Document
LM2794, LM2795
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SNVS168L – JANUARY 2002 – REVISED MAY 2013
LM2794 /LM2795 Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control
Check for Samples: LM2794, LM2795
FEATURES
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•2 Regulated Current Sources with ±0.5% Matching between any Two Outputs
• High Efficiency 3/2 Boost Function • Drives One, Two, Three or four White LEDs • 2.7V to 5.5V Input Voltage • Up to 80mA Output Current • Analog Brightness Control • Active-Low or High Shutdown Input ('94/95) • Very Small Solution Size and no Inductor • 2.3µA (typ.) Shutdown Current • 325kHz Switching Frequency (min.) • Constant Frequency Generates Predictable
Noise Spectrum • Thin DSBGA Package: 2.08mm X 2.403mm X
0.600mm High
APPLICATIONS
• White LED Display Backlights
• White LED Keypad Backlights
• 1-Cell Li-Ion Battery-Operated Equipment Including PDAs, Hand-Held PCs, Cellular Phones
DESCRIPTION
The LM2794/95 is a fractional CMOS charge-pump that provides four regulated current sources. It accepts an input voltage range from 2.7V to 5.5V and maintains a constant current determined by an external sense resistor.
The LM2794/5 delivers up to 80mA of load current to accommodate four White LEDs. The switching frequency is 325kHz. (min.) to keep the conducted noise spectrum away from sensitive frequencies within portable RF devices.
Basic Application Circuit
CIN 1PF C1
C2
VIN POUT
C1+ 1PF
C1C2+ 1PF LM2794/95 C2SD
D1 D2 D3 D4
BRGT GND
ISET
CHOLD 1PF
LED1 LED2 LED3 LED4
RSET
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 © 2002–2013, Texas Instruments Incorporated
LM2794, LM2795
SNVS168L – JANUARY 2002 – REVISED MAY 2013
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DESCRIPTION (CONTINUED)
Brightness can be controlled by both linear and PWM techniques. A voltage between 0V and 3.0V may be applied to the BRGT pin to linearly vary the LED current. Alternatively, a PWM signal can be applied to the SD pin to vary the perceived brightness of the LED. The SD pin reduces the operating current to 2.3µA (typ.) The LM2794 is shut down when the SD pin is low, and the LM2795 is shut down when the SD pin is high.
The LM2794/95 is available in a DSBGA CSP package.
Connection Diagram
E7 D6
E5
C7
A7 B6
A5
E3 A3 D2 B2
E1 C1 A1
Figure 1. DSBGA Package Bottom View
Pin (1) A1 B2 C1 D2 E1
E3,E5,E7,D6 C7 B6 A7
A5 A3
Name C1+ C1− VIN GND C2− D1−4 ISET BRGT SD
C2+ POUT
PIN DESCRIPTION
Function Positive terminal of C1 Negative terminal of C1 Power supply voltage input Power supply ground input Negative terminal of C2 Current source outputs. Connect directly to LED Current Sense Input. Connect 1% resistor to ground to set constant current through LED Variable voltage input controls output current The LM2794 has an active-low shutdown pin (LOW = shutdown, HIGH = operating). The LM2795 has an active-high shutdown pin (HIGH = shutdown, LOW = operating) that has a pull-up to VIN. Positive terminal of C2 Charge pump output
(1) Note that the pin numbering scheme for the DSBGA package was revised in April, 2002 to conform to JEDEC standard. Only the pin numbers were revised. No changes to the physical location of the inputs/outputs were made. For reference purpose, the obsolete numbering had C1+ as pin 1, C1- as pin 2, VIN as pin 3, GND as pin 4, C2- as pin 5, D1-D4 as pin 6,7,8 & 9, Iset as pin 10, BRGT as pin 11, SD as pin 12, C2+ as pin 13, Pout as pin 14
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.
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Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2794 LM2795
LM2794, LM2795
www.ti.com
SNVS168L – JANUARY 2002 – REVISED MAY 2013
Absolute Maximum Ratings (1)(2)
VIN SD
BRGT Continuous Power Dissipation (3) TJMAX (3) θJA (3) (4) Storge Temperature
Lead Temp. (Soldering, 5 sec.) ESD Rating (5)
Human Body Model
Machine Model
−0.5 to 6.2V max −0.5 to (VIN+0.3V) w/ 6.2V max −0.5 to (VIN+0.3V) w/ 6.2V max
Internally Limited 135°C
125°C/W −65°C to +150°C
260°C
2kV 200V
(1) Absolute maximum ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when
operating the device beyond its rated operating conditions.
(2) Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and.