84515IBZ View Datasheet(PDF) - Renesas Electronics

Part Name

Description

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84515IBZ

Low-Voltage, Single Supply, SPST, Analog Switches

Renesas Electronics 

ISL84514, ISL84515

Test Circuits and Waveforms (Continued)

IMPEDANCE

ANALYZER

V+

C

NO OR NC

IN 0V OR V+

COM

GND

FIGURE 5. CAPACITANCE TEST CIRCUIT

Detailed Description

The ISL84514 and ISL84515 analog switches offer precise

switching capability from a single 2.4V to 12V supply with

low ON-resistance, and high-speed operation. The devices

are especially well suited to portable battery powered

equipment thanks to the low operating supply voltage (2.4V),

low power consumption (5µW), low leakage currents (2nA

max), and the tiny SOT-23 packaging. High frequency

applications also benefit from the wide bandwidth, and the

very high off-isolation.

Supply Sequencing and Overvoltage Protection

With any CMOS device, proper power supply sequencing is

required to protect the device from excessive input currents,

which might permanently damage the IC. All I/O pins contain

ESD protection diodes from the pin to V+ and to GND (see

Figure 6). To prevent forward biasing these diodes, V+ must

be applied before any input signals, and input signal

voltages must remain between V+ and GND. If these

conditions cannot be guaranteed, then one of the following

two protection methods should be employed.

Logic inputs can easily be protected by adding a 1k

resistor in series with the input (see Figure 6). The resistor

limits the input current below the threshold that produces

permanent damage, and the sub-microamp input current

produces an insignificant voltage drop during normal

operation.

Adding a series resistor to the switch input defeats the

purpose of using a low rON switch, so two small signal

diodes can be added in series with the supply pins to provide

overvoltage protection for all pins (see Figure 6). These

additional diodes limit the analog signal from 1V below V+ to

1V above GND. The low leakage current performance is

unaffected by this approach, but the switch resistance may

increase, especially at low supply voltages

OPTIONAL

PROTECTION

RESISTOR

IN

VNO OR NC

OPTIONAL PROTECTION

DIODE

V+

VCOM

GND

OPTIONAL PROTECTION

DIODE

FIGURE 6. OVERVOLTAGE PROTECTION

Power-Supply Considerations

The ISL8451x construction is typical of most CMOS analog

switches, except that there are only two supply pins: V+ and

GND. Unlike switches with a 13V maximum supply voltage,

the ISL8451x 15V maximum supply voltage provides plenty

of room for the 10% tolerance of 12V supplies, as well as

margin for overshoot and noise spikes.

The minimum recommended supply voltage is 2.4V. 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” tables beginning on page 3

and “Typical Performance Curves” beginning on page 9 for

details.

V+ and GND power the internal CMOS switches and set

their analog voltage limits. These supplies also power the

internal logic and level shifters. The level shifters convert the

input logic levels to switched V+ and GND signals to drive

the analog switch gate terminals.

FN6025 Rev 5.00

June 9, 2014

Page 7 of 12

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