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參數資料
| 型號： | FAN5236QSC |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩壓器 |
| 英文描述： | Dual Mobile-Friendly DDR / Dual-output PWM Controller |
| 中文描述： | DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | QSOP-28 |
| 文件頁數： | 11/20頁 |
| 文件大小： | 199K |
| 代理商： | FAN5236QSC |
FAN5236
PRODUCT SPECIFICATION
REV. 1.1.7 4/4/03
11
Hysteretic Mode
Conversely, the transition from Hysteretic mode to PWM
mode occurs when the SW node is negative for 8 consecutive
cycles.
A sudden increase in the output current will also cause a
change from hysteretic to PWM mode. This load increase
causes an instantaneous decrease in the output voltage due to
the voltage drop on the output capacitor ESR. If the load
causes the output voltage (as presented at VSNS) to drop
below the hysteretic regulation level (20mV below VREF),
the mode is changed to PWM on the next clock cycle.
In hysteretic mode, the PWM comparator and the error
amplifier that provide control in PWM mode are inhibited
and the hysteretic comparator is activated. In hysteretic
mode the low side MOSFET is operated as a synchronous
rectifier, where the voltage across ( V
DS(ON)
) it is monitored,
and it is switched off when V
DS(ON)
goes positive (current
flowing back from the load) allowing the diode to block
reverse conduction.
The hysteretic comparator initiates a PFM signal to turn on
HDRV at the rising edge of the next oscillator clock, when
the output voltage (at VSNS) falls below the lower threshold
(10mV below VREF) and terminates the PFM signal when
VSNS rises over the higher threshold (5mV above VREF).
The switching frequency is primarily a function of:
1.
Spread between the two hysteretic thresholds
2.
I
LOAD
Output Inductor and Capacitor ESR
3.
A transition back to PWM (Continuous Conduction Mode or
CCM) mode occurs when the inductor current rises suffi-
ciently to stay positive for 8 consecutive cycles. This occurs
when:
where
V
HYSTERESIS
= 15mV and ESR is the equivalent
series resistance of C
OUT
.
Because of the different control mechanisms, the value of the
load current where transition into CCM operation takes place
is typically higher compared to the load level at which transi-
tion into hysteretic mode occurs. Hysteretic mode can be
disabled by setting the FPWM pin low.
I
LOAD CCM
)
V
2 ESR
---------------------------------------
=
(3)
Figure 11. Current Limit / Summing Circuits
LDRV
PGND
ISNS
in +
in
2.5V
ILIM det.
R
SENSE
SS
1.5M
C
SS
VSEN
V to I
Reference and
Soft Start
17pf
I1B =
ISNS
9
I2 =
4 * ILIM
3
ILIM
0.9V
R
ILIM
ILIM mirror
S/H
TO PWM COMP
4.14K
300K
I1A =
ISNS
0.17pf
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| FAN5236QSCX | Dual Mobile-Friendly DDR / Dual-output PWM Controller |
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| FAN5240 | Multi-Phase PWM Controller for AMD Mobile Athlon TM and Duron TM |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| FAN5236QSC_Q | 功能描述:開關變換器、穩壓器與控制器 DC/DC RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| FAN5236QSCX | 功能描述:開關變換器、穩壓器與控制器 PWM Controller RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| FAN5240 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Multi-Phase PWM Controller for AMD Mobile Athlon TM and Duron TM |
| FAN5240_06 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Multi-Phase PWM Controller for AMD Mobile Athlon and Duron |
| FAN5240_ADC3116B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
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