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LM25088, LM25088-Q1
SNVS609J – DECEMBER 2008 – REVISED JANUARY 2015
LM25088, LM25088-Q1 Wide Input Range Non-Synchronous Buck Controller
1 Features
1
3 Description
The LM25088 high voltage non-synchronous buck
controller features all the necessary functions to
implement an efficient high voltage buck converter
using a minimum number of external components.
The LM25088 can be configured to operate over an
ultra-wide input voltage range of 4.5 V to 42 V. This
easy to use controller includes a level shifted gate
driver capable of controlling an external N-channel
buck switch. The control method is based upon peak
current mode control utilizing an emulated current
ramp. The use of an emulated control ramp reduces
noise sensitivity of the pulse-width modulation circuit,
allowing reliable control of very small duty cycles
necessary in high input voltage/low output voltage
applications. The LM25088 switching frequency is
programmable from 50 kHz to 1 MHz.
The LM25088 is available in two versions: The
LM25088-1 provides a +/-5% frequency dithering
function to reduce the conducted and radiated EMI,
while the LM25088-2 provides a versatile restart timer
for overload protection. Additional features include a
low dropout bias regulator, tri-level enable input to
control shutdown and standby modes, soft-start and
oscillator synchronization capability. The device is
available in a thermally enhanced HTSSOP-16 pin
package.
Device Information
(1)
PART NUMBER
LM25088
LM25088-Q1
PACKAGE
HTSSOP (16)
HTSSOP (16)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
5.00 mm × 4.40 mm
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LM25088Q is an Automotive Grade Product that is
AEC-Q100 Grade 1 Qualified (-40°C to +125°C
Operating Junction Temperature)
Emulated Current Mode Control
Drives External High-Side N-Channel MOSFET
Ultra-Wide Input Voltage Range from 4.5V to 42V
Low I
Q
Shutdown and Standby Modes
High Duty Cycle Ratio Feature for Reduced
Dropout Voltage
Spread Spectrum EMI Reduction (LM25088-1)
Hiccup Timer for Overload Protection (LM25088-
2)
Adjustable Output Voltage from 1.205 V with 1.5%
Feedback Reference Accuracy
Wide Bandwidth Error Amplifier
Single Resistor Oscillator Frequency Setting
Oscillator Synchronization Capability
Programmable Soft-Start
High Voltage, Low Dropout Bias Regulator
Thermal Shutdown Protection
Package: HTSSOP 16-Pin
2 Applications
•
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Automotive Infotainment
Automotive USB Accessory Adapters
Industrial DC-DC Bias and Motor Drivers
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Simplified Schematic
VIN (4.5V-42V)
R
UV2
EN
C
IN
R
UV1
DITH/RES
C
DITHER/RESTART
Typical Application Circuit Efficiency
VIN
BOOT
HG
SW
D
CS
Rs
RAMP
CSG
OUT
FB
R
COMP
GND
COMP
C
COMP
C
OUT1
C
OUT2
R
FB2
R
FB1
C
BOOT
Q
L
VOUT
LM25088
VCC
R
RAMP
C
VCC
C
RAMP
C
SS
R
RT
SS
RT/SYNC
C
HF
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.
LM25088, LM25088-Q1
SNVS609J – DECEMBER 2008 – REVISED JANUARY 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features
..................................................................
Applications
...........................................................
Description
.............................................................
Simplified Schematic.............................................
Revision History.....................................................
Pin Configuration and Functions
.........................
Specifications.........................................................
7.1
7.2
7.3
7.4
7.5
7.6
Absolute Maximum Ratings ......................................
Handling Ratings.......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
1
1
1
1
2
3
5
5
5
5
5
6
8
8.4 Device Functional Modes........................................
19
9
Application and Implementation
........................
20
9.1
9.2
9.3
9.4
Application Information............................................
Typical Application ..................................................
Design Requirements..............................................
Detailed Design Procedure .....................................
20
20
20
20
10 Power Supply Recommendations
.....................
29
10.1 Thermal Considerations ........................................
29
11 Layout...................................................................
32
11.1 Layout Guidelines .................................................
32
11.2 Layout Example ....................................................
32
12 Device and Documentation Support
.................
33
12.1
12.2
12.3
12.4
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
33
33
33
33
8
Detailed Description
............................................
10
8.1 Overview .................................................................
10
8.2 Functional Block Diagram .......................................
10
8.3 Feature Description.................................................
11
13 Mechanical, Packaging, and Orderable
Information
...........................................................
33
5 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision I (June 2014) to Revision J
•
Page
Changed "LM5088" to "LM25088" in caption for
Figure 13
.................................................................................................
10
Changes from Revision H (March 2013) to Revision I
•
Page
Changed Added, updated, or renamed the following sections: Device Information Table,
Specifications Application
and Implementation; Power Supply Recommendations; Layout; Device and Documentation Support; Mechanical,
Packaging, and Ordering Information.
Added Layout Guidelines and Layout Example. .......................................................
1
Changed × to - in
Equation 2
...............................................................................................................................................
13
Added kΩ in
Timing Resistor................................................................................................................................................ 20
Deleted "/A" in the numerator of
Equation 11
.....................................................................................................................
22
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Changes from Revision G (March 2013) to Revision H
•
Page
Changed layout of National Data Sheet to TI format .............................................................................................................
1
2
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Copyright © 2008–2015, Texas Instruments Incorporated
Product Folder Links:
LM25088 LM25088-Q1
LM25088, LM25088-Q1
www.ti.com
SNVS609J – DECEMBER 2008 – REVISED JANUARY 2015
6 Pin Configuration and Functions
LM25088-1 16 Pin
PWP Package (Dither Version)
(Top View)
VIN
VCC
EN
BOOT
SS
HG
RAMP
SW
HTSSOP-16
RT
CS
GND
CSG
EP
COMP
DITH
FB
OUT
LM25088-2 16 Pin
PWP Package (Restart Version)
(Top View)
VIN
VCC
EN
BOOT
SS
HG
RAMP
SW
HTSSOP-16
RT
CS
GND
CSG
EP
COMP
RES
FB
OUT
Copyright © 2008–2015, Texas Instruments Incorporated
Submit Documentation Feedback
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Product Folder Links:
LM25088 LM25088-Q1
LM25088, LM25088-Q1
SNVS609J – DECEMBER 2008 – REVISED JANUARY 2015
www.ti.com
Pin Functions
PIN
NUMBER
1
NAME
VIN
DESCRIPTION
Input supply voltage
APPLICATION INFORMATION
IC supply voltage. The operating range is 4.5V to 42V.
If the EN pin voltage is below 0.4V the regulator will be in a low power
state. If the EN pin voltage is between 0.4V and 1.2V the controller will be
in standby mode. If the EN pin voltage is above 1.2V the controller will be
operational. An external voltage divider can be used to set a line under
voltage shutdown threshold. If the EN pin is left open, a 5µA pull-up
current forces the pin to the high state and enables the controller.
When SS is below the internal 1.2V reference, the SS voltage will control
the error amplifier. An internal 11 µA current source charges an external
capacitor to set the start-up rate of the controller. The SS pin is held low in
the standby, VCC UV and thermal shutdown states. The SS pin can be
used for voltage tracking by connecting this pin to a master voltage supply
less than 1.2V. The applied voltage will act as the reference for the error
amplifier.
An external capacitor connected between this pin and the GND pin sets
the ramp slope used for emulated current mode control. Recommended
capacitor range 100 pF to 2000 pF. See the
Application and
Implementation
section for selection of capacitor value.
The internal oscillator is programmed with a single resistor between this
pin and the GND pin. The recommended frequency range is 50 kHz to 1
MHz. An external synchronization signal, which is higher in frequency than
the programmed frequency, can be applied to this pin through a small
coupling capacitor. The RT resistor to ground is required even when using
external synchronization.
Ground return.
2
EN
Enable input
3
SS
Soft-start
4
RAMP
Ramp control signal
5
RT/SYNC
Internal oscillator
frequency set input and
synchronization input
Ground
6
7
8
9
GND
COMP
FB
OUT
Output of the internal error The loop compensation network should be connected between this pin
amplifier
and the FB pin.
