73S8009C Maxim, 73S8009C Datasheet - Page 18
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73S8009C
Manufacturer Part Number
73S8009C
Description
The 73S8009C is a versatile power management and single smart card interface circuit that is ideally suited for smart card reader products that are battery- and/or USB bus-powered
Manufacturer
Maxim
Datasheet
1.73S8009C.pdf
(32 pages)
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73S8009C Data Sheet
3.2
The power supply and converter circuit takes power from any one of three sources; V
V
a voltage range of 2.7 to approximately 3.1 volts. V
volts. V
(6.5 V maximum). V
voltage value of 4.0 V to 6.5 V. V
an SPDT switch (break-before-make). They are not enabled at the same time. V
selected in lieu of V
source of V
V
The power supplied to the V
A series power inductor (nominal value = 10 µH) is connected from V
plus a 0.1 µF capacitor must be connected to V
nominal value of 5.5 V during normal operation. V
IO, AUX1, and AUX2) and is the source of the regulated smart card supply V
for values of 5 V, 3 V, and 1.8 V. V
logic, input/output buffering, and analog functions as well as being capable of supplying up to 40 mA of
current to external devices. Figure 4 shows the block diagram of the 73S8009C.
3.3
When no power is applied to the V
be inoperative during the “OFF” state, consuming minimum current from V
supplied, the functions of the ON/OFF switch and circuitry are overridden and the 73S8009C is in the
“ON” state with V
only to the ON_OFF pin. The ON_OFF pin shall be connected to a SPST switch to ground. If the circuit
is OFF and the switch is closed for a de-bounce period of 50-100ms, the circuit shall go into the “ON”
state wherein all functions are operating in normal fashion. If the circuit is in the “ON” state and the
ON_OFF pin is connected to ground for a period greater than the de-bounce period, OFF_REQ will be
asserted high and held. Typically, the OFF_REQ signal is presented to a host controller that will assert
OFF_ACK high when it has completed all shutdown activities. When OFF_ACK is set high, the circuit will
de-activate the smart card interface if required and turn off all analog functions and the V
logic and companion circuits. The OFF_ACK pin is connected internally to OFF_REQ with a resistor such
that if OFF_ACK is unconnected, the action of OFF_REQ will assert OFF_ACK high. In this
configuration, the circuit shall go into the “OFF” state immediately upon OFF_REQ = 1. The default state
upon application of power is the “OFF” state unless power is supplied to the V
time, the controller may assert OFF_ACK and the 73S8009C will go into the “OFF” state (when V
not present.)
If power is applied to both V
source. The circuit will be unconditionally “ON” when V
circuit will switchover to the VBAT input supply and remain in the “ON” state. The controller circuit
firmware is required to assert OFF_ACK based on no activity or V
consumption. When operating from V
switch connecting V
“SUSPEND” state. The USB “SUSPEND” state requires the power supply current to be less than 500 µA.
In order to obtain and meet this low current limitation, the companion controller must be configured into a
power-down condition using less than 20 µA from V
Note: When using the VBUS input as the sole power source for an ‘always on’ configuration
(ON_OFF input not used), the OFF_ACK and ON_OFF inputs must be connected to ground.
18
PC
PC
is specified to range from 2.7 to 6.5 volts and would typically be supplied by a single cell battery with
source.
Power Supply and Converter
Power ON/OFF
BUS
PC
is typically supplied by a connected USB cable and ranges in value from 4.5 to 5.5 volts
must be diode isolated from the V
P
and V
BAT
BUS
BAT
when V
to V
is expected to be supplied from a battery of two series connected cells with a
DD
available. Without V
P
BAT
PC
in order to save power. This condition is appropriate for the USB
BUS
is up-converted to the voltage V
and V
BAT
is present. If V
BUS
DD
and V
BUS
pin, a power ON/OFF function is provided such that the circuit will
BUS
is also produced from V
, the circuit will automatically consume power from only the V
, and not calling for V
BUS
are connected to V
PC
PC
BUS
PC
. V
P
pin to prevent current flow from V
PC
DD
applied, and in the OFF state, the circuit responds
is used by the smartcard interface circuits (CLK, RST,
is provided and V
P
.
is also appropriate for system supplies of 3.3 or 5
requires a 4.7 µF filter capacitor and will have a
BUS
is applied. If the V
P
CC
P
. V
utilizing an inductive, step-up converter.
, the step-up converter becomes a simple
BUS
PC
DD
by two FET switches configured as
PC
is used by the 73S8009C circuit for
removal to reduce battery power
BAT
to LIN, and a 10 µF filter capacitor
or V
PC
CC
and V
BUS
BUS
BUS
. V
are also used, the
source is removed, the
BUS
supply. Note that at any
CC
BAT
BAT
can be programmed
is automatically
PC
. If V
, V
or V
DD
DS_8009C_025
BUS
BUS
supply for the
BUS
, and V
power is
into the
BUS
Rev. 1.5
BAT
is
BUS
.