IC-DC datasheet(13/19 Pages) ICHAUS

13 / 19 page

iC-DC

2-CHANNEL BUCK/BOOST DC/DC CONVERTER

Rev B1, Page 13/19

LINEAR REGULATORS VCC1 AND VCC2

To achieve as low an interference voltage as possible,

even with small filter capacitors CVH1 and CVH2, an in-

dependent linear regulator is connected after each of

the intermediate voltages VH1 and VH2.

Output voltages VCC1 and VCC2 can each be adjusted

using a voltage divider at CFG1 and CFG2 within a

range of 1.5 to 5.5 V ±5 % and according to Equations

1 and 2.

VVCC1 = V(RREF) × (1 +

)

(1)

and

VVCC2 = V(RREF) × (1 +

)

(2)

NB: R1 + R2 and R3 + R4 = 10 kΩ up to 50 kΩ

V(RREF) Electrical Characteristics 401

Inputs CFG1 and CFG2 can also be directly connected

to the relevant output voltage VCCx or GNDA. The

resulting voltages are given in Tables 4 and 5.

VCC1 output voltage

Potential at CFG1

VCC1

GNDA

3.3 V

VCC1

5.0 V

Voltage divider

1.5 V to 5.5 V

Table 4: VCC1 settings

VCC2 output voltage

Potential at CFG2

VCC2

GNDA

2.5 V

VCC2

3.3 V

Voltage divider

1.5 V to 5.5 V

Table 5: VCC2 settings

The regulators have been compensated internally so

that they are stable in no-load operation without an ex-

ternal capacitor. Stability across the entire load range

is guaranteed by the minimum capacitances for CVCC1

and CVCC2 given in the electrical characteristics. The

outputs are current limited to protect them against de-

struction in the event of a short circuit.

The two linear regulators can be switched on and off

independently by inputs ENV1 and ENV2. If both regu-

lators are deactivated, iC-DC is in standby mode (see

DESCRIPTION OF FUNCTIONS/Standby).

Switched output voltages

The two pins POE1 and POE2 are triggered by monitor

outputs V1OK and V2OK and provide voltages drawn

from VCC1 or VCC2. This enables the supply of spe-

cific circuitry in a component group (e.g. EEPROMs) to

be switched on only after VCC1 or VCC2 have reached

their steady state.

Voltage monitor self-test

Using pin TEST the voltage monitoring comparators at

V1OK and V2OK can be tested during ongoing opera-

tion. The undervoltage and overvoltage thresholds of

V1OK and V2OK are checked in turn with each test.

For this purpose, pin TEST is increased to above the

threshold voltage by an external driver. Correct func-

tioning is signaled by low signals at pins V1OK and

V2OK. The function of the connected POE1 and POE2

outputs remains unaffected.

Current carrying capacity

iC-DC’s current carrying capacity depends on set out-

put voltage VCCx and input voltage VB. Figure 4 shows

the current carrying capacity dependent on the input

voltage for various output voltages, measured on the

iC-DC EVAL DC1D evaluation board. The internal re-

verse polarity protective circuit was bridged (VB = VBR)

to increase the current carrying capacity.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

100

150

200

250

300

350

400

450

500

VH (>7.2V)

5V VCCx

3,3V VCCx

2,5V VCCx

1,5V VCCx

Input Voltage VB [V]

Figure 4: Current carrying capacity for various out-

put voltages dependent on VB (VB = VBR)

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