AIC1568
BLOCK DIAGRAM
115%
110%
VSEN
+
=
-
POWER-ON
RESET
OVP
VCC
90%
50%
1µA
+
=
-
POWER GOOD
+
-
+
-
−
+
OVER
CURRENT
PGOOD
OCSET
SS
4V
I
OCSET
200µA
PHASE
SOFT
SATRT
REFERENCE
VID0
VID1
VID2
VID3
FB
COMP
OSCILLATOR
RT/OVP
VDAC
4BITS
DAC
+
-
ERROR
AMP
+
+
−
CONTROL
LOGIC
PWM
COMPARATOR
UGATE
BOOT
GND
PIN DESCRIPTIONS
PIN 1: OCSET - Current limit sense pin. Connect
a resistor R
OCSET
from this pin to
the drain of the external
MOSFET. R
OCSET
, an internal 200
µA
current source (I
OCSET
), and
the external MOSFET on-
resistance (R
DS(ON)
) jointly set the
over current trip point according
to the following equation:
An internal 10µA current source
provides soft start function for
the converter.
PIN 3:
PIN 4:
PIN 5:
PIN 6:
VID0
VID1
VID2
VID3
-
-
-
- 4-bit DAC voltage select pin. TTL
inputs used to set the internal
voltage reference VDAC. When
left open, these pins are
internally pulled up to 5V and
provide logic ones. The level of
VDAC sets the converter output
voltage as well as the PGOOD
and OVP thresholds.
Table 1 specifies the VDAC
voltage for the 16 combinations
of DAC inputs.
I
PEAK
=
I
OCSET
×
R
OCSET
R
DS(ON)
If FB pin voltage is sensed to be
below 50% of the internal
voltage reference VDAC, the
over current comparator cycles
the soft-start function.
PIN 2: SS
- Soft start pin. Connect a
capacitor from this pin to ground.
5
AIC [ ANALOG INTERGRATIONS CORPORATION ]
