MC33102 Datasheet, PDF (12/14 Pages) ON Semiconductor – DUAL SLEEP-MODE OPERATIONAL AMPLIFIER

MC33102
The transition time (ttr1) required to switch from sleep to
awake mode is:
ttr1 = tD = ITH (RL/SRsleepmode)
Where: tD = Amplifier delay (<1.0 µs)
ITH = Output threshold current for
= more transition (160 µA)
RL = Load resistance
SRsleepmode = Sleepmode slew rate (0.16 V/µs)
Although typically 160 µA, ITH varies with supply voltage
and temperature. In general, any current loading on the
output which causes a current greater than ITH to flow will
switch the amplifier into the awakemode. This includes
transition currents such as those generated by charging load
capacitances. In fact, the maximum capacitance that can be
driven while attempting to remain in the sleepmode is
approximately 1000 pF.
CL(max) = ITH/SRsleepmode
= 160 µA/(0.16 V/µs)
= 1000 pF
Any electrical noise seen at the output of the MC33102
may also cause the device to transition to the awakemode. To
minimize this problem, a resistor may be added in series with
the output of the device (inserted as close to the device as
possible) to isolate the op amp from both parasitic and load
capacitance.
The awakemode to sleepmode transition time is controlled
by an internal delay circuit, which is necessary to prevent the
amplifier from going to sleep during every zero crossing. This
time is a function of supply voltage and temperature as
shown in Figure 22.
Gain bandwidth product (GBW) in both modes is an
important system design consideration when using a
sleepmode amplifier. The amplifier has been designed to
obtain the maximum GBW in both modes. “Smooth” AC
transitions between modes with no noticeable change in the
amplitude of the output voltage waveform will occur as long
as the closed loop gains (ACL) in both modes are
substantially equal at the frequency of operation. For smooth
AC transitions:
(ACLsleepmode) (BW) < GBWsleepmode
Where: ACLsleepmode = Closed loop gain in
ACLsleepmode = the sleepmode
BW = The required system bandwidth
BW = or operating frequency
TESTING INFORMATION
To determine if the MC33102 is in the awakemode or the
sleepmode, the power supply currents (ID+ and ID–) must be
measured. When the magnitude of either power supply
current exceeds 400 µA, the device is in the awakemode.
When the magnitudes of both supply currents are less than
400 µA, the device is in the sleepmode. Since the total supply
current is typically ten times higher in the awakemode than
the sleepmode, the two states are easily distinguishable.
The measured value of ID+ equals the ID of both devices
(for a dual op amp) plus the output source current of device A
and the output source current of device B. Similarly, the
measured value of ID– is equal to the ID– of both devices plus
the output sink current of each device. Iout is the sum
of the currents caused by both the feedback loop and load
resistance. The total Iout needs to be subtracted from the
measured ID to obtain the correct ID of the dual op amp.
An accurate way to measure the awakemode Iout current
on automatic test equipment is to remove the Iout current on
both Channel A and B. Then measure the ID values before
the device goes back to the sleepmode state. The transition
will take typically 1.5 seconds with ±15 V power supplies.
The large signal sleepmode testing in the characterization
was accomplished with a 1.0 MΩ load resistor which ensured
the device would remain in sleepmode despite large
voltage swings.
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MOTOROLA ANALOG IC DEVICE DATA