TLC5905

LED DRIVER

SLLS401 – NOVEMBER 1999

17

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

OVM (output voltage monitor) function (continued)

output signal check for XDOWN1, XDOWN2

XDOWN1 or XDOWN2 can be forced to a low level by setting the appropriate latch value for OVM. This allows

investigation of the correct connection of XDOWN1 or XDOWN2 to the external system. Since both XDOWN1

and XDOWN2 terminal are open-collector outputs, outputs of multiple ICs are brought together.

OVM comparator setting

Setting the OVM latch is shown in Table 5. Note that the comparison voltage is set to the default value of 0.3 V

when MCENA tied to a low level.

Table 5. OVM Setting

MONITOR CONTROL DATA

COMPARISON

XDOWN1

XDOWN2

MSB

LSB

VOLTAGE

XDOWN1

XDOWN2

0000

NO COMPARISON

DEPEND ON TSD/WDT

HI–Z

0001†

0.3 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0010

0.4 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0011

0.5 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0100

0.6 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0101

0.7 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0110

0.8 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

0111

0.9 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1000

1.0 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1001

1.1 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1010

1.2 V

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1011

1/3

× VCC(ANA)

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1100

1/2

× VCC(ANA)

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1101

2/3

× VCC(ANA)

DEPEND ON TSD/WDT

DEPEND ON OVM COMPARATOR

1110

0.3 V

L

DEPEND ON OVM COMPARATOR

1111

0.3 V

DEPEND ON TSD/WDT

L

† MCENA is low.

SOUT output timing selection

The timing for the SOUT output can be switched by selecting the SOMODE level. When SOMODE is low, SOUT

is clocked out synchronizing to the rising edge of SCLK. When SOMODE is high, SOUT is clocked out

synchronizing to the falling edge of SCLK. When the shift operation with SOMODE high, data can be protected

from shift error even if the SCLK signal is buffered in serial externally. In this case, when ICs are connected in

cascade, the maximum data transfer speed will be slower than the case of SOMODE low.

protection

This device incorporates WDT and TSD functions. If the WDT or TSD is turned on, then the constant current

output is stopped and XDOWN1 goes low. Therefore, by monitoring XDOWN1 terminal, these failures can be

detected immediately. Since the XDOWN1 output is configured as an open collector, outputs of multiple ICs are

brought together.