- 您现在的位置：买卖IC网 > PDF目录16583 > MAX749CSA-T (Maxim Integrated Products)IC BIAS SUPPLY LCD DIG ADJ 8SOIC PDF资料下载
参数资料
| 型号： | MAX749CSA-T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/12页 |
| 文件大小： | 0K |
| 描述： | IC BIAS SUPPLY LCD DIG ADJ 8SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | LCD 显示器 |
| 电流 - 电源： | 60µA |
| 电源电压： | 2 V ~ 6 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOIC |
| 包装： | 带卷 (TR) |
Digitally Adjustable LCD Bias Supply
Current-Sense Resistor
+4.5V to +6V
INPUT
0.1 μ F
V+
CS
MAX749 DHI
22 μ F
R SENSE
Q1
SMD10P05L
The current-sense resistor limits the peak switch cur-
rent to 140mV/R SENSE , where R SENSE is the value of the
current-sense resistor, and 140mV is the typical cur-
rent-sense comparator threshold (see V+ to CS Voltage
in the Electrical Characteristics).
To maximize efficiency and reduce the size and cost of
the external components, minimize the peak current.
CTRL
DLOW
However, since the output current is a function of the peak
current (Figures 9a-9e), the limit should not be set too low.
ADJ
L1
47 μ H
D1
1N5819
No calculations are required to choose the proper cur-
rent-sense resistor; simply follow this two-step procedure:
1. Determine:
GND
R1
R2
V OUT
(NEGATIVE)
- the minimum input voltage, V IN(MIN),
- the maximum output voltage, V OUT(MAX) , and
- the maximum output current, I OUT(MAX) .
22 μ F
For example, assume that the output voltage must be
V OUT(MIN) = -R1(13.33 μ A)
V OUT(MAX) = -(R1+R2)(13.33 μ A)
C COMP
30V
adjustable to -24V (V OUT(MAX) = -24V) at up to 30mA
(I OUT(MAX) = 30mA). The supply voltage ranges from
4.75V to 6V (V IN(MIN) = 4.75V).
Figure 8. Using a Potentiometer to Adjust the Output Voltage
counter rolls over and sets the DAC to -V OUT(MIN) ,
where -V OUT(MIN) = R FB x 6.66μA. In other words, a sin-
gle rising edge of ADJ increments the DAC output by
one, and 63 rising edges of ADJ decrement the DAC
output by one.
Potentiometer Adjustment
It is also possible to adjust the output voltage using a
potentiometer instead of the internal DAC (Figure 8). On
power-up (V+ applied), the internal current source is set
to mid-scale, or 13.33μA. Choose R1 and R2 with the fol-
lowing equations:
R1 = -V OUT(MIN) /13.33μA
R2 = -V OUT(MAX) /13.33μA - R1.
Where the potentiometer can be varied from 0 (producing
V OUT(MIN) ) to R2 ? (producing V OUT(MAX) ). Notice that ADJ
is connected to ground, allowing the device to be shut
down.
PWM Adjustment
A positive pulse-width modulated (PWM) logic signal
(e.g., from a microcontroller) can control the MAX749’s
output voltage. Use the PWM signal to pull up the FB
pin through a suitable resistor. An RC network on the
PWM output would also be required. In this configura-
tion, the longer the PWM signal remains high, the more
negative the MAX749’s output will be driven.
2. In Figures 9a-9e, locate the graph drawn for the
appropriate output voltage (which is either the
desired output voltage or, if that is not shown, the
graph for the nearest voltage more negative than the
desired output). On this graph find the curve for the
highest R SENSE (the lowest current limit) with an out-
put current that is adequate at the lowest input
voltage.
In this example, select the -24V output graph, Figure 9d.
We then want a curve where I OUT is ≥ 30mA with a 4.75V
input. The 0.3 ? R SENSE graph shows 25mA of output cur-
rent with a 4.75V input, so we look next at the 0.25 ?
R SENSE graph. It shows I OUT = 30mA for V IN = 4.75V and
V OUT = -24V. Therefore select R SENSE = 0.25 ? . This pro-
vides a current limit in the range 440mA to 720mA.
Alternatively, a 0.2 ? sense resistor can be used. This
gives a current limit in the range 550mA to 900mA, but
enables over 40mA to be generated at -24V with input
voltages down to 4.5V. A 0.2 ? resistor may be easier to
obtain than an 0.25 ? resistor.
The theoretical design curves shown in Figures 9a-9e
assume the minimum (worst-case) value for the current-
limit comparator threshold. Having selected the cur-
rent-sense resistor, the maximum current limit is given
by 180mV/R SENSE . Use the maximum current-limit fig-
ure when choosing the transistor, coil, and diode.
IRC (see Table 2) makes surface-mount resistors with pre-
ferred values including: 0.1 ? , 0.2 ? , 0.3 ? , 0.5 ? , and 1.0 ? .
8
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| M1WXK-1436J | IDC CABLE - MPL14K/MC14G/X |
| GMM10DRKI-S13 | CONN EDGECARD 20POS .156 EXTEND |
| 1-846291-1 | LGH-4 LEAD DBL MLD ENDS |
| SRP7030-R68FM | INDUCTOR POWER 0.68UH SHIELD SMD |
| GCM18DRKI-S13 | CONN EDGECARD 36POS .156 EXTEND |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX749EPA | 功能描述:显示驱动器和控制器 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX749EPA+ | 功能描述:其他电源管理 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX749ESA | 功能描述:显示驱动器和控制器 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX749ESA+ | 功能描述:其他电源管理 Digitally Adjustable LCD Bias Supply RoHS:否 制造商:Texas Instruments 输出电压范围: 输出电流:4 mA 输入电压范围:3 V to 3.6 V 输入电流: 功率耗散: 工作温度范围:- 40 C to + 110 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-48 封装:Reel |
| MAX749ESA+ | 制造商:Maxim Integrated Products 功能描述:IC LCD BIAS SUPPLY 8-SOIC 制造商:Maxim Integrated Products 功能描述:IC, LCD BIAS SUPPLY, 8-SOIC |
发布紧急采购，3分钟左右您将得到回复。