LT1016IS8 datasheet(15/20 Pages) LINER

15 / 20 page

LT1016

APPE DIX A

About Level Shifts

The TTL output of the LT1016 will interface with many

circuits directly. Many applications, however, require some

form of level shifting of the output swing. With LT1016

based circuits this is not trivial because it is desirable to

maintain very low delay in the level shifting stage. When

designing level shifters, keep in mind that the TTL output

of the LT1016 is a sink-source pair (Figure A1) with good

ability to drive capacitance (such as feedforward capaci-

tors).

Figure A2 shows a noninverting voltage gain stage with a

15V output. When the LT1016 switches, the base-emitter

voltages at the 2N2369 reverse, causing it to switch very

quickly. The 2N3866 emitter-follower gives a low imped-

ance output and the Schottky diode aids current sink

capability.

Figure A3 is a very versatile stage. It features a bipolar

swing that may be programmed by varying the output

transistor’s supplies. This 3ns delay stage is ideal for

driving FET switch gates. Q1, a gated current source,

switches the Baker-clamped output transistor, Q2. The

heavy feedforward capacitor from the LT1016 is the key to

low delay, providing Q2’s base with nearly ideal drive. This

capacitor loads the LT1016’s output transition (Trace A,

Figure A4), but Q2’s switching is clean (Trace B, Figure A4)

with 3ns delay on the rise and fall of the pulse.

Figure A5 is similar to Figure A2 except that a sink

transistor has replaced the Schottky diode. The two emit-

ter-followers drive a power MOSFET which switches 1A at

15V. Most of the 7ns to 9ns delay in this stage occurs in

the MOSFET and the 2N2369.

When designing level shifters, remember to use transis-

tors with fast switching times and high fTs. To get the kind

of results shown, switching times in the ns range and fTs

approaching 1GHz are required.

–

LT1016

0.068

µF

GND

LATCH

V –

1MHz TO 10MHz

CRYSTAL

V +

1016 AI04

OUTPUT

–

LT1016

–

LT1193

RESET (NORMALLY OPEN)

900

Ω

200

Ω

CALIBRATE

1k*

9k*

LOAD

Ω

CARBON

TRIP SET

0mA TO 250mA = 0V TO 2.5V

28V

2N3866

2N2369

330

Ω

2.4k

–5V

33pF

300

Ω

* = 1% FILM RESISTOR

A1 AND A2 USE

±5V SUPPLIES

1016 AI05

1MHz to 10MHz Crystal

Oscillator

18ns Fuse with Voltage Programmable Trip Point

TYPICAL APPLICATIO S

LT1016IS8 Datasheet(PDF) 15 Page - Linear Technology

LT1016IS8 Datasheet(HTML) 15 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL