No. 5548-4/4

VPS13

VPS13 Thermal Design Example

Here we consider the case where this class of monitor is operated up to Ta = 60°C at a maximum clock frequency of

f = 130 MHz.

As mentioned previously, the chip with the largest loss is transistor 3 (Tr3) of the emitter-follower stage. Determining

that value gives:

Pc (emitter-follower stage) = 6.8

× 0.22 ≈ 1.5 [W] .....................(5)

Now, determine

∆Tj by substituting the value for

θj-c in equation (5).

∆Tj = 1.5 × 30 = 45 [°C]

Here,

∆Tj < 50°C, and we need only consider cases where Tc < 100 °C. Therefore, we must design a

θh for the heat sink

such that the Tc < 100°C condition holds when three channels are operating at maximum levels, i.e., Pd(TOTAL) =

Pd(one channel)

× 3.

∆Tc will be 100 – 60 = 40 °C, and therefore:

θh = ∆Tc ÷ Pd (TOTAL) = 40 ÷ (6.8 × 3) = 2.0, i.e. θh = 2.0 °C/W

In actual practice, the ambient temperature and operating conditions will allow a heat sink smaller than that indicated by

this calculation to be used. Therefore, design optimization taking the actual conditions and the above data into account is

also required.

This catalog provides information as of August, 1997. Specifications and information herein are subject to

change without notice.

s No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace

equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of

which may directly or indirectly cause injury, death or property loss.

s Anyone purchasing any products described or contained herein for an above-mentioned use shall:

distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all

damages, cost and expenses associated with such use:

SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees

jointly or severally.

s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for

volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied

regarding its use or any infringements of intellectual property rights or other rights of third parties.

80

10

40

45