GTL2010 Datasheet, PDF (12/15 Pages) NXP Semiconductors – 10-bit GTL Processor Voltage Clamp

GTL2010
10-BIT BIDIRECTIONAL LOW-VOLTAGE TRANSLATOR
SCDS221 – SEPTEMBER 2006
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APPLICATION INFORMATION (continued)
Sizing Pullup Resistor
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:
Resistor
value
(W)
+
Pullup
voltage (V)
0.015 A
*
0.35
V
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)
VOLTAGE
5.0 V
3.3 V
2.5 V
1.8 V
1.5 V
1.2 V
15 mA
NOMINAL
310
197
143
97
77
57
+10%
341
217
158
106
85
63
PULLUP RESISTOR VALUE (Ω)
10 mA
NOMINAL
+10%
465
512
295
325
215
237
145
160
115
127
85
94
(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
3 mA
NOMINAL
1550
983
717
483
383
283
+10%
1705
1082
788
532
422
312
12
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