF
SW pin 10V/Div
Figure 37. PWM Mode VOUT= 3.3 V, IOUT = 100 mA
VOUT = 3.3 V
3.3V offset, 50mV/Div
VIN = 12V
L = 15 mH
COUT = 10 mF
SW pin 10V/Div
IOUT
5mA to 200mA
200mA/Div
Inductor current
200mA/Div
Inductor current
200mA/Div
Figure 38. Load Transient 5 mA to 200 mA, VOUT = 3.3 V
22
VIN = 15V
VIN = 12V
1000
Switch Frequency FSW ( kHz)
1000
Frequency ( kHz)
1100
VIN = 15V
IOUT
AC 10kHz
5mA to 200mA
200mA/Div
Figure 39. AC Load Regulation, VOUT = 3.3 V
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VIN = 12V
L = 10 mH
COUT = 2x 10 mF
VOUT = 5.0 V
5V offset, 50mV/Div
Inductor current 200mA/Div
Inductor current 200mA/Div
ILoad = 1mA to 50mA
50mA / Div
ILoad = 10mA to 200mA
200mA / Div
Figure 40. Load Transient 1 mA to 50 mA, VOUT = 5 V
VOUT = 5.0 V
5V offset, 50mV/Div
VIN = 12V
L = 10 mH
COUT = 2x 10 mF
VOUT = 5.0 V
5V offset, 50mV/Div
Figure 41. Load Transient 10 mA to 200 mA, VOUT = 5 V
VIN = 9V to 12V
IOUT = 100mA
L = 15 mH
COUT = 10 mF
VIN = 12V
L = 10 mH
COUT = 2x 10 mF
VOUT
= 3.3 V, 50mV/Div
Inductor current 200mA/Div
ILoad = AC 5kHz 1mA to 250mA
200mA / Div
Figure 43. Line Transient Response VIN = 9 V to 12 V
Figure 42. AC Load Regulation VOUT = 5 V
VIN overshoot 25V
IIN
VIN = 12V, Hotplug
CIN = 10mF ceramic capacitor
Current into
input capacitor 20A/div
VIN overshoot reduction
to 15V
Current into
input capacitors 20A/div
IIN
Figure 44. VIN Hotplug Overshoot
VIN = 12V, Hotplug
CIN = 10mF
additional 22mF
tantalum-polymer input capacitor
type Poscap 20TQC22MYFB
Figure 45. VIN Hotplug Overshoot Reduction With Poscap
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VOUT = 5.0 V
2V/Div
www.ti.com
VIN = 12V
CIN = 10uF ceramic
+ 22uF Poscap
VOUT
Startup
L = 10 mH
COUT = 2x 10 mF
IIN
200mA/Div
VIN : ramped up/down
0V to 12V, 175mV/ms
2.5V/Div
REN1 = 820kW
REN2 = 110kW
REN2 = 82kW
VOUT = 5.0 V
L = 10 mH
COUT = 2x10 mF
Load = 100W
VIN_Start = 10V
VIN_Stop = 6V
Current into CIN
VOUT
2.5V/Div
IL
1A/Div
PG
5V/Div
Short
IOUT
1A/Div
IOUT = 10mA
Short
IIN
200mA/Div
Figure 47. Input Supply Voltage Supervisor (SVS),
VOUT = 5 V
Figure 46. Short Circuit and Overcurrent Protection
VIN : ramped up/down
0V to 12V, 175mV/ms
2.5V/Div
EN = VIN
UVLO
VOUT = 5.0 V
L = 10 mH
COUT = 2x10 mF
Load = 100W
VIN tracks VOUT
VIN: 0.5mA current source
2.5V/Div
REN1 = 680kW
REN2 = 110kW
REN2 = 120kW
VIN_startup = 6.82V
VIN_stop = 4.55V
CIN = 10mF ceramic + 22mF Poscap
VOUT = 3.3 V
L = 15 mH, COUT = 10 mF
UVLO
7ms/20mA Pulse Load
VOUT
2.5V/Div
VOUT
2.0V/Div
PG
5V/Div
IOUT
20mA/Div
Startup in 20mA Load
0.5mA Source Current
IIN
200mA/Div
IIN: 0.5mA/Div
Figure 48. Operation With EN = VIN, VIN Tracks VOUT
VIN = 12V
VOUT = 1.8 V
L = 15 mH
COUT = 10 mF
Load = 180W
Figure 49. 0.5 mA Current Source, 20 mA Pulse Load
VIN = 12V
VOUT = 3.3 V
L = 15 mH
COUT = 10 mF
Load = 330W
Figure 50. Start-Up 1.8 V VOUT
24
Figure 51. Start-Up 3.3 V VOUT
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VIN = 12V
VOUT = 8.0 V
L = 10 mH
COUT = 2x10 mF
Load = 800W
VIN = 12V
VOUT = 5.0 V
L = 10 mH
COUT = 2x10 mF
Load = 500W
Figure 52. Start-Up 5 V VOUT
Figure 53. Start-Up 8 V VOUT
VIN = 12V
VOUT = 3.3 V
COUT = 10uF
L = 15mH
RLoad = 100 W
RPullup PG = 100kW to VOUT
VIN
1V/Div
VIN_stop = 4.55V
REN1 = 680kW
REN2 = 110kW
REN_hys = 120kW
VIN = 12V to 0V
VOUT = 3.3 V
COUT = 10uF
L = 15mH
IOUT = 0mA
RPullup PG = 0W to VOUT
1V/Div
VOUT
1V/Div
2V/Div
1V/Div
Figure 54. VOUT Ramp Up/Down With EN On/Off
VIN
2V/Div
VIN_stop = 4.55V
REN1 = 680kW
REN2 = 110kW
REN_hys = 120kW
Figure 55. Output Discharge Using PG Pin, Triggered by
EN Comparator
VIN = 12V to 0V
VOUT = 3.3 V
COUT = 10uF
L = 15mH
IOUT = 0mA
RPullup PG = 100kW to VOUT
VOUT
1V/Div
PG
1V/Div
Figure 56. VOUT Ramp Down With Falling VIN, See Schematic Figure 59
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8.3 System Examples
8.3.1 TPS62125 5-V Output Voltage Configuration
TPS62125
VIN = 6V to 17V
VOUT = 5V
up to 300mA
L 10µH
SW
VIN
R1
1.1M
VOS
EN
CIN
10µF
FB
R2
210k
EN_hys
COUT
2 x 10µF
or 1 x 22µF
Rpullup
GND
PG
PWR GOOD
