TISPPBL2SD
PROGRAMMABLE OVERVOLTAGE PROTECTORS
FOR ERICSSON COMPONENTS PBL 3xxx SLICS
AUGUST 1999
PBL 3762A SLIC RING AND TIP VOLTAGE WITHSTAND
vs
TIME
15
10
5
0.25 µs
1 µs
10 ms
0
Time
VBAT
-50
-60
-70
VBAT - 20 V
10 ms
1 µs
-80
-90
D.C. and 10 ms pulse rating increased
to -70 V (independent of VBAT value)
VBAT - 40 V
-100
-110
by use of series battery feed diode
0.25 µs
AI6XBC
VBAT - 70 V
-120
Figure 15. TRANSIENT LIMITS FOR PBL 3762A WITHSTAND VOLTAGE
In the negative polarity, the PBL 3762A RING or TIP voltage must not exceed VBAT - 70. Continuously the
PBL 3762A can withstand a VBAT of -70 V and this implies a maximum peak voltage of -140 V. Figure 15 is
drawn for a VBAT of -50 V and so that the peak voltage becomes -120 V.
For 250 ns, the PBL 3762A will be able to withstand a voltage between VBAT -40V and VBAT -70 V or -90 V
and -120 V in this case. For 1 µs, the PBL 3796 will be able to withstand a voltage between VBAT -20V and
VBAT -40 V or -70 V and -90 V in this case. For 10 ms, the PBL 3796 will be able to withstand a voltage
between VBAT and VBAT -20 V or -50 V and -70 V in this case. By adding a series feed diode in the battery
feed the d.c. and 10 ms voltage withstands increase to -70 V, independent of the actual VBAT value.To protect
against negative overvoltage, the TISPPBL2S negative limiting voltage must be equal to or less than these
voltage values during the specified time periods.
The following table lists the protection requirements of three selections from different SLIC families. Two, the
PBL 3796 and the PBL 3762A, specify voltage withstand. The PBL 3796 specifies the negative voltages in
absolute terms and the PBL 3762A specifies the negative voltages in terms of voltage relative to the battery
supply voltage, VBAT
.
Tertiary protection is incorporated in the PBL 386 20/1 SLIC and the withstand is specified in terms of current
into this protection. This type of SLIC also has more time periods specified for the current withstand values.
To co-ordinate the SLIC external secondary protection (TISPPBL2S) and the internal tertiary protection, a
series resistor, RP, is required between the two. The tertiary protection will develop about 1 V and the
withstand current through resistor RP will also develop a voltage. The sum of these voltages will determine the
required limiting voltage level of the TISPPBL2S. A suitable value for RP is 2 Ω.
The negative limiting voltage of the TISPPBL2S is defined as a 1 µs, -20 V pulse below the battery voltage
(Figure 2). This value does not exceed any of the voltage withstand levels listed in the SLIC withstand table. In
the positive polarity the TISPBL2S limits the maximum voltage to 8 V in a 1 µs period and between 1 V and
5 V for a 10 ms period. These values do not exceed the values listed in the SLIC withstand table.
P R O D U C T
I N F O R M A T I O N
11
POINN [ POWER INNOVATIONS LTD ]
