bd67929efv ROHM Co. Ltd., bd67929efv Datasheet - Page 10

• Manufacturer Part Number: bd67929efv
• Description: Three-phase Brushless Motor Driver For Polygonal Mirrors [for Lbp, Ppc]
• Manufacturer: ROHM Co. Ltd.

●Power Consumption
BD67929EFV
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
Please confirm that the IC's chip temperature Tj is not over 150℃, while considering the IC's power consumption (W),
package power (Pd) and ambient temperature (Ta). When Tj is exceeded 150℃, the functions as a semiconductor do not
operate and problems such as parasitism and leaks occur. Constant use under these circumstances leads to deterioration
and eventually destruction of the IC. Tjmax=150℃ must be strictly obeyed under all circumstances.
○Thermal Calculation
○Temperature Monitoring
The IC's consumed power can be estimated roughly with the power supply voltage (VCC), circuit current (ICC),
output ON resistance (R
Consumed power of the Vcc [W] = V
Consumed power of the output DMOS [W] = (R
However, the thermal resistance valueθ
derating curve on P.10. Also, we are taking measurements of thermal resistance valueθ
Please feel free to contact our salesman. The calculated values above are only theoretical. For actual thermal design,
please perform sufficient thermal evaluation for the application board used, and create the thermal design with enough
margin to not exceed Tjmax=150℃. Although unnecessary with normal use, if the IC is to be used under especially strict
heat conditions, please consider externally attaching a Schottky diode between the motor output terminal and GND to
abate heat from the IC.
There is a way to directly measure the approximate chip temperature by using the TEST terminal. However, temperature
monitor using this TEST terminal is only for evaluation and experimenting, and must not be used in actual usage
conditions. TEST terminal has a protection diode for prevention from electrostatic discharge. The temperature may be
monitored using this protection diode.
V
(1) Measure the terminal voltage when a current of Idiode=50µA flows from the TEST terminal to the GND, without
(2) Measure the temperature characteristics of this terminal voltage. (Vf has a linear negative temperature may be
(3) Supply VCC, confirm the TEST terminal voltage while running the motor, and the chip temperature can be
t
Please confirm by actual measurement, or make an approximate calculation.
t
High side Pch DMOS ON Resistance R
Low side Nch DMOS ON Resistance R
on
chop
supplying VCC to the IC. This measurement is of the Vf voltage inside the diode.
calibrated from the TEST terminal voltage.
approximated from the results of (2).
TEST
varies depending on the L and R values of the motor coil and the current set value.
is the period of chopping which is set by the external capacitor of OSC terminal. See page 5 for detail.
Consumed power of total IC W_total[W] = ① + ②
Junction temperature Tj = Ta[℃] + θja[℃/W]･W_total [W]
Idiode
Circuitry
ONH
VCC
, R
ONL
) and motor output current value (I
Model diagram for measuring chip temperature
CC
Circuitry
[V] × I
ja
ONL
ONH
[℃/W] differs greatly depending on circuit board conditions. Refer to the
CC
ONH
[Ω] (typ.)= 0.65 [Ω]
[Ω] (typ.)= 0.70 [Ω]
[A] ･･･････①
+ R
-Vf[mV]
10/14
ONL
)×I
OUT
2
×on_duty +{R
25
OUT
).
ONL
×I
OUT
150
2
+D
ja
IVL
of boards actually in use.
×I
T
j
[℃]
OUT
Technical Note
2010.12 - Rev.A
}(1-on_duty) ･･･②