TPS61251 Datasheet, PDF (1/21 Pages) Texas Instruments – BOOST CONVERTER FOR BATTERY BACKUP CHARGING WITH ADJUSTABLE CONSTANT CURRENT AND SNOOZE MODE

TPS61251
www.ti.com
SLVSAF7 – SEPTEMBER 2010
BOOST CONVERTER FOR BATTERY BACKUP CHARGING WITH ADJUSTABLE
CONSTANT CURRENT AND SNOOZE MODE
Check for Samples: TPS61251
FEATURES
1
• Resistor Programmable Input Current Limit
– ±10% Current Accuracy at 500mA over Full
Temperature Range
– Programmable from 100mA up to 1500mA
• Snooze Mode Draws Only 2 mA (typ.)
Quiescent Current
• Designed to Charge Large Capacitor Values in
the Farad Range
• Up to 92% Efficiency
• Power Good Indicates Appropriate Output
Voltage Level even in Shut Down
• V_IN Range from 2.3V to 6.0V
• Adjustable Output Voltage up to 6.5V
• 100% Duty-Cycle Mode When V_IN > V_OUT
• Load Disconnect and Reverse Current
Protection
• Short Circuit Protection
• Typical Operating Frequency 3.5 MHz
• Available in a 2×2-mm QFN-8 Package
APPLICATIONS
• Current Limited Applications With High Peak
Power Loads (SSD, PCMCIA Tx Bursts,
Memory, GPRS/GSM Tx)
• Li-Ion Applications
• Battery Backup Applications
• Audio Applications
• RF-PA Buffer
DESCRIPTION
The TPS61251 device provides a power supply solution for products powered by either a three-cell, NiCd or
NiMH battery, or a one-cell Li-Ion or Li-polymer battery. The wide input voltage range is ideal to power portable
applications like mobile phones, solid state drives (SSD) and wireless modems. The converter is designed to
charge large capacitors in the Farad range to support battery back up applications. During capacitor charging the
TPS61251 is working as a constant current source until V_OUT has reached its programmed value. The charge
current can be programmed by an external resistor R_ILIM and provides a ±10% accuracy for the average input
current limit.
The TPS61251 in combination with a reservoir capacitor allows the converter to provide high current pules that
would exceed the capability of the suppling circuit (PC slot, USB) and keeps the slot power safely within its
capabilities. During light loads the device will automatically enters an enhanced power save mode (Snooze
Mode), which allows the converter to maintain the required output voltage, while only drawing 2 mA from the
battery. This will allow maximum efficiency at lowest quiescent currents.
TPS61251 allows the use of small inductors and input capacitors to achieve a small solution size. During
shutdown, the load is completely disconnected from the battery and will not discharge either the battery nor the
charged bulk capacitor. The TPS61251 is available in a 8-pin QFN package measuring 2×2 mm (DSG).
V_IN
2.3 V to
6.0 V
L1
1 μH
C1
10 µF
R_ILIM
20 kΩ
L
VOUT
VIN
EN
FB
ILIM
GND
PG
TPS61251
R1
1 MΩ
R2
280 kΩ
C_FF
1 nF
R4
1 MΩ
C_OUT
4.7 µF
V_OUT
5.5 V
C_BULK
>150 µF
Power Good
Output
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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.
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 © 2010, Texas Instruments Incorporated