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PDF T8306 Data sheet ( Hoja de datos )
| Número de pieza | T8306 | |
| Descripción | PWM Control 36V Step-Down Controller | |
| Fabricantes | TM Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de T8306 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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tm TE
CH
Features
• Wide Input Voltage Range: 7V to 36V
• LED Output Current Up to 3A
• With External Power MOSFET
• Soft-start
• Single pin on/off and brightness control
• High efficiency (up to 95%)
• Up to 1MHz switching frequency
• Typical 5% output current accuracy
• SOT-23 Lead-free Package
Applications
• CCTV IR LED Driver
• Lightings
• Portable Communication Devices
• Handheld Electronics
Preliminary T8306
PWM Control 36V Step-Down Controller
General Description
The T8306 is a continuous mode inductive
step-down converter, designed for driving
single or multiple series connected LEDs
efficiently from a voltage source higher than
the LED voltage. The device operates from an
input supply between 7V and 36V and provides
an externally adjustable output current of up to
3A. Depending upon supply voltage and
external components, The T8306 includes the
output switch and a high-side output current
sensing circuit, which uses an external resistor
to set the nominal average output current. The
T8306 is available in SOT23 Lead-free package.
Part Number Examples
PART NO.
T8306AX
PACKAGE
SOT23
TM Technology, Inc. reserves the right
P. 1
to change products or specifications without notice.
Publication Date: May. 2013
Revision:A
1 page  
tm TE
CH
T8306
Functional Description
The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a selfoscillating
continuous-mode buck converter.
Device operation
Operation can be best understood by assuming that the Vref of the device is unconnected and the
voltage on pin appears directly at the (+) input of the comparator.
When input voltage VIN is first applied, the initial current in L1 and RS is zero and there is no
output from the current sense circuit. Under this condition, the (-) input to the comparator is at
ground and its output is high. This turns MN on and switches the LX pin low, causing current to
flow from VIN to ground, via RS, L1 and the LED(s). The current rises at a rate determined by VIN
and L1 to produce a voltage ramp (VSENSE) across RS. The supply referred voltage VSENSE is
forced across internal resistor R1 by the current sense circuit and produces a proportional current in
internal resistors R2 and R3. This produces a ground referred rising voltage at the (-) input of the
comparator. When this reaches the threshold voltage, the comparator output switches low and MN
turns off. The comparator output also drives another NMOS switch, which bypasses internal resistor
R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 20% .
When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to VIN. The
current decays at a rate determined by the LED(s) and diode forward voltages to produce a falling
voltage at the input of the comparator. When this voltage returns , the comparator output switches
high again. This cycle of events repeats, with the comparator input ramping between limits of ±
20%.
Switching thresholds
With VREF the ratios of R1, R2 and R3 define an average VSENSE switching threshold of 200mV
(measured on the ISENSE pin with respect to VIN). The average output current IOUTnom is then
defined by this voltage and RS according to:
IOUTnom = 200mV/RS
Output shutdown
The output of the low pass filter drives the shutdown circuit. When the input voltage to this circuit
falls below the threshold, the internal regulator and the output switch are turned off. The voltage
reference remains powered during shutdown to provide the bias current for the shutdown circuit.
Quiescent supply current during shutdown is nominally 35uA and switch leakage is below 5uA.
TM Technology, Inc. reserves the right
P. 5
to change products or specifications without notice.
Publication Date: May. 2013
Revision: A
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet T8306.PDF ] | |
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