ncn6000 ON Semiconductor, ncn6000 Datasheet - Page 22

• Manufacturer Part Number: ncn6000
• Description: Compact Smart Card Interface Ic
• Manufacturer: ON Semiconductor

Vbat Supply Voltage Monitoring
reference, continuously monitors the +Vbat input. During
the start up, all the NCN6000 functions are deactivated and
no data transfer can take place. When the +Vbat voltage rises
above 2.35 V (typical), the chip is activated and all the
functions becomes available. The typical behavior is
provided here after Figure 16. At this point, the internal
Power On Reset signal is activated (not accessible
externally) and all the logic signals are forced into the states
as defined by Table 3.
the operation, the NCN6000 generate a Power Down
sequence and is forced in a no operation mode. The built−in
100 mV (typical) hysteresis avoids unstable operation when
the battery voltage slowly varies around the 2.30 V.
STATUS signal, pin 5, to control the state of the battery prior
to launch either a NCN6000 programming or an ATR
sequence (Table 4).
The built−in comparator, associated with the band gap
If the +Vbat voltage drops below 2.25 V (typical) during
On the other hand, the microcontroller can read the
PWR_ON
3 V/ 5 V
Overload
VCC_OK
V
ref
Active Pull Down
V
out
_3_5
V
ref
_3/5 V
V
bat
PMOS Gate Drive
NMOS Gate Drive
Voltage Regulation
Substrat Bias
MOS Drive
U3
GND
−
+
Figure 17. Basic DC−DC Structure
V
bat
Current Sense
/V
CC
http://onsemi.com
Comparator
NCN6000
GND
V
U2
bat
−
+
22
Q1
GND
Vbat STATUS
DC−DC Converter Operation
boost structure to cover the full battery and card operating
voltage range. The built−in battery voltage monitor provides
an automatic system to accommodate the mode of operation
whatever be the Vbat and CRD_VCC voltages. Comparator
U3/Figure 17 tracks the two voltages and set up the
operating mode accordingly.
GND
U1
The built−in DC−DC converter is based on a modified
Vbat_OK
+
−
Note: Drawing is not to scale and voltages are typical.
3.30 V
2.80 V
2.35 V
2.25 V
Q2
Vbat
Figure 16. Typical Vbat Monitoring
Q3
R1
See specifications data for details.
GND
R2
R3
R4
1R
GND
Q4
GND
20
19
18
15
17
CRD_VCC
L
L
PWR_GND
V
out_H
out_L
bat
V
bat
C1
GND
L2
22 mH
+