Final Datasheet
May 23 2017
SWITCH CONTROL
The TS13101 CLK pin performs a dual function:
1. It provides the command sequences in level and timing that determine the state of the switch.
2. It provides a source of power by which the switch can operate.
The microcontroller provides the CLK signal to the switch by a coupling capacitor, C
ISO
, that provides galvanic
isolation between the microcontroller supply domain and that of the switch, the latter of which has a different
reference voltage with respect to ground dependent on its state. Because of the requirement to source power, it
is required that the microcontroller has a maximum source impedance of 100Ω.
The CLK pin is used as a means to command the state of the switch by the ON and OFF sequences shown in
Figure 2 through Figure 5. Figure 2 shows the state of the switch being changed by sending ON and OFF
Sequences. On initial power up, the switch state will default to the OFF condition.
It is necessary to send a device ON Sequence to transition the device to the ON state, as shown in Figure 3. First
a series of clocks, N
CLKON-INIT
, of frequency F
CLK
is transmitted, followed by a CLK low time of T
LOW-ON
. Then
another series of clocks of number N
CLKON
is transmitted. On the final CLK edge the switch will be closed. Note
that the CLK continues to cycle and the state of the DATA pin continues to be low. This indicates that the device
is ON.
When it is desired to transition the device to the OFF state, the OFF Sequence must be transmitted via the
microcontroller. This sequence is shown in Figure 4. Here the CLK is stopped for a period of T
CLKOFF-INIT
, followed
by a series of clocks of number N
CLKOFF
. Then the CLK must be asserted low for a period T
CLKOFF
, after which the
switch will be opened. If the CLK resumes switching, the DATA pin will return a signal F
CLK
/ 4, indicating that the
state of the switch is OFF.
Figure 5 shows the operation when an over-current event is detected, and the device autonomously transitions to
the OFF state in order to protect itself and the load in the system. During the ON time, the CLK was being
switched and the DATA pin was static, being held by the device in the low state. After the over-current event
opens the switch, the DATA pin will start switching at F
CLK
/ 4 to signal the microcontroller that the switch is no
longer in the ON state. The microcontroller may infer from this that there has been a fault in the system. If
diagnostics (performed elsewhere in the system) determine that the fault condition has been removed, the device
may be returned to the ON state through the restart sequence shown. After an over-current event opens the
switch, an OFF Sequence must be registered in the part before an ON Sequence can successfully transition the
device back to the ON state. The DATA pin will assert low and stay low after the ON Sequence as long as load
current remains below I
OUTOC
. If the switch transitions to the closed state and an over-current condition is
detected, the process of Figure 5 will repeat.
Failed Communication
In the event of a failed ON command sequence (due to external interference, system transients, etc.) the DATA
pin will begin sending a signal at frequency F
CLK
/ 4. Thus the microcontroller is alerted to a communication
failure. Similarly, when an OFF command sequence has been sent, resuming CLK pulses after the T
CLKOFF
time
will result in the DATA pin sending a signal of frequency F
CLK
/ 4. If the DATA pulses do not commence after 23
CLK cycles, the microcontroller can discern that the OFF sequence was not received correctly and the switch is
still in the closed state. It is up to the microcontroller to do this fault handling and rectify the situation.
