LM2781TPX/NOPB [TI]
IC SWITCHED CAPACITOR CONVERTER, 400 kHz SWITCHING FREQ-MAX, PBGA8, CSP-8, Switching Regulator or Controller;
| 型号： | LM2781TPX/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | IC SWITCHED CAPACITOR CONVERTER, 400 kHz SWITCHING FREQ-MAX, PBGA8, CSP-8, Switching Regulator or Controller 开关 |
| 文件： | 总8页 (文件大小：212K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OBSOLETE
LM2781
www.ti.com
SNVS201B –MAY 2004–REVISED MAY 2004
LM2781 Ultra-Low Ripple Switched Capacitor Voltage Inverter
Check for Samples: LM2781
1
FEATURES
DESCRIPTION
The LM2781 is a charge pump that inverts an input
2
•
•
Inverts Input Voltage
voltage in the range of 1.8V to 5.5V to the
corresponding output voltage of -1.8V to -5.5V. With
use of three or four low-cost external ceramic
capacitors, the LM2781 can provide up to 50mA of
output current.
Ultra-Low Voltage Ripple and 8Ω Typical
Output Resistance with Two Flying Capacitors
•
Output Resistance of 18Ω Using One Flying
Capacitor
•
•
210kHz (typ.) Switching Frequency
The LM2781 operates at a 210kHz typical switching
frequency to minimize supply current (0.7mA typ.).
Two charge pumps operate 180° out of phase to
significantly reduce the output voltage ripple
compared to that of traditional single-phase charge
pump circuits. If larger output ripple can be tolerated,
optional capacitor C2 may be omitted to reduce the
cost and size of the solution. The LM2781 is available
in an 8-pin DSBGA chip-scale package.
8-pin DSBGA Package (1.4mm × 1.4mm ×
0.5mm)
APPLICATIONS
•
•
•
•
•
•
Cellular Phones
Pagers
PDAs
See also: LM2780, a slow clock (12kHz typ) version
of this topology with extremely low supply current.
Op-Amp Power Supplies
Interface Power Supplies
Handheld Instruments
Typical Application Circuit
C2 * : 1 mF
* Capacitor C2 optional. Use for
extremely low output voltage ripple
and improved output resistance.
C2+
SD
B1
C2-
LM2781
A1
C1
A2
C2
A3
C3
VIN
1.8V to 5.5V
B3
VOUT = -VIN
CIN
COUT
1 mF
1 mF
C1+
C1-
C1: 1 mF
1
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.
All trademarks are the property of their respective owners.
2
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 © 2004, Texas Instruments Incorporated
OBSOLETE
LM2781
SNVS201B –MAY 2004–REVISED MAY 2004
www.ti.com
Connection Diagram
C2-
A3
VOUT
B3
C1-
C3
VOUT
B3
C1-
C3
C2-
A3
A2
SD
C2
C2
A2
SD
GND
GND
A1
C2+
B1
VIN
C1
C1+
C1
C1+
B1
VIN
A1
C2+
Bottom View
Top View
Figure 1. 8-Bump Thin DSBGA Package
Package Number YPB0008
PIN DESCRIPTION
Description
Pin
A1
B1
C1
A2
C2
A3
B3
C3
Name
C2+
VIN
Secondary flying-capacitor connection
Input voltage. Input range: 1.8V to 5.5V
Primary flying-capacitor connection
Shutdown pin logic input. Low = on, High = shutdown
Ground
C1+
SD
GND
C2-
Secondary flying-capacitor connection
Output voltage. VOUT = -VIN
VOUT
C1-
Primary flying capacitor connection
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.
Absolute Maximum Ratings(1)(2)
VIN pin: Voltage to GND
−0.3V to 5.8V
-0.3V to (VIN + 0.3V), with
5.8V max
SD pin: Voltage to GND
Output Short-to-GND Duration(3)
Maximum Junction Temperature (TJ-MAX
Storage Temperature Range
1 sec.
150°C
)
-65°C to +150°C
265°C
Pad Temperature (Soldering, 10 sec.)
Human-body model
Machine model
2kV
ESD Rating(4)
200V
(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits
and associated test conditions, see the Electrical Characteristics table.
(2) All voltages are with respect to the potential at the GND pin.
(3) VOUT may be shorted to GND for one second without damage when the ambient temperature is at or below 85°C. Prolonged or
repeated shorts of VOUT to GND may damage the device, and should be avoided.
(4) The human-body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF
capacitor discharged directly into each pin.
Operating Ratings(1) (2)
(1) Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under
which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits
and associated test conditions, see the Electrical Characteristics table.
(2) All voltages are with respect to the potential at the GND pin.
2
Submit Documentation Feedback
Copyright © 2004, Texas Instruments Incorporated
Product Folder Links: LM2781
OBSOLETE
LM2781
www.ti.com
SNVS201B –MAY 2004–REVISED MAY 2004
Operating Ratings(1) (2) (continued)
Input Voltage Range
1.8V to 5.5V
-40°C to +90°C
-40°C to +85°C
Junction Temperature (TJ) Range
Ambient Temperature (TA) Range(3)
(3) Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 90°C), the maximum
power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part in the application
(θJA), as given by the following equation: TA-MAX = TJ-MAX-OP - (θJA × PD-MAX).
