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MM1538XQ

4-ch Motor Driver for Portable CD Players

Mitsumi 

MITSUMI

4ch Moter driver IC for Portable CD Player

(5) Over voltage protection circuit

· When the voltage applied to BSEN(1PIN)reaches 8.4V typ. , SPRT(8PIN)is charged, and when the voltage

reaches 1.2V typ. , theSW(5PIN)switching stops. The time until switching stops is set by the capacitor

connected to SPRT(8PIN)according to the following formula.

t=CSPRT VTH (sec) (VTH=1.2V, IHV=20µA)

IHV

4 Empty detector block

(1) Output voltage

· When the voltage applied to the BSEN(1PIN)falls below the detector voltage, EMP(35PIN)goes from high

level to low level(open-collector output). The detector voltage has 50mV typ. of hysteresis to prevent

output chattering. Use SEL(42PIN)to switch the detection voltage as shown below.

SEL

L

High-Z

Detect Voltage

2.20V typ.

1.80V typ.

Return Voltage

2.25V typ.

1.85V typ.

5 Reset circuit block

· At about 90% typ. of the DC-DC converter output voltage, RESET(3PIN)goes from low level to high level,

and AMUTE(34PIN)goes from high level to low level. The reset voltage has 50mV typ. of hysteresis to

prevent output chattering.

6 Charging circuit block

· The power supply for the charging circuit block is CHGVCC(41PIN), and is independent from the other

circuits.The resistance between RCHG(33PIN)and GND sets the charging current. This current is drawn

from SEL(42PIN).

· A thermal shutdown circuit is provided,and when the chip temperature reaches 150°C typ. the charging

current is cut. The chip starts operating again at about 120°C typ. .

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