DS8007 Maxim, DS8007 Datasheet - Page 26

• Manufacturer Part Number: DS8007
• Description: The DS8007 multiprotocol dual smart card interface is a low-cost, dual smart card reader interface supporting all ISO 7816, EMV®, and GSM11-11 requirements
• Manufacturer: Maxim

Card Interface Voltage Regulation
The V
Voltage supervisor circuitry detects the input voltage
levels and automatically engages a step-up converter if
necessary to generate the appropriate voltages to the
card interfaces according to the control register set-
tings. The conversion process is transparent to the user
and is usually only noticed by changes in the V
voltage, which reflects the operation of the internal
charge pump. Table 2 elaborates on the V
The V
but extra care must be taken to decouple large current
spikes that can occur on the V
noise generated by the cards and internal voltage step-
up circuitry.
The voltage supervisor circuitry monitors V
holds the device in reset until V
level. The DELAY pin is an external indicator of the
state of internal power and can also be driven external-
ly to hold the device in a reset state. An external capac-
itor is usually attached to this pin, defining the time
constant of a power-on delay for the DS8007. When
V
path that exists between V
nected and a strong pulldown is enabled on the DELAY
pin. Once V
the DELAY pin is released and the pullup to V
enabled, allowing the external DELAY capacitor to be
charged.
The RSTOUT alarm pin is released (allowing it to be
pulled up externally) whenever the DELAY pin voltage
is less than V
as a result of external hardware pulling the DELAY pin
Multiprotocol Dual Smart Card Interface
26
DD
and Step-Up Converter Operation
______________________________________________________________________________________
is below the voltage threshold V
DD
DD
and V
and V
Voltage Supply Supervision
DD
DRST
DDA
DDA
exceeds V
, whether caused by V
pins must be decoupled externally,
pins supply power to the DS8007.
RST
DD
, the strong pulldown on
and DELAY is discon-
DD
DDA
is at a satisfactory
RST
pins because of
, the charging
DD
UP
pin.
< V
DD
UP
RST
DD
and
pin
or
is
low. The minimum duration of the RSTOUT pulse (t
specification) is defined by the capacitor connected to
the DELAY pin and is typically 1ms per 2nF. The
RSTOUT pin is driven strongly low once the DELAY pin
exceeds the V
The SUPL bit is set on initial power-up and is reset
again when the RSTOUT alarm pulse occurs. The SUPL
bit may only be cleared by a read of the HSR register.
Figure 8 illustrates the sequencing of the various sig-
nals involved.
Short-circuit and thermal-protection circuitry prevent
damages done by accidentally shorting the V
or when the ambient temperature is exceeding the
maximum operating temperature. When the internal
temperature is approximately +150°C, the voltage V
and the drivers to the CLKx, RSTx, I/Ox, C4x, and C8x
signals to both card interfaces are turned off. The PTL
bit in the HSR is set and an interrupt is generated.
When a short is detected on the RSTx pin, the device
initiates a normal deactivation sequence. A short on
I/Ox, C4x, and C8x does not cause deactivation.
Table 2. Step-Up Converter Operation
2.4–3.5
3.5–5.5
5.5–6.0
2.4–3.5
2.4–6.0
V
< 2.4
> 3.5
DDA
DRST
voltage threshold.
VOLTAGE (V)
SMART CARD
3.0
3.0
1.8
X
5
5
5
V
V
V
V
V
5.7
5.7
4.1
UP
DDA
DDA
DDA
DDA
CCx
pins
CCx
W