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參數(shù)資料
| 型號： | PT7721A |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 17 A SWITCHING REGULATOR, 400 kHz SWITCHING FREQ-MAX, MSMA27 |
| 封裝： | SIP-27 |
| 文件頁數(shù)： | 6/8頁 |
| 文件大小： | 166K |
| 代理商： | PT7721A |
For technical support and more information, see inside back cover or visit www.ti.com
Application Notes continued
Using the Standby Function on the PT7720
“Big Hammer II” Programmable ISRs
For applications requiring output voltage On/Off control,
the PT7720 “Big Hammer” ISRs incorporate a standby
function. This feature may be used for power-up/shut-
down sequencing, and wherever there is a requirement
for the output status of the module to be controlled by
external circuitry.
The standby function is provided by the STBY* control,
pin 5. If pin 5 is left open-circuit the regulator operates
normally, providing a regulated output whenever a valid
supply voltage is applied to Vin (pins 7-11) with respect to
GND (pins 13-19). Connecting pin 5 to ground 1 will set
the regulator output to zero volts 2. This places the regu-
lator in standby mode, and reduces the input current to
typcially 30mA (50mA max). If a ground signal is applied
to pin 5 prior to power-up, the regulator output will be
held at zero volts during the period that input power is
applied.
The standby input must be controlled with an open-col-
lector (or open-drain) discrete transistor (See Figure 3-1).
Table 3-1 gives the threshold requirements.
Table 3-1 Inhibit Control Threshold 1
Parameter
Min
Max
Disable (VIL)
–0.1V
0.3V
Notes:
1. The Standby input on the PT7720 regulator series must be
controlled using an open-collector (or open-drain) discrete
transistor. Do Not use a pull-up resistor. The control input
has an open-circuit voltage of about 1.5Vdc. To set the
regulator output to zero, the control pin must be “pulled”
to less than 0.3Vdc with a low-level 0.1mA sink to ground.
2. When placed in the standby mode, the regulator output
discharges the output capacitance with a low impedance to
ground. If an external voltage is applied to the output, it
will sink current and possibly over-stress the part.
3. The turn-off time of Q1, or rise time of the standby input
is not critical on the PT7720 series. Turning Q1 off slowly,
over periods up to 100ms, will not affect regulator
operation. However, a slow turn-off time will increase
both the initial delay and rise-time of the output voltage.
Figure 3-1
Turn-On Time:
Turning Q1 in Figure 3-1 off, removes the
low-voltage signal at pin 5 and enables the output. Fol-
lowing a brief delay of 5-15ms, the output voltage of the
PT7720 series regulators rise to full regulation within
20ms3. Figure 3-2 shows the typical output voltage wave-
form of a PT7721, following the prompt turn-off of Q1 at
time t =0 secs. The output voltage in Figure 3-1 is set to
3.3V by connecting VID0 (pin 1), VID2 (pin 3), and
VID3 (pin 4) to the Sense Gnd (pin 12)*. The wave-
form in Figure 3-2 was measured with a 12-V input
source voltage, and 15-A resistive load.
Figure 3-2
C
out
+
C
in
+
+12V
COM
Inhibit
L
O
A
D
PT7721
64321
26
20-25
12
5
13-19
27
7-11
Vo
Vin
GND
Rem Sns (+)
Synch
Out
STBY
VID4 - VID0
Rem Sns (–)
V
o
=3.3V
COM
Q1
BSS138
* Consult the data sheet for details on other VID codes.
PT7720 Series
0
5
10
15
20
t (milli - secs)
Vo (2V/Div)
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| PT7721C | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PROGRAMMABLE ISR 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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| PT7721N | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 PROGRAMMABLE ISR 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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| PT7722 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:17 AMP 12V INPUT “BIG-HAMMER II” PROGRAMMABLE ISR |
| PT7722A | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 4.5-7.6Vout 17Amp 12 Vin Programmable ISR 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(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| PT7722C | 制造商:POWERTRENDS 功能描述: |
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