TPS65251-1, TPS65251-2, TPS65251-3
SLVSC70B – JANUARY 2015 – REVISED JANUARY 2022
TPS65251-x 4.5-V to 18-V Input, High Current, Synchronous Step Down Three Buck
Switchers With Integrated FET
divider to any value between 0.8 V and close to
the input supply. Each converter features an enable
pin that allows a delayed start-up for sequencing
purposes, soft-start pin that allows adjustable softstart time by choosing the soft-start capacitor, and a
current limit (RLIMx) pin that enables the designer to
adjust current limit by selecting an external resistor
and optimize the choice of inductor. The current mode
control allows a simple RC compensation.
1 Features
•
•
•
•
•
•
•
•
•
•
•
•
•
Wide input supply voltage range (4.5 to 18 V)
Output range: 0.8 V to VIN – 1 V
Continuous loading: 3 A (buck 1),
2 A (buck 2 and 3)
Maximum current: 3.5 A (buck 1),
2.5 A (buck 2 and 3)
Adjustable switching frequency
300 kHz to 2.2 MHz set by external resistor
Dedicated enable for each buck
External synchronization pin for oscillator
Adjustable current limit set by external resistor
Soft-start pins
Current-mode control with simple compensation
circuit
Power good
Automatic PFM/PWM operation
VQFN package, 40-pin 6-mm × 6-mm RHA
The switching frequency of the converters can either
be set with an external resistor connected to ROSC
pin or can be synchronized to an external clock
connected to the SYNC pin if needed. The switching
regulators are designed to operate from 300 kHz
to 2.2 MHz. 180° out-of-phase operation between
Buck 1 and Buck 2, 3 (Buck 2 and 3 run in phase)
minimizes the input filter requirements.
TPS65251-x features a supervisor circuit that
monitors each converter output. The PGOOD pin is
asserted when sequencing is done, all PG signals are
reported and a selectable end of reset time lapses.
The polarity of the PGOOD signal is active high.
2 Applications
•
•
•
•
•
•
Set top boxes
Blu-ray™ DVD
DVR
DTV
Car audio/video
Security camera
All converters feature an automatic low-power pulse
PFM skipping mode, which improves efficiency during
light loads and standby operation, while ensuring a
very-low output ripple, allowing for a value of less than
2% at low output voltages.
3 Description
The TPS65251-x features three synchronous wideinput range, high-efficiency buck converters. The
converters are designed to simplify its application
while giving the designer the option to optimize their
usage according to the target application.
Device Information
TPS65251-1
The converters can operate in 5-, 9-, 12- or 15-V
systems and have integrated power transistors. The
output voltage can be set externally using a resistor
(1)
PART NUMBER
TPS65251-2
PACKAGE(1)
VQFN (40)
BODY SIZE (NOM)
6.00 mm × 6.00 mm
TPS65251-3
For all available packages, see the orderable addendum at
the end of the data sheet.
CMP2
SS2
RLIM2
GND
LOW_P
FB2
V3V
V7V
PGOOD
AGND
FB2
GND
FB2
EN2
BST2
VIN
VIN
VIN
VIN
SS1
RLIM1
CMP1
EN1
V1
VIN1
FB1
FB1
FB3
FB3
LX1
VIN1
BST1
SYNC
ROSC
FB1
VIN3
BST3
EN3
V2
LX2
LX2
LX1
TPS65251-X
GND
LX3
LX3
RLIM3
VIN3
VIN2
SS3
CMP3
FB3
V3
VIN2
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.
