GTL2002D 查看數據表（PDF） - Philips Electronics

零件编号

产品描述 (功能)

生产厂家

GTL2002D

Bi-directional low voltage translators

Philips Electronics 

OVERVIEW

Description

Within the semiconductor world, there are many I/O standards that have different voltage level requirements for the

input voltage (VIH or VIL) and output voltage (VOH or VOL) typically based on the device operating voltage. These voltage

levels define how the device communicates with other devices and the voltage levels are expressed as a bus standard. A

few of these bus standards include 5 V CMOS, 5 V TTL, 3.3 V LVTTL, 2.5 V AGP graphics port and 1.5 V GTL+ host

bus. Providing a migration path is important in all industry segments because system components used in new designs

must communicate with components using the existing bus infrastructure even if they are operating at higher voltage

levels. Since new devices are designed and produced with advanced sub-micron semiconductor process technologies,

there has to be an easy way to prevent damage to the new device and translate voltage switching levels of the higher

voltage legacy device.

The Philips Semiconductors Gunning Transceiver Logic Translator Voltage Clamp (GTL-TVC) family of bi-directional

low voltage translators is designed in a BiCMOS process for protecting the sensitive I/Os on new advanced sub micron

components. The GTL-TVC devices protect these new devices from the over voltage and ESD conditions applied by the

older, legacy devices and translate the VIH and VOH switching levels. The information presented in this application note

describes the I/O-protection applications and voltage translations of the GTL-TVC family and will enable the design

engineer to successfully interface devices with different I/O voltage levels.

Applications

Voltage Level Shifting

The GTL-TVC devices can be used to interface between devices I/Os operating at different voltage levels. Since the

GTL-TVC device is open drain on both sides, pull up resistors may be needed depending on the I/O interface type (totem

pole or open drain) and the translation direction (High to Low, Low to High, or bi-directional). The GTL-TVC devices

allow translations between any voltages from 1.0 V to 5.0 V as long as the voltage difference between the Gate and

Source voltages is maintained at about 1 V. The recommended circuit in Figure 1 connects the gate (GREF) and

reference drain (DREF) together through a 200 k Ω resistor to a voltage, which should be at least 1.5 V above the

reference Source (SREF) level. This circuit biases the gate to a threshold above the reference source voltage and

compensates for part-to-part threshold variations. Since the gate threshold voltage can vary between 0.6 V and 1 V, if the

GREF to SREF voltage is less than 1 V, the low voltage side high level may be degraded below the SREF voltage

because it can only pull up to a threshold below the GREF voltage.

1.8 V

1.5 V

1.2 V

1.0 V

VCOR

CPU

I/O

200 kΩ

GTL200

GND GREF

SREF DREF

S1 D1

S2 D2

5V

VD

Chipset I/O

Figure 1. Typical Two-bit bi-directional application

1. Bi-directional Translation

For bi-directional translation, the drivers on both sides of the GTL-TVC device must be open drain outputs or at

least they must be controlled in such a way that contention between a High level on an output driver on one side

and a Low level on an output driver on the other side is prevented. The easiest solution is to use open drain

devices (the standard GTL and I2C/SMBus outputs are open drain outputs).

When using open drain devices, it is necessary to use pull up resistors, and they must be sized so as not to

overload the output drivers nor exceed the 15 mA recommended current for use of a GTL-TVC device in a

translation application. If the device is used for I2C bus translation, the resistors must be sized to provide less

than 3 mA of current (I2C devices are specified to drive 3 mA max at 0.4 V).

3

Share Link: