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PDF AN10145 Data sheet ( Hoja de datos )
| Número de pieza | AN10145 | |
| Descripción | Bi-directional low voltage translators | |
| Fabricantes | NXP Semiconductors | |
| Logotipo |  |
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INTEGRATED CIRCUITS
DREF
GREF
D1
D22
SREF
S1
S22
ABSTRACT
Philips Semiconductors Gunning Transceiver Logic Translator Voltage Clamp (GTL-TVC)
bi-directional low voltage translators are used in bi-directional signaling voltage level translation
applications. Voltage translation can be from any voltage between 1.0 V to 5.0 V to any voltage
between 1.0 V to 5.0 V without need for directional control. Device operation, resistor sizing and
typical applications are discussed in this application note.
AN10145
Bi-directional low voltage translators
GTL2000, GTL2002, GTL2010
Supersedes data of 2002 Dec 16
Alma Anderson – Senior Design Engineer
Jean-Marc Irazabal – Technical Marketing Manager
Steve Blozis – International Product Manager
Specialty Logic Product Line
Interface Products Business Line
2004 Aug 11
Philips
Semiconductors
Free Datasheet http://www.datasheet4u.com/
1 page  
Cross-Bar Technology (CBT) Like Behavior
The large NMOS pass transistors used in the GTL-TVC devices are very similar to the large NMOS pass transistors used
in CBT devices. However unlike the CBT devices that use internal drivers to control the gate of the NMOS pass
transistor, the gate pin of the GTL-TVC devices is directly connected to the gate of each transistor. In principle the
GTL-TVC devices can be used like CBT devices except that the gate input capacitance is much larger than a normal
CBT device. When using the GTL-TVC devices as CBT devices, the gate pin (GREF) is driven by external logic to the
power supply, to enable it, or to ground to disable it, and the SREF and DREF pins can be used as an additional channel
as shown in Figure 3.
VDD
Chip set
GTL2002
GND GREF
SREF DREF
S1 D1
S2 D2
Control
5V
VDD
Chipset I/O
Figure 3. Cross Bar Technology like Application
Note: If a 5 V to 3.3 V translation is wanted, best results are achieved using the bias circuit of the GTL-TVC with the
SREF at 3.3 V. Additionally, when used as a CBT function with the gate at VDD and the input at VDD, the maximum pass
voltage will be ~ VDD – 1 V because the output is shifted down by a threshold compared to the gate voltage.
Features
The GTL-TVC family has several features that benefit a system designer when designing an interface between devices
with different I/O voltage levels.
Device Construction – The GTL-TVC devices are of a very simple design. The only required connections are GND,
gate of the reference transistor (GREF), drain of the reference transistor (DREF) and source of the reference transistor
(SREF) and then any of the Dn/Sn I/O pairs needed for voltage level translations.
• Any transistor Dn or Sn I/O pair can be used as the source or drain of the reference transistor (SREF or DREF). This
makes it easier to route signals to and from the device.
• All the transistors are on one die, which is manufactured with very tight process control. This provides a very low
spread of VO relative to SREF or DREF.
• It is easy to change the SREF voltage allowing the system designer an easy migration path to even lower voltages
(e.g. 1.5 V or 1.2 V).
• Dn /Sn I/O pairs are matched on either side of the devices (e.g., flow through pinout) which offers easy trace
routing.
No Active Control Logic – As shown in Figure 4, the GTL-TVC is a passive device and there is no active control logic.
This means there is no supply power (VDD) required for device operation.
Figure 4. GTL20XX Logic Diagram
5
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0 0.25 0.5 0.75
0.0E+00
-2.0E-03
-4.0E-03
-6.0E-03
-8.0E-03
VDDref = 5.0v
VDDpass = 3.3v
RDn = 150 ohms
RDref = 200k
-1.0E-02
-1.2E-02
-1.4E-02
-1.6E-02
-1.8E-02
-2.0E-02
-2.2E-02
1 1.25 1.5 1.75
VSn (V)
VSref = 2.5v
2 2.25 2.5
25 deg C
85 deg C
-40 deg C
Figure 13. V-I Electrical Characteristics at VSREF = 2.5 Volt and VDDREF = 5.0 Volt
Figures 11, 12 and 13 show the SREF at 2.5 V with VDDREF voltages of 3.3 V, 4.0 V, and 5.0 V respectively. Note that
when VDDREF is 3.3 V, with only 0.8 V between VDDREF and the SREF voltage, the cold temperature curve turns off
before the source voltage reaches the SREF voltage. With VDDREF voltages of 4.0 V and 5.0 V, the behavior returns to
normal where the turn off point is the SREF voltage, independent of temperature. The same pass transistor at hot
temperatures has a higher on resistance so it starts to shut off sooner as the source voltage approaches the SREF voltage.
CBT Like Electrical characteristics
CBT like characteristics are tested using a setup as shown in Figure 14.
m
Figure 14 – CBT like Test Set Up
Figure 15 shows typical pass transistor on resistance (RON) as a function of source voltage with the gate at 5 V and
Isource = 64 mA, Figure 16 shows RON with Isource = 15 mA. As can be clearly seen in these figures, the RON changes only
slightly as long as the source voltage is less than the gate to source voltage necessary to conduct an Idsat equal to the
current source current (64 mA for Figure 15 and 15 mA for Figure 16). The RON increases rapidly as the transistor is
unable to conduct the high current. CBT functions are generally used with dynamic currents rather than static currents.
11
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| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet AN10145.PDF ] | |
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