Feedback signal from the
regulated output
This pin is connected to the inverting input of the internal error amplifier.
The regulation threshold is 1.205V.
A capacitor connected between DITH pin and GND is charged and
discharged by 27 µA current sources. As the voltage on the DITH pin
ramps up and down, the oscillator frequency is modulated between -5% to
+5% of the nominal frequency set by the RT resistor. Grounding the DITH
pin will disable the frequency dithering mode.
The RES pin is normally connected to an external capacitor that sets the
timing for hiccup mode current limiting. In normal operation, a 25 µA
current source discharges the RES pin capacitor to ground. If cycle-by-
cycle current limit threshold is exceeded during any PWM cycle, the
current sink is disabled and RES capacitor is charged by an internal 50 µA
current. If the RES voltage reaches 1.2V, the HG pin gate drive signal will
be disabled and the RES pin capacitor will be discharged by a 1 µA
current sink. Normal operation will resume when the RES pin falls below
0.2V.
Low side reference for the current sense resistor.
Current measurement connection for the re-circulating diode. An external
sense resistor and an internal sample/hold circuit sense the diode current
at the conclusion of the buck switch off-time. This current measurement
provides the DC offset level for the emulated current ramp.
Connect to the source terminal of the external MOSFET switch.
Connect to the gate terminal of the external MOSFET switch.
An external capacitor is required between the BOOT and the SW pins to
provide bias to the MOSFET gate driver. The capacitor is charged from
VCC via an internal diode during the off-time of the buck switch.
VCC tracks VIN up to the regulation level (7.8V Typ). A 0.1 µF to 10 µF
ceramic decoupling capacitor is required. An external voltage between
8.3V and 13V can be applied to this pin to reduce internal power
dissipation.
Output voltage connection Connect directly to the regulated output voltage.
Frequency Dithering
(LM25088-1 Only)
10
DITH
10
RES
Hiccup Mode Restart
(LM25088-2 Only)
11
12
13
14
15
CSG
CS
SW
HG
BOOT
Current Sense Ground
Current sense
Switching node
High Gate
Input for bootstrap
capacitor
Output of the bias
regulator
16
VCC
4
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Copyright © 2008–2015, Texas Instruments Incorporated
Product Folder Links:
LM25088 LM25088-Q1
LM25088, LM25088-Q1
www.ti.com
SNVS609J – DECEMBER 2008 – REVISED JANUARY 2015
7 Specifications
7.1 Absolute Maximum Ratings
(1) (2)
over operating free-air temperature range (unless otherwise noted)
MIN
VIN, VOUT to GND
BOOT to GND
SW to GND
VCC to GND
HG to SW
EN to GND
BOOT to SW
CS, CSG to GND
All other inputs to GND
Junction Temperature
(1)
(2)
–0.3
–0.3
–0.3
–2
–0.3
–0.3
MAX
45
60
45
16
BOOT+0.3
14
16
0.3
7
+150
UNIT
v
V
V
V
V
V
V
V
V
°C
Absolute Maximum Ratings are limits beyond which damage to the device may occur.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
7.2 Handling Ratings
MIN
T
stg
V
(ESD)
(1)
(2)
Storage temperature range
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins
(1) (2)
−65
MAX
+150
2
UNIT
°C
kV
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
7.3 Recommended Operating Conditions
(1)
over operating free-air temperature range (unless otherwise noted)
MIN
VIN Voltage
VCC Voltage (externally supplied)
Operation Junction Temperature
(1)
4.5
8.3
–40
MAX
42
13
+125
UNIT
V
V
°C
Operating Ratings are conditions under which operation of the device is intended to be functional. For ensured specifications and test
conditions, see the Electrical Characteristics.
7.4 Thermal Information
LM25088(Q1)
THERMAL METRIC
(1)
R
θJA
R
θJC(bot)
(1)
Junction-to-ambient thermal resistance
Junction-to-case (bottom) thermal resistance
PWP
16 PINS
40
6
°C/W
UNIT
For more information about traditional and new thermal metrics, see the
IC Package Thermal Metrics
application report,
SPRA953.
Copyright © 2008–2015, Texas Instruments Incorporated
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