TMC2084-HT SMSC, TMC2084-HT Datasheet - Page 72

• Manufacturer Part Number: TMC2084-HT
• Description: IC CTRLR CIRCLINK TM 48-TQFP
• Manufacturer: SMSC
• Series: CircLink™r

Specifications of TMC2084-HT

• Controller Type: I/O Controller
• Interface: Transceiver
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP, 48-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Other names: 638-1025

4.2
Revision 0.2 (10-23-08)
Output Current from Shared Pins
The output current from the PD7/nRCNERR pin is specified as I
drain no current when it is used as the OUTPUT PORT pin (PD7) (PGS2 = Low). Otherwise, configuration
by the shared pin can not be performed correctly.
In the following example, the low level on PD7 pin turns on the LED; R1 limits LED current; and the pull-
down resister R2 is used for configuration (PGS2 = Low) using the shared pin during reset. The voltage
level on PD7 pin during the reset (PD7 is in high-impedance state) will be as follows:
Assuming Vdd = 3.3 V, Vf = 2 V, R1 = 330 Ω and R2 = 10 kΩ, the current (I
Vdd is:
Thus, the voltage level of PD7 pin during reset is I
maximum low level input voltage 0.8V. This makes the configuration PGS2 = Low impossible.
The pull-up resister R2 in the figure below allows the configuration PGS2 = High correctly because no
current flows through R2 during high-impedance state in reset phase. This enables LED to monitor the
nRCNERR signal.
The same considerations are needed for other shared pins (PD6 - 0 and TXD). In the high-impedance
state during reset, careful attention should be paid for the current and voltage caused by the pull-up and
pull-down resisters.
I
R2
nRCNERR
PD7
= (Vdd - Vf) ÷(R1 + R2)
= (3.3 V - 2 V) ÷ (330 Ω + 10000 Ω)
(PD7)
Hi-Z state
DATASHEET
I
OL
R2
<
R2
4 mA
I
R2
Page 72
Vdd=3.3V
LED
Vf=2V
R1
R2
.
. =
LED
× R2 = 126μA × 10 kΩ
126 μA.
OL
= 4 mA (Max). However, this pin should
Standalone Mode CircLink
.
. =
R2
1.3V and this exceeds the
) flows in R1 and R2 from
SMSC TMC2084
TM
Datasheet
Controller