MAX1840/MAX1841
Low-Voltage SIM/Smart Card
Level Translators in µMAX
6 _______________________________________________________________________________________
Detailed Description
The MAX1840/MAX1841 provide the necessary level
translation for interfacing with SIMs and smart cards in
multivoltage systems. These devices operate with logic
supply voltages between +1.4V and +5.5V on the con-
troller side (DV
CC
) and between +1.7V and +5.5V on the
card side (V
CC
). The total supply current (I
DV
CC
+ I
V
CC
)
is 1µA while operating in an idle state (see Electrical
Characteristics). Figure 1 shows the MAX1840/MAX1841
test circuit. The Typical Application Circuit appears at the
end of this data sheet.
Level Translation
The MAX1840/MAX1841 provide level translators for a
clock input, a reset input, and a bidirectional data IO.
The clock and reset inputs (CIN and RIN) are level shift-
ed from the controller-side supply rails (DV
CC
to GND)
to the card-side supply rails (V
CC
to GND). When con-
nected to an open-drain controller output, DATA and IO
provide bidirectional level translation. All level transla-
tion is valid for DV
CC
≥ V
CC
or DV
CC
≤ V
CC
. The
MAX1840/MAX1841 contain internal pull up resistors
from DATA to the controller-side supply (DV
CC
) and
from IO to the card-side supply (V
CC
). For push-pull
controller outputs, see the Data Driver section for bidi-
rectional data translation.
Data Driver (MAX1841 Only)
When using a microcontroller (µC) without an open-drain
output, use the data driver (DDRV) input to send data to
the SIM/smart card, while DATA provides the controller-
side output for bidirectional data transfer. When not
used, connect DDRV to DV
CC
to reduce total supply cur-
rent.
Shutdown Mode
For the MAX1840, drive SHDN low to activate shut-
down. Connect SHDN to DV
CC
or drive high for normal
operation. To allow for card insertion and removal, shut-
down mode actively pulls CLK, RST, and IO low; it also
disconnects the internal 10kΩ pull up resistor from V
CC
to prevent excessive current draw. Shutdown mode
reduces the total supply current (I
DVCC
+ I
VCC
) to
0.01µA.
SIM/Smart Card Insertion/Removal
The SIM/smart card specifications require that the card-
side pins (V
CC
, CLK, RST, IO) be at ground potential
prior to inserting the SIM/smart card. For applications
using the MAX1686H (Figure 3), the easiest way to
achieve this is by shutting down the MAX1686H or by
driving SHDN (MAX1840 only) low. If specific sequenc-
ing is desired, pull IO low by driving either DATA or
DDRV (MAX1841 only) low, and pull CLK and RST low
by driving CIN and RIN low, respectively.
ESD Protection
As with all Maxim devices, ESD-protection structures on
all pins protect against ESDs encountered during han-
dling and assembly. For further protection during card
insertion and removal, the pins that connect to the card
socket (CLK, RST, IO, V
CC
, and GND) provide protec-
tion against ±10kV of ESD. The ESD structures with-
stand high ESD in all states: normal operation,
shutdown, and power-down. After an ESD event, the
MAX1840/MAX1841 continue working without latchup.
A 1µF bypass capacitor from V
CC
to GND is required to
exceed ±10kV ESD specifications.
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report documenting test
setup, test methodology, and test results.
Applications Information
SIM/Smart Card Interface
To provide 5V when interfacing with a 5V SIM/smart card,
+3V systems require a DC-DC converter. The MAX1686H
+5V regulating charge pump for SIM cards provides
DDRV FOR MAX1841 ONLY.
TEST PROBES AND BOARD LAYOUT.