TPS65251-1, TPS65251-2, TPS65251-3
www.ti.com
SLVSC70B – JANUARY 2015 – REVISED JANUARY 2022
Table of Contents
1 Features............................................................................1
2 Applications..................................................................... 1
3 Description.......................................................................1
4 Revision History.............................................................. 2
5 Pin Configuration and Functions...................................3
6 Specifications.................................................................. 5
6.1 Absolute Maximum Ratings........................................ 5
6.2 ESD Ratings............................................................... 5
6.3 Recommended Operating Conditions.........................5
6.4 Thermal Information....................................................5
6.5 Electrical Characteristics.............................................6
6.6 Typical Characteristics for Buck 1...............................8
6.7 Typical Characteristics for Buck 2...............................9
6.8 Typical Characteristics for Buck 3.............................10
7 Detailed Description...................................................... 11
7.1 Overview................................................................... 11
7.2 Functional Block Diagram......................................... 11
7.3 Feature Description...................................................12
7.4 Device Functional Modes..........................................15
8 Application and Implementation.................................. 16
8.1 Application Information............................................. 16
8.2 Typical Application.................................................... 16
9 Power Supply Recommendations................................29
10 Layout...........................................................................30
10.1 Layout Guidelines................................................... 30
10.2 Layout Example...................................................... 31
11 Device and Documentation Support..........................32
11.1 Receiving Notification of Documentation Updates.. 32
11.2 Support Resources................................................. 32
11.3 Trademarks............................................................. 32
11.4 Electrostatic Discharge Caution.............................. 32
11.5 Glossary.................................................................. 32
12 Mechanical, Packaging, and Orderable
Information.................................................................... 32
4 Revision History
Changes from Revision A (January 2015) to Revision B (January 2022)
Page
• Updated the numbering format for tables, figures, and cross-references throughout the document. ................1
• Change VIN1, VIN2, VIN3, LX1, LX2, and LX3 maximum rating voltage from 18 V to 20 V..............................5
• Change LX1, LX2, and LX3 minimum rating voltage from –1 V to –3 V.............................................................5
Changes from Revision * (January 2015) to Revision A (January 2015)
Page
• Updated device status to production data ......................................................................................................... 1
2
Submit Document Feedback
Copyright © 2022 Texas Instruments Incorporated
Product Folder Links: TPS65251-1 TPS65251-2 TPS65251-3
TPS65251-1, TPS65251-2, TPS65251-3
www.ti.com
SLVSC70B – JANUARY 2015 – REVISED JANUARY 2022
5 Pin Configuration and Functions
GND
LOW_P
26
25
RLIM2
PGOOD
27
SS2
V7V
28
FB2
V3V
29
COMP2
AGND
30
24
23
22
21
GND
31
20
VIN
32
19
BST2
VIN
33
18
VIN2
VIN
34
17
LX2
GND
35
16
LX2
LX3
36
15
LX1
LX3
37
14
LX1
VIN3
38
13
VIN1
BST3
39
12
BST1
EN3
40
11
EN1
FB3
7
8
9
10
RLIM1
CMP3
6
SS1
SS3
5
CMP1
4
FB1
3
SYNC
2
ROSC
1
RLIM3
QFN RHA40
(power pad connected to ground)
EN2
Table 5-1. Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
RLIM3
1
I
Current limit setting for Buck 3. Fit a resistor from this pin to ground to set the peak current limit on the output
inductor.
SS3
2
I
Soft-start pin for Buck 3. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
COMP3
3
O
Compensation for Buck 3. Fit a series RC circuit to this pin to complete the compensation circuit of this
converter.
FB3
4
I
Feedback input for Buck 3. Connect a divider set to 0.8 V from the output of the converter to ground.
SYNC
5
I
Synchronous clock input. If there is a sync clock in the system, connect to the pin. When not used, connect to
GND.
ROSC
6
I
Oscillator set. This resistor sets the frequency of the internal autonomous clock. If external synchronization is
used, the resistor should be fitted and set to about 70% of external clock frequency.
FB1
7
I
Feedback pin for Buck 1. Connect a divider set to 0.8 V from the output of the converter to ground.
COMP1
8
O
Compensation pin for Buck 1. Fit a series RC circuit to this pin to complete the compensation circuit of this
converter.
SS1
9
I
Soft-start pin for Buck 1. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
RLIM1
10
I
Current limit setting pin for Buck 1. Fit a resistor from this pin to ground to set the peak current limit on the output
inductor.
EN1
11
I
Enable pin for Buck 1. A low-level signal on this pin disables it. If pin is left open, a weak internal pull-up to V3V
allows for automatic enable. For a delayed start-up, add a small ceramic capacitor from this pin to ground.
