參數(shù)資料
型號： MC34701EK
廠商： 飛思卡爾半導(dǎo)體(中國)有限公司
英文描述： 1.5 A Switch-Mode Power Supply with Linear Regulator
中文描述： 1.5開關(guān)模式電源，線性穩(wěn)壓器
文件頁數(shù)： 19/38頁
文件大小： 739K
代理商： MC34701EK
Analog Integrated Circuit Device Data
Freescale Semiconductor
19
34701
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Figure 15. LDO Converter Overcurrent Protection
The output voltage VOUT can be adjusted by means of an
external resistor divider connected to the feedback control
terminal INV. The switching regulator output voltage can be
adjusted in the range of 0.8 V to V
IN
- buck dropout voltage.
Power-up, power-down, and fault management are
coordinated with the linear regulator.
SWITCHER OSCILLATOR
A 300 kHz (default) oscillator sets the switching frequency
of the buck regulator. The frequency of the oscillator can be
adjusted between 200 kHz and 400 kHz by an optional
external resistor R
F
connected from the FREQ terminal of the
integrated circuit to ground. See
Figure 6
on page 14 for
frequency resistor selection.
The CLKSYN terminal can be configured as either an
oscillator output when the CLKSEL terminal is left open or as
a synchronization input when the CLKSEL terminal is
grounded. The oscillator output signal is a square wave logic
signal with 50% duty cycle, 180 degrees out-of-phase with
the internal clock signal. This allows opposite phase
synchronization of two 34702 devices.
When the CLKSYN terminal is used as a synchronization
input (CLKSEL terminal grounded), the external resistor R
F
chosen from the chart in
Figure 6
should be used to
synchronize the internal slope compensation ramp to the
external clock. Operation is only recommended between
200 kHz and 400 kHz. The supplied synchronization signal
does not need to be 50% duty cycle. Minimum pulse width is
1.0 μs.
LOW DROPOUT LINEAR REGULATOR (LDO)
The adjustable low dropout linear regulator (LDO) is
capable of supplying a 1.0 A output current. It has a current
limit with retry capability. When the voltage measured across
the current sense resistor reaches the 50 mV threshold, the
control circuit limits the current for 10 ms. If the overcurrent
condition still exists, the linear regulator is turned off and the
retry timer starts to time out. When the timer expires after
100 ms, the LDO tries to power up again for 10 ms,
repeatedly checking for the overcurrent condition. The
current limit of the LDO can be set by using the following
formula:
I
LIM
= 50 mV/RS
Where R
S
is the LDO current sense resistor, connected
between the CS terminal and the LDO terminal output (see
Figure 33
on page
32
), and 50 mV is the typical value of the
LDO current sense comparator threshold voltage.
When no current sense resistor is used, it is still possible
to detect the overcurrent condition by tying the current sense
terminal CS to the VBST voltage. In this case, the overcurrent
condition is sensed by saturation of the linear regulator driver
buffer.
The output voltage of the LDO can be adjusted by means
of an external resistor divider connected to the feedback
control terminal LFB. The linear regulator output voltage can
be adjusted in the range of 0.8 V to V
IN
- LDO dropout
voltage. Power-up, power-down, and fault management are
coordinated with the switching regulator.
POWER SEQUENCING VOLTAGE MARGINING
WATCHDOG TIMER
A watchdog function is available via I
2
C bus
communication. It is possible to select either window
watchdog or time-out watchdog operation, as illustrated in
Figure 16
.
Watchdog time-out starts when the watchdog function is
activated via I
2
C bus sending a Watchdog Programming
command byte, thus determining watchdog operation
(window or time-out) and period duration (refer to
Table 8
,
page
27
). If the watchdog is cleared by receiving a new
Watchdog Programming command through the I
2
C bus, the
watchdog timer is reset and the new time-out period begins.
If the watchdog time expires, the
RST
will become active
(LOW) for a time determined by the RC components of the
RT timer plus 10 ms. After a watchdog time-out, the function
is no longer active.
Figure 16. Watchdog Operation
50% of Watchdog Period
Watchdog Period
Timing Selected via 12C Bus – See Table 4
Watchdog Closed
No Watchdog Clear Allowed
Window Open
for Watchdog Clear
Window Open for Watchdog Clear
Watchdog Period
Timing Selected via I
2
C Bus – See Table 4
Window Watchdog
Time-Out Watchdog
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MC34701EKR2 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 QUICCSUPPLY1 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
MC34702EK 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 QUICCSUPPLY2 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
MC34702EKR2 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 QUICCSUPPLY2 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
MC34703 制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 7WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 7WAY
MC34703PNB 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 QUICC SUPPLY 3 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
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