Thermal Properties
(1)
Junction-to-Ambient Thermal Resistance (θJA
)
220°C/W
(1) Junction-to-ambient thermal resistance of the DSBGA package is highly application and board-layout dependent.
Electrical Characteristics(1)(2)
Limits in standard typface are for TJ = 25°C, and limits in boldface type apply over the full operating junction temperature
range (-40°C ≤ TJ ≤ +90°C). Unless otherwise noted: specifications apply to the LM2781 Typical Application Circuit (pg. 1)
with VIN = 5.0V, V(SD) = 0V, and CIN = COUT = C1 = C2 = 1µF.(3)
Symbol
ROUT
Parameter
Output Resistance(4)
Conditions
IOUT = 10mA, C2 = 1µF
Min
Typ
8
Max
30
Units
Ω
IOUT = 10mA, C2 removed
No load
18
40
Ω
IQ
Supply Current
0.7
0.1
210
1.4
0.5
400
mA
µA
ISD
FSW
VSD
Shutdown Supply Current
Switching Frequency
Shutdown Pin Logic Levels
V(SD) = 5.0V
100
0
kHz
Normal Operation
1.8V ≤ VIN ≤ 5.5V
0.5
VIN
V
Shutdown Mode
0.5×VIN
1.8V ≤ VIN ≤ 5.5V
VOUTp-p
PEFF
Output Voltage Ripple
Power Efficiency
VIN = 5.0V, IOUT = 10mA
VIN = 5.0V, IOUT = 10mA
10
92
mV
%
(1) All voltages are with respect to the potential at the GND pin.
(2) Max and Min limits are specified by design, test, or statistical analysis. Typical numbers are not ensured, but do represent the most
likely norm.
(3) CIN, COUT, C1, and C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics.
(4) Output resistance is a model for the voltage drop at the output, resulting from internal switch resistance, capacitor ESR, and charge
pump charge transfer characteristics. Output voltage can be predicted with the following equation: VOUT = -[VIN - (IOUT × ROUT)]
Copyright © 2004, Texas Instruments Incorporated
Submit Documentation Feedback
3
Product Folder Links: LM2781
OBSOLETE
LM2781
SNVS201B –MAY 2004–REVISED MAY 2004
www.ti.com
Typical Performance Characteristics
Unless otherwise specified, TA = 25°C, CIN = COUT = C1 = C2 = 1µF.
Output Voltage vs. Load Current
Power Efficiency vs. Load Current
Figure 2.
Figure 3.
Output Resistance vs. Temperature (IOUT = 10mA)
Supply Current vs. Temperature (IOUT = 0)
Figure 4.
Figure 5.
Switching Frequency vs. Temperature
Output Voltage Ripple vs. Output Current
Figure 6.
Figure 7.
4
Submit Documentation Feedback
Copyright © 2004, Texas Instruments Incorporated
Product Folder Links: LM2781
OBSOLETE
LM2781
www.ti.com
SNVS201B –MAY 2004–REVISED MAY 2004
Block Diagram
C1
LM2781
C1+
C1-
CLK1A
S1A
CLK1A
S1B
VIN
.
CIN
CLK1B
CLK1B
VOUT
S1C
S1D
.
CLK1A
CLK1B
COUT
Charge Pump 1
f1
f2
SD
CLK
GEN
Charge Pump 2
CLK2A
CLK2B
CLK2A
CLK2A
S2A
S2B
CLK2B
CLK2B
S2C
S2D
GND
C2+
C2-
C2
Copyright © 2004, Texas Instruments Incorporated
Submit Documentation Feedback
5
Product Folder Links: LM2781
OBSOLETE
LM2781
SNVS201B –MAY 2004–REVISED MAY 2004
www.ti.com
OPERATION DESCRIPTION
The LM2781 is a switched capacitor voltage inverter that produces a negative output voltage from a positive
input voltage. To minimize output voltage ripple, the LM2781 contains two charge pump inverters that operate
180° out of phase. These two charge pumps can be seen in the block diagram above.
A basic switched capacitor inverter is a two-phase charge pump circuit that transfers charge from the input to the
output using a flying capacitor. Charge Pump 1 in the block diagram will be used to illustrate the operation of a
single charge pump. Disregard Charge Pump 2 in the diagram for now. In phase 1 (φ1), the CLK1A signal of
Charge Pump 1 is high, and MOSFET switches S1A and S1B are ON. For Charge Pump 1, this is the charge
phase, as the flying capacitor C1 is charged to the input voltage. In the second phase (φ2), the positive-charged
plate of C1 is connected to GND through switch S1C, and the negative-charged plate is connected to the output
through switch S1D. This results in the output voltage being approximately equal in magnitude to the input
voltage, but opposite in sign (VOUT ~= - VIN). In this pump phase, charge stored on the flying capacitor supplies
the current to the load and transfers charge to the output capacitor.
