IC-DC_17 Datasheet, PDF (11/19 Pages) IC-Haus GmbH – 2-CHANNEL BUCK/BOOST DC/DC CONVERTER

iC-DC
2-CHANNEL BUCK/BOOST DC/DC CONVERTER
DESCRIPTION OF FUNCTIONS
Rev B1, Page 11/19
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.
S4 ^VH
VB ^D1 VBR _S1 VBL _LVBH VHL
S3
S2
S5 ^VH1
S6 ^VH2
CVH
RVH
CVH1
RVH1
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.
CVH2
RVH2
Figure 1: Principle of operation of the converter
Dual 3.3V/5V BOOST/BUCK SMPS, 05.05.2008 11:51:33
400mA
300mA
200mA
100mA
0
I(LVBH)
4V
3V
2V
1V
0
-1V
V(VBL)
8V
6V
4V
2V
0
V(VHL)
8.887ms
8.888ms
Time (linear) [Plot 0]
8.889ms
8.89ms
Figure 2: Converter current/voltage characteristics (VB = 4 V)