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PDF T6322A Data sheet ( Hoja de datos )
| Número de pieza | T6322A | |
| Descripción | PWM Control 1.5A Step-Down Converter | |
| Fabricantes | Taiwan Memory Technology | |
| Logotipo |  |
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tm TE
CH
FEATURES
• Wide Input Voltage Range: 7V to 30V
• LED Output Current Up to 1.5A
• Soft-start
• Single pin on/off and brightness control
using DC voltage or PWM
• High efficiency (up to 97%)
• Up to 1MHz switching frequency
• Typical 5% output current accuracy
• SOT-23 and SOP-8 Lead-free Package
Applications
• LED/Display Back Light Driver
• Lightings
• Portable Communication Devices
• Handheld Electronics
T6322A
PWM Control 1.5A Step-Down Converter
GENERAL DESCRIPTION
The T6322A 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 30V and
provides an externally adjustable output
current of up to 1.5A. Depending upon supply
voltage and external components, this can
provide up to 42 watts of output power. The
T6322A includes the output switch and a high-
side output current sensing circuit, which uses
an external resistor to set the nominal average
output current. Output current can be adjusted
above, or below the set value, by applying an
external control signal to the 'ADJ' pin. The
ADJ pin will accept either a DC voltage or a
PWM waveform. Depending upon the control
frequency, this will provide either a continuous
or a gated output current. The PWM filter
components are contained within the chip. The
T6322A is available in SOT-23 and SOP-8
Lead-free package.
PART NUMBER EXAMPLES
PART NO.
T6322A-AXG
T6322A-ADG
PACKAGE
SOT-23
SOP-8
TM Technology Inc. reserves the right
P. 1
to change products or specifications without notice.
Publication Date: NOV. 2008
Revision: A
1 page  
tm TE
CH
T6322A
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 ADJ pin of the device is unconnected and
the voltage on this pin (VADJ) 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 (VADJ), 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 15% of VADJ.
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 to VADJ, the comparator output
switches high again. This cycle of events repeats, with the comparator input ramping between limits
of VADJ ± 15%.
Switching thresholds
With VADJ = VREF, the ratios of R1, R2 and R3 define an average VSENSE switching threshold of
100mV (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 = 100mV/RS
Nominal ripple current is ±15mV/RS
Adjusting output current
The device contains a low pass filter between the ADJ pin and the threshold comparator and an
internal current limiting resistor (200kohn nom) between ADJ and the internal reference voltage.
This allows the ADJ pin to be overdriven with either DC or pulse signals to change the VSENSE
switching threshold and adjust the output current. The filter is third order, comprising three sections,
each with a cut-off frequency of nominally 4kHz. Details of the different modes of adjusting output
current are given in the applications section.
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: NOV. 2008
Revision: A
5 Page 
tm TE
CH
PACKAGE DIMENSIONS
8-LEAD SOP
B
B1
K
T h e rm a l P a d * J A 1 A
T6322A
C1 C
C2
DH
F
E
Symbol
A
A1
B
B1
C
C1
C2
D
E
F
J
K
H
Min.
5.70
3.75
-
-
-
1.35
0.10
0.31
0.30
0.10
Dimension in mm
Typ. Max.
6.00 6.30
3.95 4.10
- 5.13
1.27 -
- 1.80
1.55 1.75
- 0.25
0.41 0.51
0.50 0.70
0.15 0.25
2.23 REF
2.97 REF
0~8°
Dimension in inch
Min.
Typ. Max.
0.224
0.236
0.248
0.148
0.156
0.164
- - 0.202
- 0.050 -
- - 0.071
0.052
0.061
0.069
0.001 - 0.004
0.012
0.016
0.020
0.012
0.020
0.028
0.004
0.006
0.010
0.088 REF
0.117 REF
0~8°
*Note :
The thermal pad on the IC’s bottom has to be mounted on the copper foil.
To eliminate the noise influence, the thermal pad is suggested to be connected to GND on PCB.
In addition, desired thermal conductivity will be improved, if a heat-conducting copper foil on
PCB is soldered with thermal pad. The thermal pad enhances the power dissipation. As a result, a
large amount of current can be sunk safely in one package.
TM Technology Inc. reserves the right
P. 11
to change products or specifications without notice.
Publication Date: NOV. 2008
Revision: A
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet T6322A.PDF ] | |
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