AP1158ADS Datasheet, PDF (20/24 Pages) Asahi Kasei Microsystems – Active Noise Filter IC

[AP1158ADS]
12. Definition of Term
・Sink Current of FIL Terminal
The sink current of the FIL terminal is 0.6A(typ). The Vdrop is calculated as follows.
Vdrop = {(Sink Current)  (Rfil)} + (Offset voltage)
Ripple rejection ratio largely depends on this value.
Standard value: Rfil = 390kΩ (Vdrop =270mV) , Vdrop (mV) = Rfil (k) × 0.6A + 40mV
·Input-output voltage drop (Vdrop)
Vdrop is set by Rfil. It is necessary to set Vdrop large when there is a margin between the input voltage and
output voltage, or the ripple noise is large. Please fix the Vdrop according to ripple noise, maximum output
current and operating voltage.
· On / Off Control
Control terminal is active “H”. By connecting the terminal to GND, input current becomes almost zero.
(Operation stops) If the load current is 0 (the load impedance is very high), the Cout electric charge remains.
Therefore, if the ripple filter IC is switched at the same time with the load, quick response application will be
available. In case not using on/off control, please connect this terminal to Vin. The control current decreases
when resistance is connected in series. Series resistance around 300kΩ and pull-down resistor are built in this
terminal. Therefore, when series resistance is connected, the control current will decrease though the control
voltage may swerves to high side. There is no hysteresis in this terminal. Please apply “H” or “L” surely
otherwise noise level will increase.
·Ripple Rejection Ratio (R.R.)
Ripple rejection is the ability of the IC to attenuate the ripple content of the input voltage at the output. It is
specified with the input voltage with AC voltage (condition: 1) overlapped with DC voltage (condition: 2)
Condition1: 200mVp-p, f=1kHz, Condition2: Vin=2.5V
The measurement condition is as follows.
Cin=0.1F, Cout=1F, Cfil=4.7F, Rfil=390kΩ(Vdrop=270mV),Vin: DC=2.5V, AC=200mVp-p (at f=1kHz)
It is necessary to enlarge Rfil and Cfil to improve the ripple rejection ratio at the low frequency range. The
ripple rejection depends on the set Vdrop and the characteristics of the capacitor. Please consider the tolerance
of resistor and capacitor. Please adjust the value of Rfil(=390kΩ) and Cfil(=4.7μF) depends on application.
· On / Off speed
Vout rises at high-speed when Cont pin is controlled with the input voltage is added to Vin pin. Operation will
be very slow when the power supply is started by other control functions. When the time constant of the filter
is small, Vout stands up quickly. By connecting diode in parallel with Rfil, Vout also stands up quickly.
·Maximum Output Current (Iout MAX)
The rated output current is specified under the condition when the output voltage drops 10% the value
specified with Iout=5mA. The input voltage is set at VoutTYP+1V and the current is pulsed to minimize
temperature effect.
·Reverse Bias Current (Irev)
The current flows from the Vout pin to the IC when Vin=0V, Vcont=0V and Vout=8V.
·Quiescent Current (Ignd)
The current flows to GND terminal. It is the difference between the input current and the output current.
015006896-E-00
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2015/05