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參數(shù)資料
| 型號： | TC2574-VOETR |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | WIDE, SOIC-16 |
| 文件頁數(shù)： | 8/25頁 |
| 文件大?。?/td> | 212K |
| 代理商： | TC2574-VOETR |
TC2574
16
TC2574-1 1/6/00
0.5A Step-Down Switching Regulator
ADDITIONAL APPLICATIONS
Inverting Regulator
An inverting buck–boost regulator using the TC2574
(12V) shown in Figure 8. This circuit converts a positive
input voltage to a negative output voltage with a common
ground by bootstrapping the regulators ground to the nega-
tive output voltage. By grounding the feedback pin, the
regulator senses the inverted output voltage and regulates
it.
In this example the TC2574 (12V) is used to generate a
–12V output. The maximum input voltage in this case cannot
exceed 28V because the maximum voltage appearing
across the regulator is the absolute sum of the input and
output voltages and this must be limited to a maximum of
40V.
This circuit configuration is able to deliver approximately
0.1 A to the output when the input voltage is 8.0 V or higher.
At lighter loads the minimum input voltage required drops to
approximately 4.7V, because the buck–boost regulator to-
pology can produce an output voltage that, in its absolute
value, is either greater or less than the input voltage.
Since the switch currents in this buck–boost configura-
tion are higher than in the standard buck converter topology,
the available output current is lower.
This type of buck–boost inverting regulator can also
require a larger amount of startup input current, even for light
loads. This may overload an input power source with a
current limit less than 0.6A.
Because of the relatively high startup currents required
by this inverting regulator topology, the use of a delayed
startup or an undervoltage lockout circuit is recommended.
While using a delayed startup arrangement, the input
capacitor can charge up to a higher voltage before the
switch–mode regulator begins to operate.
The high input current needed for startup is now partially
supplied by the input capacitor CIN.
Design Recommendations:
The inverting regulator operates in a different manner
than the buck converter and so a different design procedure
has to be used to select the inductor L1 or the output
capacitor COUT.
The output capacitor values must be larger than what is
normally required for buck converter designs. Low input
voltages or high output currents require a large value output
capacitor (in the range of thousands of
F).
The recommended range of inductor values for the
inverting converter design is between 68
H and 220 H. To
select an inductor with an appropriate current rating, the
inductor peak current has to be calculated.
The following formula is used to obtain the peak inductor
current:
IPEAK ≈
ILOAD (VIN – IVOUTI)
+
VIN x tON
VIN
2L1
where tON ≈
IVOUTI
1.0
, and fOSC = 52kHz.
VIN + IVOUTI
fOSC
Under normal continuous inductor current operating
conditions, the worst case occurs when VIN is minimal.
It has been already mentioned above, that in some
situations, the delayed startup or the undervoltage lockout
features could be very useful. A delayed startup circuit
applied to a buck–boost converter is shown in Figure 9.
Figure 15 in the “Undervoltage Lockout” section
describes an undervoltage lockout feature for the same
converter topology.
With the inverting configuration, the use of the ON/OFF
pin requires some level shifting techniques. This is caused
by the fact, that the ground pin of the converter IC is no
longer at ground. Now, the ON/OFF pin threshold voltage
(1.3V approximately) has to be related to the negative output
voltage level. There are many different possible shutdown
methods, two of them are shown in Figures 10 and 11.
Figure 9. Inverting Buck-Boost Regulator with Delayed Startup
D1
MBR150
L1
68
H
Output
7
1
Feedback
12 to 25V
Unregulated
DC Input
CIN
22mF
/50 V
5
4
3ON/OFF
Pwr
GND
+VIN
–12V @ 100mA
Regulated
Output
COUT
680
F
/16V
TC2574
(12V)
C1
0.1
F
R1
47k
R2
47k
2
Sig
GND
Figure 10. Inverting Buck-Boost Regulator Shutdown Circuit
Using an Optocoupler
TC2574–XX
5
2
and
4
3
GNDs
Pins
ON/OFF
+VIN
R2
47 k
CIN
22
F
NOTE: This picture does not show the complete circuit.
R1
47 k
R3
470
Shutdown
Input
MOC8101
–VOUT
Off
On
5.0 V
0
+VIN
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| TC2574VPA | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| TC2574-VPA | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:0.5A Step-Down Switching Regulator |
| TC2575 | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:1.0A Step-Down Switching Regulator |
| TC2575-12.0VAT | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:1.0A Step-Down Switching Regulator |
| TC2575-3.3VAT | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:1.0A Step-Down Switching Regulator |
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