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參數(shù)資料
| 型號(hào)： | MAX749CPA |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Digitally Adjustable LCD Bias Supply |
| 中文描述： | SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | 0.300 INCH, PLASTIC, DIP-8 |
| 文件頁(yè)數(shù)： | 6/12頁(yè) |
| 文件大?。?/td> | 105K |
| 代理商： | MAX749CPA |
M
Once turned off, a one-shot holds the switch off for a
minimum of 1μs, and the switch either stays off (if the
output is in regulation), or turns on again (if the output
is out of regulation).
With light loads, the transistor switches for one or more
cycles and then turns off, much like a traditional PFM
converter. With heavy loads, the transistor stays on until
the switch current reaches the current limit; it then
shuts off for 1μs, and immediately turns on again until
the next time the switch current reaches its limit. This
cycle repeats until the output is in regulation.
Output V oltage Control
The output voltage is set using a single external resistor
and the internal current-output DAC (Figure 1). The full-
scale output voltage is set by selecting the feedback
resistor, R
FB
. The output voltage is controlled from 33%
to 100% of the full-scale output by an internal 64-step
DAC/counter.
On power-up or after a reset, the counter sets the DAC
output to mid-range. Each rising edge of ADJ incre-
ments the DAC output. When incremented beyond full
scale, the counter rolls over and sets the DAC to the
minimum value. In this way, a single pulse applied to
ADJ increases the DAC set point by one step, and 63
pulses decrease the set point by one step.
Table 1 is the logic table for the CTRL and ADJ inputs,
which control the internal DAC and counter. Figures 3-7
show various timing specifications and different ways of
incrementing and resetting the DAC, and of placing it in
the low-power standby mode. As long as the timing
specifications for ADJ and CTRL are observed, any
sequence of operations can be implemented.
Table 1. Input Truth Table
Digitally Adjustable LCD Bias S upply
6
______________________________________________________________________________________
L1
47
μ
H
DLOW
6-BIT
CURRENT-OUTPUT
DAC
REF
MAXIMUM
ON-TIME
ONE-SHOT
MAX749
V
(NEGATIVE)
22
μ
F
0.1
μ
F
V+
DHI
FB
GND
R
SENSE
Q1
ZTX750
D1
1N5819
R
BASE
470
22
μ
F
30V
C
COMP
R
FB
TRIG
MINIMUM
OFF-TIME
ONE-SHOT
TRIG
Q
Q
Q
S
R
FLIP-FLOP
VOLTAGE
COMPARATOR
140mV
+2V TO +6V
INPUT
CURRENT
COMPARATOR
Figure 2. Switch-Mode Power-Supply Section Block Diagram
ADJ
Low
CTRL
Low
RESULT
Shut down
High
Low
Reset counter to mid-range. The
device is not shut down.
X
High
High
On
Increment the counter
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX749CPA+ | 功能描述:顯示驅(qū)動(dòng)器和控制器 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX749CPA+T | 制造商:Maxim Integrated Products 功能描述: |
| MAX749CSA | 功能描述:顯示驅(qū)動(dòng)器和控制器 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX749CSA+ | 功能描述:其他電源管理 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
| MAX749CSA+T | 功能描述:顯示驅(qū)動(dòng)器和控制器 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
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