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参数资料
| 型号： | PS323ESAX |
| 厂商： | PERICOM SEMICONDUCTOR CORP |
| 元件分类： | 多路复用及模拟开关 |
| 英文描述： | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
| 封装： | SO-8 |
| 文件页数： | 8/12页 |
| 文件大小： | 259K |
| 代理商： | PS323ESAX |
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5
PS8188F
03/10/05
PS323
Precision, Single Supply SPST Analog Switch
Application Information
The PS323 dual analog switch precisely switches inputs with a
single 2.7V to 12V supply, low On-Resistance (30-ohm) and high
speed operation (tON = 85ns, tOFF = 25ns). The devices are suited
to portable battery powered equipment due to a low supply voltage
(2.7V), low power consumption (5mW), and low leakage currents
(0.1nA). High frequency applications benefit from the high
bandwidth, high off isolation, and low crosstalk.
Proper Power Supply Sequencing & Over-voltage
Protection
With any CMOS device, proper power supply sequencing is needed
to protect the device from excessive input currents, which may
permanently damage the IC. All I/O pins contain ESD protection
diodes from the pin to V+ and to GND (see Figure 9 below).
To prevent forward biasing of these diodes, V+ must be applied
before any input signals, and input signals must swing between
V+ and GND. If these conditions cannot be guaranteed, then one
of two suggested protection methods must be employed. Protect
the logic inputs by adding a 1k-ohm resistor in series with the
input (see Figure 9). The resistor limits the currents below the
threshold that can cause permanent damage to sub-micro Amp
levels. This reduced input current produces an insignificant voltage
drop during normal operation. A series resistor is not desirable, but
small-signal diodes can be added in series with the supply pins to
provide over-voltage protection for the IC. The diodes limit the
analog signal from 1V below V+ to 1V above GND. The leakage
current will remain low, but the switch resistance may increase at low
supply voltages.
V+
Positive Supply
COM
NO
Vg
V-
Figure 1. Overvoltage Protection
Power-Supply Considerations
The PS323 construction is typical of most CMOS analog switches,
except that they have voltage supply pins: V+ and GND. These
pins power the internal CMOS switches and set the analog voltage
limits. Unlike switches with a 12V maximum supply voltage, the
PS323 is made from a 17V-supply voltage technology that provides
room for 10-20% tolerance on 12V supplies. This technology gives
room for overshoot and noise spikes. While the minimum
recommended supply voltage is 2.7V, it is important to note that
the input signal-range, switching times, and on-resistance degrade
at lower supply voltages. Refer to the electrical specifications for
details. V+ and GND also power the internal logic drivers (turn the
switch on & off). These switches can be operated with bipolar
supplies if the voltage range from V- (at the GND pin) to V+ does
not exceed a total of 12V.
Logic-Level Thresholds
The switch logic is TTL compatible (0.8V & 2.4V) over a supply
range of 3V to 11V. At 12V the VIH level is about 2.5V. This is below
the TTL guaranteed high output minimum level of 2.8V, but noise
margin is reduced. For best results with a 12V supply, use logic
drive that provides a VOH greater than 3V. The digital input stages
draw supply current whenever the digital input voltage is not at
one of the supply rails. Driving the digital input signals from GND
to V+ with a fast transition time minimizes power dissipation.
High-Frequency Signal Passing/Isolation
In 50-ohm systems, signal response is flat even past 300MHz.
An OFF switch is like a capacitor and passes high frequencies
with low attenuation, resulting in signal passing from the switch
input to output. OFF Isolation is the resistance to passing signals
while the switch is OFF, while Crosstalk indicates the amount of
signal noise that crosses over from one switch to another. The
OFF Isolation is about 50dB in 50-ohm systems. Larger load
impedances reduce Off Isolation and Crosstalk due to the voltage
divider action of the switch OFF impedance and the load.
Leakage Current
Reverse ESD protection diodes are internally connected between
each analog-signal pin and both V+ and GND. One of these diodes
conducts if any analog signal exceeds V+ or GND.
Most of the analog leakage current comes from the ESD diodes to
V+ or GND. Although the ESD diodes on a given signal pin are
identical and therefore fairly well balanced, they are reverse biased
differently. Either V+ or GND and the analog signal bias each
diode. Hence, leakage currents will vary as the signal varies. The
difference in the diode leakage currents to the V+ and GND pins
creates the analog signal-path leakage current. Also, analog leakage
currents flow between each pin and one of the supply terminals,
not to the other switch terminal. This is why both sides of a given
switch can show leakage currents of the same or opposite polarity. There
is no connection between the analog-signal paths and V+ or GND.
相关PDF资料 |
PDF描述 |
|---|---|
| PS323CUAE | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
| PS323EUAE | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
| PS323EUAX | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
| PS323CSAX | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
| PS323CUA | DUAL 1-CHANNEL, SGL POLE SGL THROW SWITCH, PDSO8 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| PS323EUAX | 制造商:PERICOM 制造商全称:Pericom Semiconductor Corporation 功能描述:Precision, Single-Supply SPST Analog Switches |
| PS324 | 制造商:PERICOM 制造商全称:Pericom Semiconductor Corporation 功能描述:Precision, Single-Supply SPST Analog Switches |
| PS32-40-4MNS-A-SP | 制造商:DANAHER - INDUSTRIAL/SPECIALTY 功能描述:50-150PSI (3.4-10.3BAR) 1/4NPTM 316SS, SPST/NO, SPADE TERMINAL |
| PS324CPA | 制造商:PERICOM 制造商全称:Pericom Semiconductor Corporation 功能描述:Precision, Single-Supply SPST Analog Switches |
| PS324CSA | 制造商:PERICOM 制造商全称:Pericom Semiconductor Corporation 功能描述:Precision, Single-Supply SPST Analog Switches |
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