ROHM BA6819AF, BA6809F Datasheet

Motor driver ICs

2-phase half-wave motor driver

BA6809F / BA6819AF

The BA6809F and BA6819AF are motor drivers designed for 3V and 5V fan motors. Built-in output transistors reduce
the number of external components required. The ICs have an alarm output pin (BA6809F) and Hall output pin
(BA6819AF).

Applications
Fan motors

Features

1) Lock detection and rotational speed sensing mecha­nisms are built in.

2) Alarm output pin (BA6809F) and Hall output pin
(BA6819AF).

Absolute maximum ratings (Ta = 25C)

3) Built-in thermal shutdown circuit.

4) Operation assured with a supply voltage as low as

2.7V.

5) Compact 8-pin SOP package.

Recommended operating conditions (Ta = 25C)

706

Motor driver ICs BA6809F / BA6819AF

Block diagram

Pin descriptions

Hall input / output truth table

707

Motor driver ICs BA6809F / BA6819AF

Input / output circuits

Electrical characteristics (unless otherwise noted, Ta = 25C and V

708

CC = 3V)

Motor driver ICs BA6809F / BA6819AF

FCircuit operation
The BA6809F and BA6819AF have motor lock detection
and automatic restart circuits. The timing of lock detec­tion and automatic restart is determined by the external
capacitor connected to the LD pin. The charge time of the
external capacitor is given by :

C S (V

C S (V

LDCLVLDCP)

I

LDC

LDCLVLDCP)

ILDD

ton (Charge time)=

toff (Discharge time)=

where
V

LDCL is the LD-pin clamp voltage (1.90V),
LDCP is the LD-pin comparator voltage (0.73V),

V

LDC is the LD-pin charge current (2.2µA),

I

LDD is the LD-pin discharge current (0.42µA),

I
C is the capacitance of the LD-pin external capacitor.
For C=0.47µF, for example, the charge and discharge
times are 0.25s (output ON) and 1.31s (output OFF), re­spectively .

(Typical value)

FApplication example

709

Motor driver ICs BA6809F / BA6819AF

Operation notes
(1) Thermal shutdown circuit
The IC has a built-in thermal shutdown circuit. The is a
temperature difference of 20C (typical) between the
temperatures at which the circuit is activated and deacti­vated.

The circuit is activated at the temperature of about 175C
(typical), so that all outputs are turned OFF. Normal op­eration resumes when the circuit is deactivated.

(2) Power dissipation
Power consumed in the IC can be calculated from the fol­lowing equation :

P

C=PC1)PC2)PC3

PC1 is power consumed by the circuit current.

C1=VCC ICC

P

PC2 is the output current consumption.

C2=VOL IO

P

VOL is the LOW level output voltage of output pins
1 and 2, and I

C3 is power consumed by the AL and HO pins.

P

C3=VALL IAL (BA6809F)

P
P

C3=VHOL IHO / 2 (BA6819AF)

O is the sink current of pins 1 and 2.

where

ALL is the AL-pin LOW level voltage,

V

AL is the AL-pin sink current,

I

HOL is the HO-pin LOW level voltage,

V
I

HO is the HO-pin sink current.

Make sure that your application does not exceed the al­lowable power dissipation of the IC.

(3) Hall amplifier input voltage

The R1 and R2 resistances must be set so as to maintain
the Hall amplifier input bias voltage within the range of 0V

CC*2V) including the signal amplitude.

to (V
The Hall device may be affected by power supply noise
due to the PCB conductor pattern. If you have this prob­lem, insert a capacitor C1 as shown in Fig. 5.
If the conductor lines from the Hall device output termi­nals to the Hall inputs of the IC are particularly long, noise
can be picked up and fed into the inputs. If you have this
problem, insert a capacitor C2 as shown in Fig. 5. Note
that the Hall inputs have no hysteresis in this IC.

V

Hall current is given by=

CC

R1)R2)RH

where RH is the Hall device impedance.

710

Motor driver ICs BA6809F / BA6819AF

External dimensions (Units: mm)

711