Document
October 2002 www.DataSheet4U.com
LM2788 120mA High Efficiency Step-Down Switched Capacitor Voltage Converter
LM2788 120mA High Efficiency Step-Down Switched Capacitor Voltage Converter
General Description
The LM2788 switched capacitor step-down DC/DC converter efficiently produces 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 LM2788 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 LM2788: 32µA operating unloaded and 0.1µA in shutdown. The optimal external component requirements of the LM2788 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 are required, and no inductors are needed. The LM2788 also features noise-reducing soft-start circuitry, short-circuit protection and over-temperature protection.
Features
n Output voltage options: 2.0V ± 5%, 1.8V ± 5%, 1.5V ± 6% n 120mA output current capability n Multi-Gain and Gain Hopping for Highest Possible Efficiency - up to 90% Efficient n 2.6V to 5.5V input range n Low operating supply current: 32µA n Shutdown supply current: 0.1µA n Thermal and short circuit protection n Available in an 8-Pin MSOP Package
Applications
n n n n n Cellular Phones Pagers H/PC and P/PC Devices Portable Electronic Equipment Handheld Instrumentation
Typical Application Circuit
20044401
© 2002 National Semiconductor Corporation
DS200444
www.national.com
LM2788
Connection Diagram
LM2788 Mini SO-8 (MSOP-8) Package NS Package #: MUA08A
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20044402
Top View
Pin Description
Pin 1 2 3 4 5 6 7 8 Name VOUT C1C1+ VIN EN C2+ GND C2Regulated Output Voltage First Flying Capacitor: Negative Terminal First Flying Capicitor: Positive terminal Input voltage. Recommended VIN Range: 2.6V to 5.5V Enable. Logic Input. High voltage = ON, Low voltage = SHUTDOWN Second Flying-Capacitor: Positive Terminal Ground Connection Second Flying Capacitor: Negative Terminal Description
Ordering Information
Output Voltage 1.50V 1.80V 2.00V Ordering Information LM2788MM-1.5 LM2788MMX-1.5 LM2788MM-1.8 LM2788MMX-1.8 LM2788MM-2.0 LM2788MMX-2.0 MSOP-8 Package Type Package Marking S30B S30B S23B S23B S24B S24B Supplied as 1000 units on Tape-and Reel 3500 units onTape-and-Reel 1000 units on Tape-and Reel 3500 units on Tape-and Reel 1000 units on Tape-and Reel 3500 units on Tape-and Reel
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2
LM2788
Absolute Maximum Ratings
2)
(Notes 1,
Operating Ratings
Input Voltage Range Recommended Output Current Range Junction Temperature Range Ambient Temperature Range (Note 6)
www.DataSheet4U.com (Notes 1, 2)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN, EN pins: Voltage to Ground (Note 3) Junction Temperature (TJ-MAX-ABS) Continuous Power Dissipation (Note 4) VOUT Short-Circuit to GND Duration (Note 4) Storage Temperature Range Lead Temperature (Soldering, 5 Sec.) ESD Rating (Note 5) Human-body model: Machine model −0.3V to 5.6V 150˚C Internally Limited Unlimited −65˚C to 150˚C 260˚C 2 kV 200V
2.6V to 5.5V 0mA to 120mA -40˚C to 125˚C -40˚C to 85˚C
Thermal Information
Junction-to-Ambient Thermal Resistance, MSOP-8 Package (θJA) (Note 7) 220˚C/W
Electrical Characteristics (Notes 2, 8) Limits in standard typeface and typical values apply for TJ = 25oC. Limits in boldface type apply over the operating junction temperature range. Unless otherwise specified: 2.6 ≤ VIN ≤ 5.5V, V(EN) = VIN, C1 = C2 = 1µF, CIN = COUT = 10µF. (Note 9)
Symbol Parameter Conditions 2.8V ≤ VIN ≤ 4.2V 0mA ≤ IOUT ≤ 120mA 4.2V ≤ VIN ≤ 5.5V 0mA ≤ IOUT ≤ 120 mA 2.8V ≤ VIN ≤ 4.2V 0mA ≤ IOUT ≤ 120 mA 4.2V ≤ VIN ≤ 5.5V 0mA ≤ IOUT ≤ 120mA IOUT = 0mA V(EN) = 0V LM2788-1.8: VIN = 3.6V, IOUT = 120mA LM2788-1.8: VIN = 3.0V, IOUT = 60mA LM2788-1.5: 3.0 ≤ VIN ≤ 4.2V, IOUT = 60mA LM2788-1.8: 3.0 ≤ VIN ≤ 4.2V, IOUT = 60mA LM2788-2.0: 3.0 ≤ VIN ≤ 4.2V, IOUT = 60mA VIN = 3.6V, IOUT = 120mA (Note 12) VIN = 3.6, VOUT = 0V 0.9 0 VEN = 0V VEN = 5.5V 0 30 Min -5 -6 Typ Max +5 +6 Units LM2788-1.8, LM2788-2.0 % of VOUT (nom)
(Note 10)
VOUT
Output Voltage Tolerance
LM2788-1.5 -6 -6 +6 +6 % of VOUT (nom)
(Note 10)
VOUT
Output Voltage Tolerance
All Output Voltage Options IQ I
SD
Operating Supply Current Shutdown Supply Current Output Voltage Ripple Peak Efficiency Average Efficiency over Li-Ion Input Voltage Range (Note 11) Turn-On Time Switching Frequency Short-Circuit Current EN pin Logic-High Input EN pin Logic-Low Input EN pin input current
32 0.1 20 90 76 82 75 0.4 500 25
50 2
µA µA mVp-p % % ms kHz mA
VR EPEAK EAVG tON fSW ISC VIH VIL IEN
Enable Pin (EN) Characteristics VIN 0.4 V V nA
Note 1: Absolute Maximum Ratings indicate.