IC-DC IC-Haus, IC-DC Datasheet - Page 14

• Manufacturer Part Number: IC-DC
• Description: 2-CHANNEL BUCK/BOOST DC/DC CONVERTER
• Manufacturer: IC-Haus

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R1
R2
VCC1
A protective switch inserted between supply VB and
pin VBR protects the entire system against reverse po-
larity. This can also be used to implement an Autarky
function (see AUTARKY FUNCTION). By connecting
VB to VBR the reverse polarity protection circuit can be
bridged to improve the current carrying capacity and
the overall efficiency, especially if low supply voltages
are used (Figure 5).
The reverse polarity protection switch is current lim-
ited to the maximum mean current consumption of the
system (Electrical Characteristics 104). A capacitor
(CVBR) must be connected to pin VBR if higher coil
cut-off currents are to be supplied.
This capacitor should have a value of at least 1 µF at
a supply voltage of VB = 24 V (Figure 6). With very
small supply voltages the value must be greater in or-
der to cater for the higher power consumption during
startup. The voltage at VBR must no longer drop below
the lower shutdown threshold (Electrical Characteris-
tics 202) to ensure safe converter startup. A capacitor
of approx. 10 µF should thus be selected for CVBR at
a supply voltage of VB = 4 V (Figure 7).
REVERSE POLARITY PROTECTION
iC-DC
2-CHANNEL BUCK/BOOST DC/DC CONVERTER
Figure 5: Protection against reverse polarity bridges
RREF
RREF
4...36V
20k
20k
R3
R4
VCC2
CVB
CVB
VB to VBR
1μF
1μF
VBROK
TOK
RREF
ENV1
ENV2
CFG1
CFG2
NAUT
ERROR DETECT.
OSCILLATOR
REFERENCE
OUTPUT
ENABLE
CONFIGURATION
VCC1:
5V/3.3V/R1:R2
VCC2:
3.3V/2.5V/R3:R4
VB
REVERSE
PROTECT.
INTERNAL
SUPPLY
BIAS
SHUTDOWN
AUTARKY
DETECT.
THERMAL
VOLTAGE
MONITOR
VBR
SWITCHING REGULATOR
CONTROL
BOOST
BUCK
GNDA
iC-DC
22μH
22μH
LVBH
LVBH
VBL
GND
VHL
R1
R2
R1
R2
VCC1
VCC1
It is possible to use the protective switch at pin VBR
to provide further circuitry with protection against re-
verse polarity (Figure 9, Page 17). Here, it must noted
that the current carrying capacity of the reverse polar-
ity protection (VBR) is limited on startup. As the device
powers itself from VBR, the load at VBR must not be
too high as otherwise converter operation cannot be
initiated. The current carrying capacity on startup can
be approximately described by Equation 3:
Figure 6: Protection against reverse polarity active,
Figure 7: Protection against reverse polarity active,
RREF
RREF
RREF
RREF
20k
20k
20k
20k
24V
R3
R3
R4
R4
1
2
4V
VCC2
VCC2
TEST
LIN.-REG.2
LIN.-REG.1
CVB
CVB
CVB
CVB
VCC1,VCC2
CVBR for VB = 24 V
CVBR for VB = 4 V
1μF
1μF
VBROK
1μF
1μF
VBROK
TOK
RREF
ENV1
ENV2
CFG1
CFG2
TOK
RREF
ENV1
ENV2
CFG1
CFG2
NAUT
NAUT
I(VBR) = V (VB)
ERROR DETECT.
ERROR DETECT.
MONITORING
OSCILLATOR
OSCILLATOR
REFERENCE
OUTPUT
ENABLE
CONFIGURATION
VCC1:
5V/3.3V/R1:R2
VCC2:
3.3V/2.5V/R3:R4
REFERENCE
OUTPUT
ENABLE
CONFIGURATION
VCC1:
5V/3.3V/R1:R2
VCC2:
3.3V/2.5V/R3:R4
VB
VB
VOLTAGE
REVERSE
PROTECT.
INTERNAL
SUPPLY
REVERSE
PROTECT.
INTERNAL
SUPPLY
BIAS
BIAS
SHUTDOWN
SHUTDOWN
AUTARKY
DETECT.
THERMAL
AUTARKY
DETECT.
THERMAL
VOLTAGE
MONITOR
VOLTAGE
MONITOR
CVBR
CVBR
CVBR
CVBR
&
&
10μF
10μF
1
2
1μF
1μF
SUPPLY
SWITCH 1
SUPPLY
SWITCH 2
2
1
Rev A3, Page 14/19
1mA
VBR
VBR
SWITCHING REGULATOR
SWITCHING REGULATOR
V
CONTROL
CONTROL
BOOST
BOOST
BUCK
BUCK
POE1
VCC1
VCC2
GNDA
V1OK
V2OK
GNDA
POE2
iC-DC
iC-DC
VH1
VH2
22μH
22μH
VH
22μH
22μH
LVBH
LVBH
LVBH
LVBH
VBL
VBL
GND
GND
VHL
VHL
CVH
CVH
3.3μF
3.3μF
CVH1
CVH1
3.3μF
3.3μF
CVCC1
CVCC1
1μF
1μF
CVH2
CVH2
3.3μF
3.3μF
CVCC2
CVCC2
1μF
1μF
(3)
1.5...5.5V
1.5...5.5V
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2
1
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TES
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