BUF602IDBVT datasheet(16/22 Pages) TI

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DESIGN-IN TOOLS

DEMONSTRATION BOARDS

MACROMODELS AND APPLICATIONS

√4kTR

OUTPUT CURRENT AND VOLTAGE

e2n ) inRS

) 4kTRS

(6)

THERMAL ANALYSIS

BUF602

SBOS339 – OCTOBER 2005

graph is bounded by a Safe Operating Area of 1W

maximum internal power dissipation. Superimposing

resistor load lines onto the plot shows that the

BUF602 can drive

±3V into 25Ω or ±3.5V into 50Ω

without exceeding the output capabilities or the 1W

Two PC boards are available to assist in the initial

dissipation limit.

evaluation of circuit performance using the BUF602 in

its two package styles. Both are available free, as

The minimum specified output voltage and current

unpopulated PC boards delivered with descriptive

over-temperature are set by worst-case simulations at

documentation. The summary information for these

the cold temperature extreme. Only at cold startup

boards is shown in Table 1.

will the output current and voltage decrease to the

numbers shown in the Electrical Characteristic tables.

Table 1. Demo Board Listing

As the output transistors deliver power, the junction

LITERATURE

temperatures will increase, decreasing both VBE

PACKA

BOARD PART

REQUEST

(increasing the available output voltage swing) and

PRODUCT

NUMBER

increasing the current gains (increasing the available

BUF602ID

SO-8

DEM-BUF-SO-1A

SBAU118

output

current).

steady-state

operation,

the

BUF602IDBV

SOT23-5

DEM-BUF-SOT-1A

SBAU117

available output voltage and current will always be

greater than that shown in the over-temperature

To request either of these boards, use the Texas

specifications,

since

the

output

stage

junction

Instruments web site (www.ti.com).

temperatures will be higher than the minimum

specified operating ambient.

For a buffer, the noise model is shown in Figure 33.

SUPPORT

Equation 6 shows the general form for the output

Computer simulation of circuit performance using

noise voltage using the terms shown in Figure 33.

SPICE

often

useful

when

analyzing

the

performance of analog circuits and systems. This is

particularly true for video and RF amplifier circuits

where parasitic capacitance and inductance can have

a major effect on circuit performance. A SPICE model

for the BUF602 is available through the TI web site

(www.ti.com). These models do a good job of

predicting small-signal AC and transient performance

under a wide variety of operating conditions. They do

not do as well in predicting the harmonic distortion or

dG/dP characteristics. These models do not attempt

distinguish

between

package

types

their

small-signal AC performance.

Figure 33. Buffer Noise Analysis Model

The BUF602 provides output voltage and current

capabilities that are not usually found in wideband

buffers. Under no-load conditions at 25

°C, the output

voltage typically swings closer than 1.2V to either

supply rail; the +25

°C swing limit is within 1.2V of

Due to the high output power capability of the

either rail. Into a 15

Ω load (the minimum tested load),

BUF602, heatsinking or forced airflow may be

it is tested to deliver more than

±60mA.

required

under

extreme

operating

conditions.

Maximum desired junction temperature will set the

The specifications described above, though familiar in

maximum allowed internal power dissipation as

the industry, consider voltage and current limits

described below. In no case should the maximum

separately. In many applications, it is the voltage

junction temperature be allowed to exceed 150

°C.

current, or V-I product, which is more relevant to

circuit operation. Refer to the Buffer Output Voltage

Operating junction temperature (TJ) is given by TA +

and Current Limitations plot (Figure 16) in the Typical

PD × θJA. The total internal power dissipation (PD) is

Characteristics. The X and Y axes of this graph show

the sum of quiescent power (PDQ) and additional

the

zero-voltage

output

current

limit

and

the

power dissipated in the output stage (PDL) to deliver

zero-current output voltage limit, respectively. The

load power. Quiescent power is simply the specified

four quadrants give a more detailed view of the

no-load supply current times the total supply voltage

BUF602 output drive capabilities, noting that the

across the part. PDL will depend on the required

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