67

of HIP5600 and the zener diode (

1N5243BPH)

(zener diode).

The regulator/zener diode configuration gives a 3.5%

(0.49/14.18) worst case output voltage error where, for the

same conditions, the regulator/resistor configuration results

in an 7.5% (1.129/15) worst case output voltage error.

External Capacitors

A minimum10

µF output capacitor (C2) is required for stability

of the output stage. Any increase of the load capacitance

greater than 10

µF will merely improve the loop stability and

output impedance.

A 0.02

ground may be required if the power source impedance is

not sufficiently low for the 1MHz - 10MHz band. Without this

capacitor, the HIP5600 can oscillate at 2.5MHz when driven

by a power source with a high impedance for the 1MHz -

10MHz band.

improves the ripple rejection by preventing the ripple at the

Adjust pin from being amplified. Bypass capacitors larger

than 10

µF do not appreciably improve the ripple rejection of

the part (see Figure 20 through Figure 25).

Load Regulation

For improved load regulation, resistor RF1 (connected

directly to the output of the regulator (Figure 4A) rather than

appearing effectively in series with RF1 and degrading regu-

lation. For example, a 15V regulator with a 0.05

Ω resistance

between the regulator and the load will have a load regula-

tion due to line resistance of 0.05

nected near the load the effective load regulation will be 11.9

times worse (1+R2/R1, where R2 = 12k, R1 = 1.1k).

FIGURE 4.

Protection Diodes

The HIP5600, unlike other voltage regulators, is internally

protected by input diodes in the event the input becomes

shorted to ground. Therefore, no external protection diode is

required between the input pin and the output pin to protect

against the output capacitor (C2) discharging through the

input to ground.

If the output is shorted in the absence of D1 (Figure 5), the

bypass capacitor voltage (C3) could exceed the absolute

maximum voltage rating of

Note; No protection diode (D1) is needed for output voltages

less than 6V or if C3 is not used.

FIGURE 5. REGULATOR WITH PROTECTION DIODE

Selecting the Right Heat Sink

Linear power supplies can dissipate a lot of power. This

power or heat must be safely dissipated to permit continuous

operation. This section will discuss thermal resistance and

show how to calculate heat sink requirements.

Electronic heat sinks are generally rated by their thermal

resistance. Thermal resistance is defined as the temperature

rise per unit of heat transfer or power dissipated, and is

expressed in units of degrees centigrade per watt. For a par-

ticular application determine the thermal resistance (

which the heat sink must have in order to maintain a junction

VREF VZ

+

=

(EQ. 3)

VOUT

∆

VTREF

VT

+

∆

=

(EQ. 4A)

VTREF

∆

∆

REFTC

Temp

∆

(

)

++

∆

≡

(EQ. 4B)

VTZ

∆

VZtolerance VZ

ZTC

Temp

∆

()

+

≡

(EQ. 4C)

Error Budget

+VREFTC θSA

OUT VIN

⋅

+

REFLINEREG

∆

AC/DC

AC/DC

(A)

(B)

RF1

RF2

HIP5600

AC/DC

RF1

RF2

HIP5600

AC/DC

RF1

RF2

C1

0.02

µF

C2

C3

10

µF

D1

D1 PROTECTS AGAINST C3

DISCHARGING WHEN THE

OUTPUT IS SHORTED.

HIP5600

10

µF

HIP5600