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參數(shù)資料
| 型號(hào)： | TC125 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | PFM Step-Up DC/DC Regulators |
| 中文描述： | PFM步升直流/直流穩(wěn)壓器 |
| 文件頁(yè)數(shù)： | 4/12頁(yè) |
| 文件大?。?/td> | 459K |
| 代理商： | TC125 |
TC125/TC126
DS21372B-page 4
2002 Microchip Technology Inc.
3.0
DETAILED DESCRIPTION
The TC125/126 are PFM step-up DC/DC regulators for
use in systems operating from two or more cells or in
low voltage, line powered applications. Because Pulse
Frequency Modulation (PFM) is used, the TC125/126
switching frequency (and therefore supply current) is
minimized at low output loads. This is especially
important in battery operated applications (such as
pagers) that operate in standby mode most of the time.
For example, a TC125/126 with a 3V output and no
load will consume a maximum supply current of only
10
μ
A versus a supply current of 40
μ
A maximum when
I
OUT
= 30mA. Both devices require only an external
inductor, diode and capacitor to implement a complete
DC/DC converter.
The TC125 is recommended for applications requiring
shutdown mode as a means of reducing system supply
current. The TC125 is powered from the PS input,
which must be connected to the regulated output as
shown in Figure 3-1. PS also senses output voltage for
closed-loop regulation. Start-up current is furnished
through the inductor when input voltage is initially
applied. This action starts the oscillator, causing the
voltage at the PS input to rise, bootstrapping the
regulator into full operation.
The TC126 (Figure 3-2) is recommended for all appli-
cations not requiring shutdown mode. It has separate
V
DD
and SENSE inputs, allowing it to be powered from
any source of 2.2V to 10V in the system. The V
DD
input
of the TC126 may be connected to the V
IN
, V
OUT
, or an
external DC voltage. Lower values of V
DD
result in
lower supply current, but lower efficiency due to higher
switch ON resistance. Higher V
DD
values increase
supply
current,
but
drive
transistor harder (lowering RDS
ON
), thereby increasing
efficiency.
the
internal
switching
3.1
Low Power Shutdown Mode
The TC125 enters a low power shutdown mode when
SHDN is brought low. While in shutdown, the oscillator
is disabled and the internal switch is shut off. Normal
regulator operation resumes when SHDN is brought
high. Because the TC125 uses an external diode, a
leakage path between the input voltage and the output
node (through the inductor and diode) exists while the
regulator is in shutdown. Care must be taken in system
design to assure the input supply is isolated from the
load during shutdown.
3.2
Behavior When V
IN
is Greater
Than the Factory-Programmed
OUT Setting
The TC125 and TC126 are designed to operate as
step-up regulators only. As such, V
IN
is assumed to
always be less than the factory-programmed output
voltage setting (V
R
). Operating the TC125/126 with
V
IN
> V
R
causes regulating action to be suspended
(and corresponding supply current reduction) until V
IN
is again less than V
R
. While regulating action is
suspended, V
IN
is connected to the output voltage node
through the series combination of the inductor and
Schottky diode. Again, care must be taken to add the
appropriate isolation (MOSFET series switch or post
LDO with shutdown) during system design if this V
IN
/
V
OUT
leakage path is problematic.
FIGURE 3-1:
TYPICAL TC125 CIRCUIT
FIGURE 3-2:
TYPICAL TC126 CIRCUIT
L1
100
μ
H Sumida CD54
D1
MA735
Shutdown
Control
1
2
3
5
4
TC125
LX
SHDN
NC
PS
GND
1.5V
ON
OFF
V
3.3V @40mA
C
1
47
μ
F/16V
Tantalum
+
1
2
3
4
5
TC126
LX
SENSE
NC
V
DD
GND
3.3V
Line
Supply
L1
100
μ
H Sumida CD54
D1
MA735
V
5V @80mA
C
1
47
TanF/16V
+
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TC-125.000MBD-T | 功能描述:標(biāo)準(zhǔn)時(shí)鐘振蕩器 125.000MHz 3.3V 25ppm -40C to 85C RoHS:否 制造商:AVX 產(chǎn)品:Standard Clock Oscillators 封裝 / 箱體:7 mm x 5 mm 頻率:75 MHz 頻率穩(wěn)定性:50 PPM 電源電壓:2.5 V 負(fù)載電容: 端接類型:SMD/SMT 最小工作溫度:0 C 最大工作溫度:+ 70 C 輸出格式:LVDS 尺寸: 封裝:Reel 系列: |
| TC-125.000MBE-T | 制造商:TXC Corporation 功能描述:OSC MEMS 125.000 MHZ 3.3V SMD |
| TC-125.000MCD-T | 功能描述:標(biāo)準(zhǔn)時(shí)鐘振蕩器 125.000MHz 2.5V 25ppm -40C to 85C RoHS:否 制造商:AVX 產(chǎn)品:Standard Clock Oscillators 封裝 / 箱體:7 mm x 5 mm 頻率:75 MHz 頻率穩(wěn)定性:50 PPM 電源電壓:2.5 V 負(fù)載電容: 端接類型:SMD/SMT 最小工作溫度:0 C 最大工作溫度:+ 70 C 輸出格式:LVDS 尺寸: 封裝:Reel 系列: |
| TC-125.000MCE-T | 制造商:TXC Corporation 功能描述:OSC MEMS 125.000 MHZ 2.5V SMD |
| TC125301ECT | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:PFM Step-Up DC/DC Regulators |
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