Figure 57. TPS62125 5-V Output Voltage Configuration
8.3.2 TPS62125 5-V VOUT
VIN_Start = 10V
VIN_Stop = 6V
TPS62125
SW
VIN
REN1
820k
CIN
10µF
VOUT = 5V
up to 300mA
L 10µH
R1
1.1M
VOS
R2
REN2
110k
FB
EN
R2
210k
COUT
2 x 10µF
or 1 x 22µF
EN_hys
REN_hys
82k
Rpullup
GND
PG
PWR GOOD
Figure 58. TPS62125 5-V VOUT, Start-up Voltage VIN_Start = 10 V, Stop Voltage VIN_Stop = 6 V, See Figure 47
8.3.3 TPS62125 Operation From a Storage Capacitor Charged From a 0.5 mA Current Source
VIN_Start = 6.82V
VIN_Stop = 4.55V
TPS62125
VIN
Current
Source
0.5mA
10V max
REN1
610k
CIN
22µF
Poscap
CIN
10µF
REN2
110k
SW
R1
1.8M
VOS
R2
EN
VOUT = 3.3V
up to 300mA
L 15µH
FB
COUT
10µF
R2
576k
EN_hys
REN_hys
120k
Rpullup
100k
GND
PG
PWR Good
Figure 59. TPS62125 Operation From a Storage Capacitor Charged From a 0.5 mA Current Source,
VOUT = 3.3 V, See Figure 49
26
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System Examples (continued)
8.3.4 5 V to –5 V Inverter Configuration
CIN
10µF
VIN = 5V
TPS62125
VOS
EN
GND
R1
1.1M
FB
Cbypass
10µF
R2
210k
EN_hys
GND
L 10µH
SW
VIN
PG
COUT
2 x 10µF
or 1 x 22µF
VOUT = - 5V
up to 150mA
Figure 60. 5 V to –5 V Inverter Configuration, See SLVA514
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9 Power Supply Recommendations
The TPS62125 has no special requirements for its input power supply. The input power supply's output current
needs to be rated according to the supply voltage, output voltage, and output current of the TPS62125.
10 Layout
10.1 Layout Guidelines
As for all switching power supplies, the layout is an important step in the design. Proper function of the device
demands careful attention to PCB layout. Take care in the board layout to get the specified performance. If the
layout is not carefully done, the regulator could show frequency variations, poor line and/or load regulation,
stability issues as well as EMI problems. It is critical to provide a low-inductance, low-impedance ground path.
Therefore, use wide and short traces for the paths conducting AC current of the DC/DC converter. The area of
the AC current loop (input capacitor – TPS62125 – inductor – output capacitor) should be routed as small as
possible to avoid magnetic field radiation. Therefore the input capacitor should be placed as close as possible to
the IC pins as well as the inductor and output capacitor. Use a common power GND node and a different node
for the signal GND to minimize the effects of ground noise. Keep the common path to the GND pin, which returns
both the small signal components and the high current of the output capacitors as short as possible to avoid
ground noise. A well proven practice is to merge small signal GND and power GND path at the exposed thermal
pad. The FB divider network and the FB line should be routed away from the inductor and the SW node to avoid
noise coupling. The VOS line should be connected as short as possible to the output, ideally to the VOUT terminal
of the inductor. Keep the area of the loop VOS node – inductor – SW node small. The exposed thermal pad must
be soldered to the circuit board for mechanical reliability and to achieve appropriate power dissipation.
10.2 Layout Example
COUT
L
PG
GND
Approximate circuit area
2
2
= 51mm (0.079in )
VOUT
CIN
VIN
REN1
REN2
U1
GND
R1
R2
REN_hys
Figure 61. EVM Board Layout
28
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
11.3 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.
11.4 Trademarks
DCS-Control, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 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.
11.6 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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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)
TPS62125DSGR
ACTIVE
WSON
DSG
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
SAQ
TPS62125DSGT
ACTIVE
WSON
DSG
8
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
SAQ
(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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