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參數(shù)資料
| 型號(hào)： | ISL6430 |
| 廠商： | Intersil Corporation |
| 英文描述： | Single Sync Buck PWM Controller for Broadband Gateway Applications |
| 中文描述： | 單同步降壓PWM控制器，寬帶網(wǎng)關(guān)應(yīng)用 |
| 文件頁(yè)數(shù)： | 8/12頁(yè) |
| 文件大?。?/td> | 400K |
| 代理商： | ISL6430 |
5
Functional Description
Initialization
The ISL6430 automatically initializes upon receipt of power.
Special sequencing of the input supplies is not necessary.
The Power-On Reset (POR) function continually monitors
the input supply voltages and the enable (EN) pin. The POR
monitors the bias voltage at the VCC pin and the input
voltage (VIN) on the OCSET pin. The level on OCSET is
equal to VIN Less a fixed voltage drop (see over-current
protection). With the EN pin held to VCC, the POR function
initiates soft start operation after both input supply voltages
exceed their POR thresholds. For operation with a single
+12V power source, VIN and VCC are equivalent and the
+12V power source must exceed the rising VCC threshold
before POR initiates operation.
The Power-On Reset (POR) function inhibits operation with
the chip disabled (EN pin low). With both input supplies
above their POR thresholds, transitioning the EN pin high
initiates a soft start interval.
Soft Start
The POR function initiates the soft start sequence. An internal
10
A current source charges an external capacitor (C
SS) on
the SS pin to 4V. Soft start clamps the error amplifier output
(COMP pin) and reference input (+ terminal of error amp) to
the SS pin voltage. Figure 3 shows the soft start interval with
CSS = 0.1F.
Initially the clamp on the error amplifier (COMP pin) controls
the converter’s output voltage. At t1 in Figure 3, the SS
voltage reaches the valley of the oscillator’s triangle wave.
The oscillator’s triangular waveform is compared to the
ramping error amplifier voltage. This generates PHASE
pulses of increasing width that charge the output capacitor(s).
This interval of increasing pulse width continues to t2. With
sufficient output voltage, the clamp on the reference input
controls the output voltage. This is the interval between t2 and
t3 in Figure 3. At t3 the SS voltage exceeds the reference
voltage and the output voltage is in regulation. This method
provides a rapid and controlled output voltage rise.
Over-Current Protection
The over-current function protects the converter from a
shorted output by using the upper MOSFETs on-resistance,
rDS(ON) to monitor the current. This method enhances the
converter’s efficiency and reduces cost by eliminating a
current sensing resistor.
The over-current function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (ROCSET)
programs the over-current trip level. An internal 200
A
(typical) current sink develops a voltage across ROCSET that
is reference to VIN. When the voltage across the upper
MOSFET (also referenced to VIN) exceeds the voltage
across ROCSET, the over-current function initiates a soft-
start sequence. The soft-start function discharges CSS with
a 10
A current sink and inhibits PWM operation. The soft-
start function recharges CSS, and PWM operation resumes
with the error amplifier clamped to the SS voltage. Should an
overload occur while recharging CSS, the soft start function
inhibits PWM operation while fully charging CSS to 4V to
complete its cycle. Figure 4 shows this operation with an
overload condition. Note that the inductor current increases
to over 15A during the CSS charging interval and causes an
over-current trip. The converter dissipates very little power
with this method. The measured input power for the
conditions of Figure 4 is 2.5W.
The over-current function will trip at a peak inductor current
(IPEAK) determined by:
where IOCSET is the internal OCSET current source (200A
- typical). The OC trip point varies mainly due to the
MOSFETs rDS(ON) variations. To avoid over-current tripping
TIME (5ms/DIV)
SOFT-START
(1V/DIV)
0V
t1
t2
t3
OUTPUT
(1V/DIV)
VOLTAGE
FIGURE 3. SOFT-START INTERVAL
OUTPUT
INDUCT
OR
SOFT
-S
TART
0A
0V
TIME (20ms/DIV)
5A
10A
15A
2V
4V
FIGURE 4. OVER-CURRENT OPERATION
I
PEAK
I
OCSET
R
OCSET
r
DS ON
()
---------------------------------------------------
=
ISL6430
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| ISL6431CB | 功能描述:電壓模式 PWM 控制器 For Home Gateways RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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