iC-DC
2-CHANNEL BUCK/BOOST DC/DC CONVERTER
Rev A3, Page 11/19
DESCRIPTION OF FUNCTIONS
DC/DC converter iC-DC generates two regulated volt- Another feature of iC-DC is that bias voltages VH1 and
ages of VH1 and VH2 from voltage VBR. These presta- VH2 adjust themselves automatically to approximately
bilize the two linear regulators VCC1 and VCC2. A 400 mV using the selected VCC1 or VCC2 voltage.
third voltage of VH, also regulated, is generated to This results in minimum power dissipation as only a
drive these linear regulators. Voltage supply VB may low amount of voltage is lost through each of the linear
be either above or below the output voltages. Figure 1 regulators.
shoes the basic function principle of iC-DC. Switches
S1 to S6 and diode D1 have been implemented on the Charge/discharge phase
chip. The inductor, capacitors, and load resistors are During the charge phase switches S1 and S2 close
external devices.
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.
VH
VH1
VH2
S4
S5
S6
CVH
RVH
D1
VB
VBR
VBL
VHL
LVBH
S1
CVH1
CVH2
RVH1
RVH2
S3
S2
Figure 1: Principle of operation of the converter
400mA
300mA
200mA
100mA
0
I(LVBH)
4V
3V
2V
1V
0
-1V
V(VBL)
8V
6V
4V
2V
0
8.887ms
8.888ms
8.889ms
8.89ms
Time (linear) [Plot 0]
V(VHL)
Figure 2: Converter current/voltage characteristics (VB = 4 V)
ICHAUS [ IC-HAUS GMBH ]