This basic inverter has ripple in the output voltage. During the charge phase, the load current is supplied by the
charge on the output capacitor. As charge is pulled off COUT, the voltage across the capacitor drops, and the
magnitude of the output voltage ( |VOUT| ) falls. During the pump phase, the flying capacitor transfers charge to
the COUT, elevating both the voltage across the COUT and the magnitude of the output voltage.
The LM2781 contains two charge pump inverters running 180° out of phase. Notice in the block diagram that the
clock connections on Charge Pump 2 are opposite of the clock connections to Charge Pump 1. Thus, when
Charge Pump 1 is in the charge phase, Charge Pump 2 is in the pump phase, and vice-versa. With this double-
pump technology, there is always a flying capacitor connected to the output. This results in significantly lower
output voltage ripple than that of a single-pump inverter.
OUTPUT VOLTAGE RIPPLE
Several factors influence the magnitude of voltage ripple on the output of the LM2781. Primary influences are
output capacitance, flying capacitance, load current, input voltage, and output capacitor ESR.
The magnitude of the output voltage ripple is difficult to predict with equations when the LM2781 is double
pumping. Refer to the Typical Performance Characteristic curves for this information. In general, ripple decreases
with increased output capacitance, decreased load current, a lower input voltage, a smaller flying capacitance
and/or a smaller output capacitor ESR.
When only one charge pump is active (C2 removed), the output ripple is more predictable, and can be estimated
with the following equation:
VRIPPLE = [(0.5×IOUT) / (fSW×COUT) ] + (2×IOUT×ESRCout
)
OUTPUT RESISTANCE
Output resistance (ROUT) models the internal non-idealities of a charge pump that result in droop in the output
voltage. The effect of output resistance on output voltage is expressed in the following equation:
VOUT = - [VIN - ( |IOUT| × ROUT )]
Output resistance is a function of the internal switch resistance (RSW) , flying capacitance (C1), flying capacitor
equivalent series resistance (ESRC1), output capacitor ESR (ESRCout), and internal switching frequency (fSW).
When the LM2781 operates as a single charge pump (C2 removed), the output resistance can be approximated
by the following equation:
1 Fly Cap: ROUT1 ~= 2RSW1+[1/(fSW*C1)]+4ESRC1+ESRCout
RSW1 is the sum of the ON resistance of the four internal MOSFET switches of Charge Pump 1.
With both C1 and C2 in place, the double pumping topology of the LM2781 cuts the output resistance in half:
2 Fly Caps: ROUT2 ~= 0.5×ROUT1
Recommendations for minimizing output resistance include increasing flying capacitance and minimizing output
and flying capacitor ESR.
6
Submit Documentation Feedback
Copyright © 2004, Texas Instruments Incorporated
Product Folder Links: LM2781
OBSOLETE
LM2781
www.ti.com
SNVS201B –MAY 2004–REVISED MAY 2004
CAPACITOR SELECTION
Surface-mount multi-layer ceramic capacitors are recommended for use with the LM2781. These capacitors are
small, inexpensive and have very low equivalent series resistance (ESR, < 15mΩ typ.). Tantalum capacitors, OS-
CON capacitors, and aluminum electrolytic capacitors generally are not recommended for use with the LM2781
due to their high ESR, as compared to ceramic capacitors.
For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with
the LM2781. These capacitors have tight capacitance tolerance (as good as ±10%), hold their value over
temperature (X7R: ±15% over -55°C to 125°C; X5R: ±15% over -55°C to 85°C), and typically have little voltage
coefficient.
Capacitors with Y5V and/or Z5U temperature characteristic are generally not recommended for use with the
LM2781. These types of capacitors typically have wide capacitance tolerance (+80%, -20%), vary significantly
over temperature (Y5V: +22%, -82% over -30°C to +85°C range; Z5U: +22%, -56% over +10°C to +85°C range),
and have poor voltage coefficients. Under some conditions, a nominal 1µF Y5V or Z5U capacitor could have a
capacitance of only 0.1µF. Such deviation would severely affect performance of the LM2781 circuit.
Copyright © 2004, Texas Instruments Incorporated
Submit Documentation Feedback
7
Product Folder Links: LM2781
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Automotive and Transportation www.ti.com/automotive
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
www.ti.com/industrial
www.ti.com/medical
Medical
Logic
Security
www.ti.com/security
Power Mgmt
Microcontrollers
RFID
power.ti.com
Space, Avionics and Defense
Video and Imaging
www.ti.com/space-avionics-defense
www.ti.com/video
microcontroller.ti.com
www.ti-rfid.com
www.ti.com/omap
OMAP Applications Processors
Wireless Connectivity
TI E2E Community
e2e.ti.com
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2013, Texas Instruments Incorporated
相关型号：
©2020 ICPDF网 联系我们和版权申明