BST1
12
I
Bootstrap capacitor for Buck 1. Fit a 47-nF ceramic capacitor from this pin to the switching node.
VIN1
13
I
Input supply for Buck 1. Fit a 10-µF ceramic capacitor close to this pin.
O
Switching node for Buck 1
O
Switching node for Buck 2
LX1
LX2
14
15
16
17
VIN2
18
I
Input supply for Buck 2. Fit a 10-µF ceramic capacitor close to this pin.
BST2
19
I
Bootstrap capacitor for Buck 2. Fit a 47-nF ceramic capacitor from this pin to the switching node.
Copyright © 2022 Texas Instruments Incorporated
Product Folder Links: TPS65251-1 TPS65251-2 TPS65251-3
Submit Document Feedback
3
TPS65251-1, TPS65251-2, TPS65251-3
www.ti.com
SLVSC70B – JANUARY 2015 – REVISED JANUARY 2022
Table 5-1. Pin Functions (continued)
PIN
NAME
NO.
I/O
DESCRIPTION
EN2
20
I
Enable pin for Buck 2. A low-level signal on this pin disables it. If pin is left open, a weak internal pull-up to V3V
allows for automatic enable. For a delayed start-up, add a small ceramic capacitor from this pin to ground.
RLIM2
21
I
Current limit setting for Buck 2. Fit a resistor from this pin to ground to set the peak current limit on the output
inductor.
SS2
22
I
Soft-start pin for Buck 2. Fit a small ceramic capacitor to this pin to set the converter soft-start time.
COMP2
23
O
Compensation pin for Buck 2. Fit a series RC circuit to this pin to complete the compensation circuit of this
converter
FB2
24
I
Feedback input for Buck 2. Connect a divider set to 0.8 V from the output of the converter to ground.
LOW_P
25
I
Low-power operation mode (active-high) input for TPS65251
GND
26
PGOOD
27
O
Power good. Open-drain output asserted after all converters are sequenced and within regulation. Polarity is
factory selectable (active-high default).
V7V
28
O
Internal supply. Connect a 10-μF ceramic capacitor from this pin to ground.
V3V
29
O
Internal supply. Connect a 3.3- to 10-μF ceramic capacitor from this pin to ground.
AGND
30
Analog ground. Connect all GND pins and the power pad together.
GND
31
Ground pin
Ground pin
32
VIN
33
I
Input supply
34
GND
LX3
4
35
36
37
Ground pin
O
Switching node for Buck 3
VIN3
38
Input supply for Buck 3. Fit a 10-µF ceramic capacitor close to this pin.
BST3
39
I
Bootstrap capacitor for Buck 3. Fit a 47-nF ceramic capacitor from this pin to the switching node.
EN3
40
I
Enable pin for Buck 3. A low-level signal on this pin disables it. If pin is left open, a weak internal pull-up to V3V
allows for automatic enable. For a delayed start-up, add a small ceramic capacitor from this pin to ground.
PAD
—
—
Power pad. Connect to ground.
Submit Document Feedback
Copyright © 2022 Texas Instruments Incorporated
Product Folder Links: TPS65251-1 TPS65251-2 TPS65251-3
TPS65251-1, TPS65251-2, TPS65251-3
www.ti.com
SLVSC70B – JANUARY 2015 – REVISED JANUARY 2022
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)
MIN
MAX
UNIT
–0.3
20
V
–3
23
V
BST1, BST2, BST3, referenced to Lx pin
–0.3
7
V
V7V
–0.3
7
V
V3V, RLIM1, RLIM2, RLIM3, EN1, EN2, EN3, SS1, SS2,SS3, FB1, FB2, FB3, PGOOD, SYNC,
ROSC, RST_IN, LOW_P, COMP1, COMP2, COMP3
–0.3
3.6
V
AGND, GND
–0.3
0.3
V
TJ
Operating virtual junction temperature
–40
125
°C
Tstg
Storage temperature
–55
150
°C
VIN1,VIN2, VIN3, LX1, LX2, LX3
LX1, LX2, LX3 (maximum withstand voltage transient