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參數資料
| 型號： | TL1454IDR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A DUAL SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | PLASTIC, SO-16 |
| 文件頁數： | 22/25頁 |
| 文件大小： | 412K |
| 代理商： | TL1454IDR |
TL1454, TL1454Y
DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM)
CONTROL CIRCUIT
SLVS086B – APRIL 1995 – REVISED NOVEMBER 1997
6
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
dead-time control (DTC) and soft start
The two PWM channels have independent dead-time control inputs so that the maximum power-switch duty
cycles can be limited to less then 100%. The dead-time is set with a voltage applied to DTC; the voltage is
typically obtained from a resistive divider connected between the reference and ground as shown in Figure 4.
Soft start is implemented by adding a capacitor between REF and DTC.
The voltage, VDT, required to limit the duty cycle to a maximum value is given by:
V
DT +
V
O(max) *
D V
O(max) *
V
O(min) *
0.65
where VO(max) and VO(min) are obtained from Figure 9, and D is the maximum duty cycle.
Predicting the regulator startup or rise time is complicated because it depends on many variables, including:
input voltage, output voltage, filter values, converter topology, and operating frequency. In general, the output
will be in regulation within two time constants of the soft-start circuit. A five-to-ten millisecond time constant
usually works well for low-power converters.
The DTC input can be grounded in applications where achieving a 100% duty cycle is desirable, such as a buck
converter with a very low input-to-output differential voltage. However, grounding DTC prevents the
implementation of soft start, and the output voltage overshoot at power-on is likely to be very large. A better
arrangement is to omit RDT1 (see Figure 4) and choose RDT2 = 47 k. This configuration ensures that the duty
cycle can reach 100% and still allows the designer to implement soft start using CSS.
CSS
REF
TL1454
RDT1
DTC
RDT2
16
Figure 4. Dead-Time Control and Soft Start
PWM comparator
Each of the PWM comparators has dual inverting inputs. One inverting input is connected to the output of the
error amplifier; the other inverting input is connected to the DTC terminal. Under normal operating conditions,
when either the error-amplifier output or the dead-time control voltage is higher than that for the PWM triangle
wave, the output stage is set inactive (OUT1 low and OUT2 high), turning the external power stage off.
undervoltage-lockout (UVLO) protection
The undervoltage-lockout circuit turns the output circuit off and resets the SCP latch whenever the supply
voltage drops too low (to approximately 2.9 V) for proper operation. A hysteresis voltage of 200 mV eliminates
false triggering on noise and chattering.
short-circuit protection (SCP)
The TL1454 SCP function prevents damage to the power switches when the converter output is shorted to
ground. In normal operation, SCP comparator 1 clamps SCP to approximately 185 mV. When one of the
converter outputs is shorted, the error amplifier output (COMP) will be driven below 1 V to maximize duty cycle
and force the converter output back up. When the error amplifier output drops below 1 V, SCP comparator 1
releases SCP, and capacitor, CSCP, which is connected between SCP and GND, begins charging. If the
error-amplifier output rises above 1 V before CSCP is charged to 1 V, SCP comparator 1 discharges CSCP and
normal operation resumes. If CSCP reaches 1 V, SCP comparator 2 turns on and sets the SCP latch, which turns
off the output drives and resets the soft-start circuit. The latch remains set until the supply voltage is lowered
to 2 V or less, or CSCP is discharged externally.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| TL1454IN | 制造商:TI 制造商全稱:Texas Instruments 功能描述:DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM) CONTROL CIRCUIT |
| TL1454N | 制造商:TI 制造商全稱:Texas Instruments 功能描述:DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM) CONTROL CIRCUIT |
| TL1454PW | 制造商:TI 制造商全稱:Texas Instruments 功能描述:DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM) CONTROL CIRCUIT |
| TL1454Y | 制造商:TI 制造商全稱:Texas Instruments 功能描述:DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM) CONTROL CIRCUIT |
| TL1454YD | 制造商:TI 制造商全稱:Texas Instruments 功能描述:DUAL-CHANNEL PULSE-WIDTH-MODULATION (PWM) CONTROL CIRCUIT |
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