cxa2640er Sony Electronics, cxa2640er Datasheet - Page 13

• Manufacturer Part Number: cxa2640er
• Description: 3-channel 2-ld Driver For Optical Disc Drive
• Manufacturer: Sony Electronics

Thermal resistance ( j-a) when mounted on PWB
• The thermal resistance ( c-a) is obtained by measuring the Package surface temperature using a thermo
• Diode thermal coefficient –2.27mV/°C and the positive protection diode thermal characteristics are used to
that are the reference, as described above are:
Thermal resistance ( j-a) is:
• Allowable power dissipation (P
• Maximum operating temperature
The V2 voltage found in (2) below cancels the voltage decrease caused by the wiring resistance between the
find this.
positive protection diode connection Vcc and the Vcc pins as reference and is measured to find the precise
temperature characteristics of the positive protection diode.
Tj using the voltage drop (V1 to V2) between the positive protection diode connection Vcc and the Vcc pins
couple or a radiation thermometer.
In order to improve the precision of measurement, it is desired to calculate by the following formula.
Assume the thermal resistance ( j-c) to be approximately 2°C/W.
Package surface temperature when Iop is variable/ Po
(1) V1 to OSCEN pin voltage to Vcc pin voltage, Icc1 to current consumption when 0V is applied to the
(2) V2 to OSCEN pin voltage to Vcc pin voltage immediately after applying the arbitrary voltage to the IINx
(3) V3 to OSCEN pin voltage to Vcc pin voltage, Icc3 to consumption current when applying the arbitrary
P
(150°C – Tj)
j-a = Tj/((Icc3 – Icc1)
IIN1, IIN2 and IIN3 pins.
pin.
voltage to the IINx pin and heat reaches equilibrium.
Tj = ((V3 + (V1 – V2)) – V1)/–2.27mV/°C
D
= (150°C – Ambient temperature)/ j-a
75°C
D
Vcc – Iop
)
P
O
[W]
Vop)
– 13 –
V
CC
OSCEN
V
CC
23
11
Pin voltage measurement
point
1M
GND
10V
5V
5V
5V
CXA2640ER