TK11850LTL TOKO [TOKO, Inc], TK11850LTL Datasheet

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TK11850LTL

Manufacturer Part Number
TK11850LTL
Description
WHITE LED DRIVER
Manufacturer
TOKO [TOKO, Inc]
Datasheet
1.TK11850LTL.pdf (14 pages)

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Company:
Meier Automation Equipment Co., Limited Meier Automation Equipment Co., Limited
Part Number:
TK11850LTL-G
Manufacturer:
TOKO
Quantity:
20 000
May 2001 TOKO, Inc.
FEATURES
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DESCRIPTION
The TK11850L is a pulse skipping step-up DC-DC converter
IC designed for White LED driver applications with the
following built in: a very high current switching transistor
(400 mA peak), an inductor current limit detector, low
voltage reference (Vref = 0.5 V), high speed oscillator, an
error comparator, a rectifier diode (for small power output)
and an ON/OFF control. The IC works with a very wide
operating supply range (2.3 V to 10 V) and the adjustable
output voltage can be set as high as 20 V. The device is in
the ON state when the EN pin is pulled to a high level. Using
the very small TK11850L and a few external components,
battery powered systems with LCD displays such as digital
cameras and cellular phones can be effectively backlit with
white LEDs. The white LEDs are connected in series and
driven at a constant current resulting in uniform brightness
and high efficiency. This IC has an oscillator, which allows
the designer to set the operating frequency by an external
capacitor with the output controlled by pulse skipping. The
reference voltage is a very low 0.5 V, achieving high
efficiency operation with the constant current output. A
small coil can be used because the inductor current limit
detector circuit limits the peak current (caused by an input
Very High Speed Adjustable OSC (Max 800 kHz)
Very Wide Operating Voltage Range (2.3 V to 10 V)
Low Loss Detector (Low Reference Voltage:
V
Operates with Toko D31FU Miniature Coil (Current
Limited by Input Current Sensor)
Internal Switching Transistor
Internal Diode
Active High On / Off Control
Available Intensity Control Using EN Pin with PWM
Signal
Very Small SOT23L-8 Surface Mount Package
REF
= 0.5 V)
ORDERING INFORMATION
TK11850L
Tape/Reel Code
TAPE/REEL CODE
TL: Tape Left
APPLICATIONS
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voltage increase or the inrush current as start-up) that flows
through the coil. The ON /OFF control is built-in and the
circuit current can be decreased when the EN pin is low
(standby mode). The white LEDs can be dimmed by
applying a PWM signal to the EN (ON/OFF control) pin. With
this method, the white LED brightness is still controlled by
constant current resulting in constant chromaticity.
The TK11850L is available in the SOT23L-8 surface mount
package.
LED Backlighting and Frontlighting
LED Flashlights
Step-up DC-DC Converters
V OUT
EXT
V IN
I S
0.1 V
+
-
I S COMP
BLOCK DIAGRAM
TK11850
Q
WHITE LED DRIVER
S
R
C X
CLK
V OUT
0.86 V
EXT
V IN
0.3 V
I S
OSC
BAND GAP REFERENCE
TK11850L
CLK
0.525 V
V REF
ERROR
COMP
+
-
8
7
EN
C X
GND
V FB
Page 1
7 C X
8 EN
GND
V FB

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TK11850LTL Summary of contents

Page 1

FEATURES n Very High Speed Adjustable OSC (Max 800 kHz) n Very Wide Operating Voltage Range (2 Low Loss Detector (Low Reference Voltage 0.5 V) REF n Operates with Toko D31FU Miniature Coil ...

Page 2

TK11850L ABSOLUTE MAXIMUM RATINGS Supply Voltage ........................................................ 20 V Switching Voltage .................................................... 20 V Operating Voltage Range ............................... 2 Power Dissipation (Note 1) ................................. 400 mW Storage Temperature Range ..................... -55 to +150 °C TK11850 ELECTRICAL CHARACTERISTICS ...

Page 3

TK11850 ELECTRICAL CHARACTERISTICS (CONT) Test Conditions ...

Page 4

TK11850L EXT V EXT V I VOUT V VOUT 3.6 V Page 4 TEST CIRCUIT ...

Page 5

TYPICAL PERFORMANCE CHARACTERISTICS OSC PERIOD vs CAPACITANCE 100 200 C X ...

Page 6

TK11850L TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) SUPPLY CURRENT vs. EN INPUT BIAS CURRENT 100 pF 3 ...

Page 7

APPLICATION CIRCUIT (2 LEDs in Series) • Input Voltage: 2.7 V • LED Current : 20 mA • On/Off: Pin Number 8 (EN Pin) LED Current ( set by R LED I doesn’t depend on V LED is ...

Page 8

TK11850L APPLICATION CIRCUIT (3 LEDs in Series) • Input Voltage: 2.7 V • LED Current • On/Off: Pin Number 8 (EN Pin) LED Current ( set by R LED I doesn’t depend on V LED is ...

Page 9

APPLICATION CIRCUIT (4 LEDs in Series) • Input Voltage: 2.7 V • LED Current • On/Off: Pin Number 8 (EN Pin) LED Current ( set by R LED I doesn’t depend on V LED is controlled ...

Page 10

TK11850L The following are 3 kinds of dimming methods. 1. Dimming by R LED The current of the LED ( determined by R LED Example of 3 LEDs with a 4 brightness level circuit: 0 ...

Page 11

PWM Dimming Apply the PWM signal to the EN Terminal (Pin no. 8). In this case, a signal frequency of approximately120 Hz is adequate. The average current of the LED changes due to the On/Off cycle of the IC, ...

Page 12

TK11850L Input PWM signal curve vs. LED current curve (ex. Three LEDs, Output current 20 mA) (1) Duty Cycle = 80% (2) Duty Cycle = 50% (3) Duty Cycle = 20% Page 12 LED CURRENT 2.0 mSec/Div PWM SIGNAL (Applied ...

Page 13

Dimming by DAC (D/A Converter) output Dimming is achievable by applying a DAC output to the GND OUT Example Conditions DAC1 DAC2 = ...

Page 14

TK11850L SOT23L Marking 1 4 +0.15 e 0.8 0.3 - 0.05 +0.3 - 0.1 3.5 (3.4) 0.1 Dimensions are shown in millimeters Tolerance: x.x = ± 0.2 mm (unless otherwise specified) TOKO AMERICA REGIONAL OFFICES Midwest Regional Office ...

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