IC-DC datasheet(11/19 Pages) ICHAUS

11 / 19 page

iC-DC

2-CHANNEL BUCK/BOOST DC/DC CONVERTER

Rev B1, Page 11/19

DESCRIPTION OF FUNCTIONS

DC/DC converter iC-DC generates two regulated volt-

ages of VH1 and VH2 from voltage VBR. These pre-sta-

bilize the two linear regulators VCC1 and VCC2. A

third voltage of VH, also regulated, is generated to

drive these linear regulators. Voltage supply VB may

be either above or below the output voltages. Figure 1

shoes the basic function principle of iC-DC. Switches

S1 to S6 and diode D1 have been implemented on the

chip. The inductor, capacitors, and load resistors are

external devices.

RVH2

CVH2

RVH

RVH1

CVH

CVH1

VH1

VH2

VHL

VBR

VBL

LVBH

CVH

CVH1

CVH2

RVH

RVH1

RVH2

Figure 1: Principle of operation of the converter

Another feature of iC-DC is that bias voltages VH1 and

VH2 adjust themselves automatically to approximately

400 mV using the selected VCC1 or VCC2 voltage. This

results in minimum power dissipation as only a low

amount of voltage is lost through each of the linear

regulators.

Charge/discharge phase

During the charge phase switches S1 and S2 close with

the internal clock. A linearly increasing current flows

through coil LVBH. The energy from supply VBR is

stored in the coil’s magnetic field.

Switches S1 and S2 open for discharging. Switch S3

and one of the switches S4/S5/S6 are closed. The cur-

rent can continue to flow in the coil and is supplied to

the relevant capacitor and relevant load. Figure 2 de-

scribes the resulting course of the current and voltage.

The current rise and fall times depend on the inductor

voltage.

Dual 3.3V/5V BOOST/BUCK SMPS, 05.05.2008 11:51:33

V(VHL)

8.887ms

8.888ms

8.889ms

8.89ms

Time (linear) [Plot 0]

V(VBL)

-1V

I(LVBH)

100mA

200mA

300mA

400mA

Figure 2: Converter current/voltage characteristics (VB = 4 V)

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