3. Functional Description
3.1 Device Behavior
Truth tables for the Si873x are summarized in the table below.
Table 3.1. Si873x Truth Table Summary
Input Enable Output
Si8735 (Non-inverting)
OFF N/A LOW
ON N/A HIGH
Si8736 (Inverting)
OFF HIGH HIGH
ON HIGH LOW
X LOW HIGH
Note: This truth table assumes VDD is powered (VDD> UVLO). If VDD is below UVLO, see 3.3
Under Voltage Lockout (UVLO) for
more information. When VDD < UVLO, the output state is not guaranteed. In this condition, the output level is determined by external
circuity connected to the output.
3.2 Device Startup
During startup-up, for the Si873x, Output V
O
is high until V
DD
rises above the UVLO+ threshold for a minimum time period of t
START
.
Following this, the output is low when the current flowing from anode to cathode is > I
F(ON)
. Device startup, normal operation, and shut-
down behavior for the Si873x is shown in the figure below. Note that the figure below assumes that Enable is asserted and that the
outputs are operating in their normal operating condition (inverting for the Si8736). See the table above for more details on the Enable
function.
I
F
V
O
V
DD
t
START
t
PLH
t
PHL
I
F(ON)
I
HYS
UVLO+
t
PLH
VDD
HYS
UVLO-
t
ST
AR
T
Figure 3.1. Si8736 Operating Behavior (I
F
> I
F(MIN)
when V
F
> V
F(MIN)
)
Si873x Data Sheet
Functional Description
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