Datasheet

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Sizing Pullup Resistor
Resistor value
(
W
)
+
Pullup voltage (V) * 0.35 V
0.015 A
GTL2010
10-BIT BIDIRECTIONAL LOW-VOLTAGE TRANSLATOR
SCDS221 – SEPTEMBER 2006
APPLICATION INFORMATION (continued)
The pullup resistor value should limit the current through the pass transistor when it is in the on state to about
15 mA. This ensures a pass voltage of 260 mV to 350 mV. If the current through the pass transistor is higher
than 15 mA, the pass voltage also is higher in the on state. To set the current through each pass transistor at
15 mA, the pullup resistor value is calculated as:
Table 1 shows resistor values for various reference voltages and currents at 15 mA, 10 mA, and 3 mA. The
resistor value shown in the +10% column, or a larger value, should be used to ensure that the pass voltage of
the transistor would be 350 mV or less. The external driver must be able to sink the total current from the
resistors on both sides of the GTL device at 0.175 V, although the 15 mA only applies to current flowing through
the GTL2010.
Table 1. Pullup Resistor Values
(1) (2) (3)
PULLUP RESISTOR VALUE ( Ω )
15 mA 10 mA 3 mA
VOLTAGE
NOMINAL +10% NOMINAL +10% NOMINAL +10%
5.0 V 310 341 465 512 1550 1705
3.3 V 197 217 295 325 983 1082
2.5 V 143 158 215 237 717 788
1.8 V 97 106 145 160 483 532
1.5 V 77 85 115 127 383 422
1.2 V 57 63 85 94 283 312
(1) Calculated for V
OL
= 0.35 V
(2) Assumes output driver V
OL
= 0.175 V at stated current
(3) +10% to compensate for V
DD
range and resistor tolerance
12
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