DSP Hotline Techbits : C31 Output Buffer Drive

'C31 Output Buffer Drive Characteristics

The following data is for dynamic loading information only! Driving excessive currents out of the TMS320 drivers will degrade the junctions and eventually cause premature device failure. Safe operating region of these drivers is in the range of 0-10mA constant DC current. Operation outside of this range is not recommended even under low duty cycle conditions, otherwise damage to the output buffer drivers will occur.

This data was collected on PG 5.x 'C31 by driving data pins high against a pull-down resistor and driving data pins low against a pull-up resistor. Voltage across the resistor was measured to determine output high and low currents.

Pull-Up Resistor	V_cc	V_lo	I_ol
10	4.86	2.82	204
20		2.18	134
30.1		1.86	100
49.9		1.52	67.0
60.4		1.42	57.0
82.5		1.30	43.2
100		1.18	36.8
150		1.06	25.3
221		0.90	17.9
301		0.78	13.6
750		0.42	5.92
1K		0.34	4.52

Pull-Up Resistor	V_ss	V_hi	I_oh
10	0.00	1.22	122
20		2.18	109
30.1		2.84	94.4
49.9		3.52	70.5
60.4		3.70	61.3
82.5		3.98	48.2
100		4.10	41.0
150		4.34	28.9
221		4.46	20.2
301		4.58	15.2
750		4.7	6.27
1K		4.76	4.76

Note: short circuit currents for the 'C3x family are approximately:

I_os(H) = 150 mA
I_os(L) = 450 mA

Therefore, the safe operating region of the output buffers lies as shown:

         +--- Iol & Ioh greatly exceed tested limit.
         |    Reliability will be degraded and device damaged.
I(mA)    |
1000|    |        +---- Iol & Ioh exceed tested limits
    |+            |     Vol & Voh will not be guaranteed
 100|    +     |  |   |
    |       +  |      | Safe, Ioh & Iol within tested range
  10|          |      |       Voh & Vol therefore OK
    |  Danger  |  +   |
   1|          |      |+
    |          |      |    +
 0.1|          |      |        +
    |          |      |            +
    ------------------------------------
    0   10   100   1K   10K   100K   1Meg   R(ohm)