TB62208FNG
2011-01-28
14
IC Power Consumption
The power consumed by the TB62208FNG is approximately the sum of the following two: 1) the power consumed
by the output transistors, and 2) the power consumed by the logic and pre-drivers.
• The power consumed by the output transistors is calculated, using the R
ON(D–S)
value of 1.5 Ω.
Whether in Charge, Fast Decay or Slow Decay mode, two of the four transistors comprising each H-bridge
contribute to its power consumption at a given time.
Thus the power consumed by each H-bridge is given by:
P (out) = I
OUT
(A) × V
DS
(V) = 2 × I
OUT
2
× R
ON
..............................................(1)
In two-phase excitation mode (in which two phases have a phase difference of 90°), the average power
consumption in the output transistors is calculated as follows:
R
ON
= 1.50 Ω (＠1.0 A)
I
OUT
(Peak: max) = 1.0 A
V
M
= 24 V
P (out) = 2 × 1.0
2
(A) × 1.50 (Ω) = 3.0 (W)........................................................(2)
• The power consumption in the IM domain is calculated separately for normal operation and standby modes:
I (I
M3
) = 5.0 mA (typ.): Normal operation mode
I (I
M1
) = 2.0 mA (typ.): Standby mode
The current consumed in the logic portion of the TB62208FNG is indicated as IMx. The logic operates off a
voltage regulator that is internally connected to the VM power supply. It consists of the logic connected to V
M
(24 V)
and the network affected by the switching of the output transistors. The total power consumed by IMx can be
estimated as:
P (IM) = 24 (V) × 0.005 (A) = 0.12 (W)............................................................(3)
Hence, the total power consumption of the TB62208FNG is:
P = P (out) + P (IM) = 3.16 (W)
The standby power consumption is given by:
P (Standby) + P (out) = 24 (V) × 0.002 (A) = 0.048 (W)
Board design should be fully verified, taking thermal dissipation into consideration.
