LT6201CS8 datasheet(21/26 Pages) LINER

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62001fd

LT6200/LT6200-5

LT6200-10/LT6201

Figure 2 shows the input and output waveforms of the

LT6200 driven into clipping while connected in a gain of

AV = 1. In this photo, the input signal generator is clipping

at ±35mA, and the output transistors supply this generator

current through the protection diodes.

APPLICATIONS INFORMATION

VCC

2.5V

VEE

–2.5V

6200 F02

Figure 2. VS = ±2.5V, AV = 1 with Large Overdrive

ESD

The LT6200 has reverse-biased ESD protection diodes on

all inputs and outputs, as shown in Figure 1. If these pins

are forced beyond either supply, unlimited current will ﬂow

through these diodes. If the current is transient and limited

to 30mA or less, no damage to the device will occur.

Noise

The noise voltage of the LT6200 is equivalent to that of

a 56Ω resistor—and for the lowest possible noise, it is

desirable to keep the source and feedback resistance

at or below this value (i.e., RS + RG//RFB ≤ 56Ω). With

RS + RG//RFB = 56Ω the total noise of the ampliﬁer is:

en = √(0.95nV)2 + (0.95nV)2 = 1.35nV. Below this resis-

tance value the ampliﬁer dominates the noise, but in the

resistance region between 56Ω and approximately 6kΩ,

the noise is dominated by the resistor thermal noise. As

the total resistance is further increased, beyond 6k, the

noise current multiplied by the total resistance eventually

dominates the noise.

For a complete discussion of ampliﬁer noise, see the

LT1028 data sheet.

Power Dissipation

The LT6200 combines high speed with large output cur-

rent in a small package, so there is a need to ensure that

the die’s junction temperature does not exceed 150°C.

The LT6200 is housed in a 6-lead TSOT-23 package. The

package has the V – supply pin fused to the lead frame to

enhance the thermal conductance when connecting to a

ground plane or a large metal trace. Metal trace and plated

through-holes can be used to spread the heat generated by

the device to the backside of the PC board. For example,

on a 3/32" FR-4 board with 2oz copper, a total of 270mm2

connects to Pin 2 of the LT6200 (in a TSOT-23 package)

bringing the thermal resistance, θJA, to about 135°C/W.

Without an extra metal trace beside the power line con-

necting to the V– pin to provide a heat sink, the thermal

resistance will be around 200°C/W. More information on

thermal resistance with various metal areas connecting

to the V – pin is provided in Table 1.

Table 1. LT6200 6-Lead TSOT-23 Package

COPPER AREA

TOPSIDE (mm2)

BOARD AREA

(mm2)

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

270

2500

135ºC/W

100

2500

145ºC/W

2500

160ºC/W

2500

200ºC/W

Device is mounted on topside.

Junction temperature TJ is calculated from the ambient

temperature TA and power dissipation PD as follows:

TJ = TA + (PD • θJA)

The power dissipation in the IC is the function of the supply

voltage, output voltage and the load resistance. For a given

supply voltage, the worst-case power dissipation PD(MAX)

occurs at the maximum quiescent supply current and at

the output voltage which is half of either supply voltage

(or the maximum swing if it is less than half the supply

voltage). PD(MAX) is given by:

PD(MAX) = (VS • IS(MAX)) + (VS/2)2/RL

Example: An LT6200 in TSOT-23 mounted on a 2500mm2

area of PC board without any extra heat spreading plane

connected to its V– pin has a thermal resistance of

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