TS3002 TOUCHSTONE [Touchstone Semiconductor Inc], TS3002 Datasheet - Page 9

• Manufacturer Part Number: TS3002
• Description: A 1V/1uA Easy-to-Use Silicon Oscillator/Timer
• Manufacturer: TOUCHSTONE [Touchstone Semiconductor Inc]

the CNTRL both enables the TS3002’s internal PWM
engine as well as adjusting the duty cycle from 12%
to 90%. A dc control voltage equal to 0.03 x VDD
applied to the CNTRL pin enables the PWM engine
to set the duty cycle to 12%. A dc control voltage
equal to 0.27 x VDD increases the duty cycle to 90%
and connecting CNTRL to VDD disables the PWM
engine altogether. Configured for nominal operation
(PWM engine OFF, BOOST pin to GND), the supply
current of the TS3002 is 1µA; enabling the PWM
engine increases the TS3002 operating supply
current as shown in the electrical specification table.
The BOOST pin controls the propagation delay of the
TS3002’s internal comparators. When BOOST is
connected
programmable
Connecting the BOOST pin to VDD reduces the
propagation delay of the internal oscillators, thereby
extending
frequency to 290kHz.
APPLICATIONS INFORMATION
Minimizing Power Consumption
To keep the TS3002’s power consumption low,
resistive loads at the FOUT and PWMOUT terminals
increase dc power consumption and therefore should
be as large as possible. Capacitive loads at the
FOUT
TS3002’s transient power consumption and, as well,
should be as small as possible.
One challenge to minimizing the TS3002’s transient
power consumption is the probe capacitance of
oscilloscopes and frequency counter instruments.
Most instruments exhibit an input capacitance of
15pF or more. Unless buffered, the increase in
transient load current can be as much as 400nA.
To minimize capacitive loading, the technique shown
in Figure 1 can be used. In this circuit, the principle of
series-connected capacitors can be used to reduce
TS3002DS r1p0
Figure 1: Using an External Capacitor in Series with
and
Probes Reduces Effective Capacitive Load.
the
to
PWMOUT
operating
GND,
high
end
the
terminals
frequency
TS3002’s
maximum
increase
is
maximum
operating
~90kHz.
the
the effective capacitive load at the TS3002’s FOUT
and PWMOUT terminals.
To determine the optimal value for C
probe capacitance is known by simply solving for
C
For example, if the instrument’s input probe
capacitance is 15pF and the desired effective load
capacitance at either or both FOUT and PWMOUT
terminals is to be ≤5pF, then the value of C
be ≤7.5pF.
TS3002 Start-up Time
As the TS3002 is powered up, its FOUT terminal
(and PWMOUT terminal, if enabled) is active once
the applied VDD is higher than 0.9 volt. Once the
applied VDD is higher than 0.9 volt, the master
oscillator achieves steady-state operation within
1.2ms.
Current- and Voltage-Controlled Oscillators
The TS3002 can be configured into a Current-
Controlled Oscillator as shown in Figure 2. With a
current source sourcing a current of 223nA to 262nA,
FOUT can generate an output signal with a frequency
range of 5.2kHz to 90kHz. In a similar manner, a
Voltage-Controlled Oscillator can be configured as
shown in Figure 3. In this case, a voltage source
sourcing a voltage of 290mV to 341mV can generate
an FOUT output signal frequency range of 5.2kHz to
90kHz as well. It is recommended to use resistor
values with a 1% tolerance.
EXT
Figure 2: Configuring the TS3002 into a
using the following expression:
C
Current-Controlled Oscillator.
E T
=
C
LOAD(EFF)
1
1
C
TS3002
PROBE
1
EXT
once the
EXT
Page 9
should
RTFDS