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LM2797 Datasheet Preview

LM2797 Datasheet

Voltage Converter

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OBSOLETE
LM2797, LM2798
www.ti.com
SNVS199C – MAY 2004 – REVISED SEPTEMBER 2011
LM2797/LM2798 120mA High Efficiency Step-Down Switched Capacitor Voltage Converter
with Voltage Monitoring
Check for Samples: LM2797, LM2798
FEATURES
1
2 Output Voltage Options:
– 2.0V ± 5%, 1.8V ± 5%, and 1.5V ± 6%
• 120mA Output Current Capability
• Multi-Gain and Gain Hopping for Highest
Possible Efficiency - up to 90% Efficient
• 2.6V to 5.5V Input Range
• Input and Output Voltage Monitoring (BATOK
and POK)
• Low Operating Supply Current: 35µA
• Shutdown Supply Current: 0.1µA
• Thermal and Short Circuit Protection
• LM2798 Turn-on Time: 400µs
– LM2797 Turn-on Time: 100µs
• Available in an 10-Pin VSSOP Package
APPLICATIONS
• Cellular Phones
• Pagers
• H/PC and P/PC Devices
• Portable Electronic Equipment
• Handheld Instrumentation
DESCRIPTION
The LM2797/98 switched capacitor step-down DC/DC
converters efficiently produce a 120mA regulated low-
voltage rail from a 2.6V to 5.5V input. Fixed output
voltage options of 1.5V, 1.8V, and 2.0V are available.
The LM2797/98 uses multiple fractional gain
configurations to maximize conversion efficiency over
the entire input voltage and output current ranges.
Also contributing to high overall efficiency is the
extremely low supply current of the LM2797/98: 35µA
operating unloaded and 0.1µA in shutdown.
Features of the LM2797/98 include input voltage and
output voltage monitoring. Pin BATOK provides
battery monitoring by indicating when the input
voltage is above 2.85V (typ.). Pin POK verifies that
the output voltage is not more than 5% (typ.) below
the nominal output voltage of the part.
The optimal external component requirements of the
LM2797/98 solution minimize size and cost, making
the part ideal for Li-Ion and other battery powered
designs. Two 1µF flying capacitors and two 10µF
bypass capacitors are all that is required, and no
inductors are needed.
The LM2797/98 also features short-circuit protection
over-temperature protection, and soft-start circuitry to
prevent excessive inrush currents. The LM2798 has a
400µs turn-on time. The turn-on time of the LM2797
is 100µs.
Typical Application Circuit
LM2797/98
VIN
2.6V - 5.5V
4
VIN
1
VOUT
VDD or VIN
1 M:
10PF
3
1PF C1+
2
C1-
7
EN
C2+
C2-
POK
8
10
5
6
BATOK
9
GND
Capacitors: 1.0 PF - TDK C1608X5R1A105K
10 PF - TDK C2012X5R0J106M
VOUT = 1.5V, 1.8V, or 2.0V*
IOUT up to 120mA
1PF 10PF
1 M:
*LM2797: VOUT = 1.8V only
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 © 2004–2011, Texas Instruments Incorporated




etcTI

LM2797 Datasheet Preview

LM2797 Datasheet

Voltage Converter

No Preview Available !

LM2797, LM2798
SNVS199C – MAY 2004 – REVISED SEPTEMBER 2011
Connection Diagram
OBSOLETE
www.ti.com
VOUT
C1-
C1+
VIN
POK
1
2
3
4
5
10 C2-
9 GND
8 C2+
7 EN
6 BATOK
Figure 1. LM2797/98
VSSOP-10 Package
NS Package #: DGS0010A
Top View
PIN DESCRIPTIONS
Pin Name
Description
1
VOUT
Regulated Output Voltage
2 C1- First Flying Capacitor: Negative Terminal
3 C1+ First Flying Capicitor: Positive terminal
4 VIN Input Voltage. Recommended VIN Range: 2.6V to 5.5V
5
POK
Power-OK Indicator: Output voltage sense. Open-drain NFET output. With an external pull-up
resistor tied to POK, V(POK) will be high when VOUT is regulating correctly. When VOUT falls
out of regulation, the internal open-drain FET pulls the POK voltage low.
6
BATOK
Battery-OK Indicator: Input voltage sense. Open-drain NFET output. With an external pull-up
resistor tied to BATOK, V(BATOK) will be high when VIN > 2.85V (typ). LM2797/98 pulls
V(BATOK) low when VIN < 2.65V (typ.) , and/or when the part is in shutdown [V(EN) = 0].
7 EN Enable Logic Input. High voltage = ON, Low voltage = SHUTDOWN
8 C2+ Second Flying Capacitor: Positive Terminal
9
GND
Ground Connection
10 C2- Second Flying Capacitor: Negative Terminal
2 Submit Documentation Feedback
Copyright © 2004–2011, Texas Instruments Incorporated
Product Folder Links: LM2797 LM2798


Part Number LM2797
Description Voltage Converter
Maker etcTI
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