LA3246 Datasheet, PDF (7/13 Pages) Sanyo Semicon Device – Stereo Preamplifier for Compact Double Cassette Playback-only Use

LA3246
. _{Control circuit}
The control circuit for each CONT pin is configured as shown below. When a voltage more than a given value is applied,
the level on the pin is fixed by clamp diode D1.
Control pin
Current route
at clamp mode
Note: For D1, a Schottky diode is used for pin 9
and a silicon diode is used for pins 6, 15.
Unit (resistance: Ω, capacitance: F)
Description
. _{Switching level VSW of the control circuit is fixed by voltage V13 which is 1/2 of the voltage on pin 13.}
V_SW = 1/2 V13
. _{Clamp voltage VCLP at the time a voltage is applied to the CONT pin}
V_CLP = 1/2 × V13 + V_D1 + V_BE1
= 1/2 × V13 + 0.6 (0.3) + 0.6
where 0.9 V is for pin 9.
= 1/2 × V13 + (0.9 or 1.2)
1.2 V is for pins 6, 15.
. _{The maximum voltage at which the CONT pin is brought to GND level is fixed by the level at which the Q2 is completely}
turned OFF.
This level is:
1/2 × V13 – V_BE2 = 1/2 × V13 – 0.6 [V]
Switching is performed at a level less than this.
. _{To turn ON/OFF}
When turning ON:
To turn ON the control circuit to finish the
operation, I_B is required. Control voltage
V_OUT is obtained with I_B of 4 µA min.
. _{VCONT min = R × IB max + Operation finish voltage.}
I_B = 4 µA
Operation finish voltage
Pins 6, 15 : = 1/2 × V13
Pin 9 : = 1/2 × V13 + V_BE
. = 1/2 × V13 + 0.6 [V]
V_CONT max = R × I_B max + Clamp voltage
R is restricted by I_B max.
When the supply voltage is fixed, clamp voltage V_CLP is fixed. When resistor R is fixed based on a balance with capacitor C,
resistor R is restricted by V_CONT max. as shown below.
I_B max = 100 µA ^ ^{VCONT max – VCLP}
R
The minimum value of resistor R is fixed by this equation.
Example
Assuming V_CC = 10 V, V_CONT max = 10 V, Rmin is 50 kΩ.
Therefore, R = 100 kΩ presents no problem.
When turning OFF:
Bring the level on the CONT pin to a level less than:
1/2 × V13 – V_BE2 = 1/2 × V13 – 0.6 [V]
No.2651-7/13