Datasheet
Voltage Regulator
>
I
C
L-MIN
L
1 mA
1 µF
Supply Voltage Monitor
15 V
15 V
10 V
15 V > V24 > 10 V
18 V
18 V
V24
CHOK
1 ms
debounce
time starts
1 ms
debounce
time starts
Circuit ceases
operation
V24 < 10 V
t
DB-LH
t
DB-LH
t
DB-HL
Temperature Sensor
SN65HVS880
SLAS592C – MARCH 2008 – REVISED NOVEMBER 2008 ...............................................................................................................................................
www.ti.com
Table 2. Function Table
INPUTS
FUNCTION
LD CLK CE
L X X Parallel load
H X H No change
H ↑ L Shift
(1)
(1) Shift = content of each internal register shifts towards serial outputs.
Data at SIP is shifted into first register.
The on-chip linear voltage regulator provides a 5 V supply to the internal- and external circuitry, such as digital
isolators, with an output drive capability of 50 mA and a typical current limit of 115 mA. The regulator accepts
input voltages from 30 V down to 10 V. Because the regulator output is intended to supply external digital isolator
circuits proper output voltage decoupling is required. For best results connect a 1 µ F and a 0.1 µ F ceramic
capacitor as close as possible to the 5VOP-output. For longer traces between the SN65HVS880 and isolators of
the ISO72xx family use additional 0.1 µ F and 10 pF capacitors next to the isolator supply pins. Make sure,
however, that the total load capacitance does not exceed 4.7 µ F.
For good stability the voltage regulator requires a minimum load current, I
L-MIN
. Ensure that under any operating
condition the ratio of the minimum load current in mA to the total load capacitance in µ F is larger than 1:
The integrated supply voltage monitor senses the supply voltage of the SN65HVS880 at the V24-pin. If this
voltage drops below 15 V but stays within the regulator ’ s operating range, i.e., 15 V > V24 > 10 V, the output
CHOK goes low 1 ms later. When the supply voltage returns to 24 V, the CHOK output turns logic high after
6 ms. Should the supply voltage drop below 10 V, the device ceases operation. Upon the supply returning to
above 18 V, the CHOK output turns high again after 6 ms.
Figure 16. CHOK Output Timing as a Function of Supply Voltage Drop at V24
An on-chip temperature sensor monitors the device temperature and signals a fault condition if the device
becomes too hot. A first trip point exists at 150 ° C. If the junction temperature exceeds this trip point, the sensor
output, being active low, presents a low to the input of the AND gate forcing the CHOK output to go low. If the
junction temperature continues to rise, passing a second trip point at 170 ° C, all device outputs assume tri-state.
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