TS3003
TS3003 Start-up Time
Using the TS3003 and a Potentiometer to Dim an
LED
As the TS3003 is powered up, its FOUT terminal
(and PWMOUT terminal, if enabled) is active once
the applied VDD is higher than 1.55V. Once the
applied VDD is higher than 1.55V, the master
oscillator achieves steady-state operation within 8ms.
The TS3003 can be configured to dim an LED by
modulating the pulse width of the PWMOUT output.
With an RSET= 2MΩ, the ꢀOꢁT output frequency is
approximately 51kHz (or 19.5µs period). Refer to
Figure 3. The CPWM capacitor was calculated using
Equation 2 with a pulse width of 15µs. To reduce the
pulse width from 15µs and in turn, dim the LED, a
1MΩ potentiometer is used. The potentiometer is
connected to the PWM_CNTRL pin in a voltage
divider configuration. The supply voltage of the circuit
is 5V.
Divide the PWMOUT Output Frequency by Two
with the TS3003
Using a single resistor and capacitor, the TS3003 can
be configured to a divide by two circuit as shown in
Figure 2. To achieve a divide by two function with the
TS3003, the pulse width of the PWMOUT output
must be at least a factor of 2 greater than the period
set at FOUT by resistor RSET. The CPWM capacitor
selected must meet this pulse width requirement and
can be calculated using Equation 2. In Figure 3, a
value of 4.32MΩ for RSꢇT sets the ꢀOꢁT output
period to 40µs. A CPWM capacitor of 265pF was
chosen, which sets the pulse width of PWMOUT to
approximately 80µs. This is well above the required
minimum pulse width of 40µs.
.
Figure 3: TS3003 Configured to Dim an LED with a
Potentiometer
Figure 2: Configuring the TS3003 into a Divide by
Two Frequency Divider
TS3003DS r1p0
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RTFDS
TOUCHSTONE [ TOUCHSTONE SEMICONDUCTOR INC ]
