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PDF TK11900M Data sheet ( Hoja de datos )
| Número de pieza | TK11900M | |
| Descripción | ADJUSTABLE LOW DROPOUT REGULATOR | |
| Fabricantes | TOKO | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de TK11900M (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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TK11850L
WHITE LED DRIVER
FEATURES
n Very High Speed Adjustable OSC (Max 800 kHz)
n Very Wide Operating Voltage Range (2.3 V to 10 V)
n Low Loss Detector (Low Reference Voltage:
VREF = 0.5 V)
n Operates with Toko D31FU Miniature Coil (Current
Limited by Input Current Sensor)
n Internal Switching Transistor
n Internal Diode
n Active High On / Off Control
n Available Intensity Control Using EN Pin with PWM
Signal
n Very Small SOT23L-8 Surface Mount Package
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
ORDERING INFORMATION
TK11850L
Tape/Reel Code
TAPE/REEL CODE
TL: Tape Left
APPLICATIONS
n LED Backlighting and Frontlighting
n LED Flashlights
n Step-up DC-DC Converters
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.
TK11850
VIN
IS
EXT
VOUT
8 EN
7 CX
GND
VFB
BLOCK DIAGRAM
0.1 V
IS COMP
VIN +
-
IS
BAND GAP REFERENCE
OSC
0.86 V
CX 0.3 V
CLK
CLK
8 EN
7 CX
EXT
VOUT
S
QR
ERROR
COMP
+
-
VREF
0.525 V
GND
VFB
May 2001 TOKO, Inc.
Page 1
1 page  
TK11850L
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25 °C, unless otherwise specified.
OSC PERIOD vs. CX
CAPACITANCE
12
11
10 VIN = 3 V
9 VIS = VEN = VIN
8
OSC FREQUENCY vs.
TEMPERATURE
300
280
VIN = 3 V
VIN = 5 V
VIN = 10 V
260
7
6 240
5
4 220
3 VIS = VEN =VIN
2 200 CX = 100 pF
1
0 180
0 100 200 300 -30 -10 10 30 50 70 90
CX CAPACITANCE (pF)
TEMPERATURE (°C)
MAXIMUM DUTY CYCLE vs.
OSC FREQUENCY
80
VIN = 3 V
VIS = VEN = VIN
VFB = 0 V
75
70
65
10
100 1000
OSC FREQUENCY (kHz)
SWITCHING CURRENT vs.
SWITCH SATURATION VOLTAGE
500
400
300
-20 °C
25 °C
85 °C
200
100
VIN = 3 V
VIS = VEN = VIN
VFB = 0 V
VCX = 0 V
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
SWITCH SATURATION
VOLTAGE (V)
REFERENCE VOLTAGE vs.
SUPPLY VOLTAGE
530
528
526
524
VIS = VEN = VIN
522
520
518
516
0
24
68
SUPPLY VOLTAGE (V)
10
INDUCTOR CURRENT-LIMIT SENSE
VOLTAGE vs. SUPPLY VOLTAGE
100
90 -20 °C
80 25 °C
85 °C
70
60 Vlimit = VIS - VIN
50 VEN = VIN
40
30
20
10
0
2 4 6 8 10 12
SUPPLY VOLTAGE (V)
IS INPUT BIAS CURRENT
vs. IS VOLTAGE
100
90
-20 °C
25 °C
80 85 °C
70
60
50
40
30
20 VIN = VEN = VIS
10 VFB = 1 V
0
0 2 4 6 8 10 12 14 16 18 20
IS VOLTAGE (V)
REFERENCE VOLTAGE vs.
TEMPERATURE
530
528
526
VIN = 3 V
VIS = VEN = VIN
524
522
520
518
516
-30 -10 10 30 50 70
TEMPERATURE (°C)
90
SUPPLY CURRENT vs.
EN VOLTAGE
10
-20 °C
9 25 °C
8 85 °C
7
6
5
VIN = 3 V
4 VIS = VIN
3 VFB = 0 V
CX = 100 pF
2
1
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
EN VOLTAGE (V)
May 2001 TOKO, Inc.
Page 5
5 Page 
TK11850L
DIMMING (CONT)
2. 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, which follows the duty cycle of the PWM signal.
Set the PWM signal at a high level over 2 V and a low level under 0.6 V, with a driving current over 2 mA.
VIN
CIN
GND
RSC
VIN 0.1 V
IS COMP
+
-
IS
L
EXT
CLK
BAND GAP REFERENCE
OSC
0.86 V
Cx 0.3 V
CLK
CLK
EN
8
ON/OFF
CX
7
GND
CX
LED CURRENT CURVE vs. PWM SIGNAL CURVE
LED SETTING
CURRENT
LED CURRENT
D
VOUT
S
QR
ERROR
COMP
+
-
VREF
0.525 V
VFB
Ton Toff
PWM SIGNAL
(Applied to On/Off pin.)
2.0 V
0.6 V
COUT
fdim = 1 / T = 120 Hz
Duty (%) = (Ton * 100) / T
T
VLED
ILED
(LED CURRENT)
RLED
The PWM dimming LED current follows the PWM signal. (As shown above)
The average LED current is obtained from the formula below. The graph below shows an example with ILED(MAX) (20 mA) at
a Duty Cycle up to 100%.
ILED vs. DUTY
I = I * Duty
LED(AVG)
LED(MAX) 100
DUTY (%)
ILED (mA)
100 20.0
90 18.0
80 16.0
70 14.0
60 12.0
50 10.0
40 8.0
30 6.0
20 4.0
10 2.0
LED CURRENT (ILED) vs.
DUTY CYCLE OF INPUT PWM SIGNAL
20
18
16
14
12
10
8
6
4
2
0
0
20 40
60 80 100
DUTY CYCLE (%)
May 2001 TOKO, Inc.
Page 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet TK11900M.PDF ] | |
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