MCIMX257CJM4A Freescale, MCIMX257CJM4A Datasheet - Page 10

• Manufacturer Part Number: MCIMX257CJM4A
• Manufacturer: Freescale

Specifications of MCIMX257CJM4A

• Lead Free Status / RoHS Status: Compliant

10
USBPHY1_RREF
OSC32K_EXTAL
NVCC_DRYICE
UPLL_BYPCLK
OSC32K_XTAL
USBPHY2_DM
USBPHY2_DP
POWER_FAIL
TEST_MODE
TAMPER_A,
TAMPER _B
SJC_MOD
OSC_BYP
Signal
REF
DryIce power supply output. The supply source is QVDD, when the i.MX25 is in run mode and the backup
supply is BATT_VDD when it is in reduced power mode. This pin can be used to power external
components (external tamper detect, wire-mesh tamper detect).
The 32 kHz oscillator bypass-control pin. If this signal is pulled down, then OSC32K_EXTAL and
OSC32K_XTAL analog pins should be tied to the external 32.768 kHz crystal circuit. If on the other hand
the signal is pulled up, then the external 32 kHz oscillator output clock must be connected to
OSC32K_EXTAL analog pin, and OSC32K_XTAL can be no connect (NC).
These analog pins are connected to an external 32 kHz CLK circuit depending on the state of OSC_BYP
pin (see the description of OSC_BYP under the preceding bullet). The 32 kHz reference CLK is required
for normal operation.
An interrupt from PMIC, which should be connected to a low-battery detection circuit. This signal is
internally connected to an on-chip 100 k pull-down device. If there is no low-battery detection, then users
can tie this pin to GND through a pull-down resistor, or leave the signal as NC. This pin can also be
configured to work as a normal GPIO.
External ADC reference voltage. REF may be tied to GND if the user plans to only use the internally
generated 2.5 V reference supply.
Must be externally connected to GND for normal operation. Termination to GND through an external
pull-down resistor (such as 1 k ) is allowed, but the value should be much smaller than the on-chip
100-k
DryIce external tamper detect pins, active high. If TAMPER_A or TAMPER_B is connected to
NVCC_DRYICE, then external tampering is detected. These pins can be left unconnected if the DryIce
security features are not being used.
For Freescale factory use only. This signal is internally connected to an on-chip pull-down device. Users
must either float this signal or tie it to GND.
Primarily for Freescale factory use. There is no internal on-chip pull-up/down on this pin, so it must be
externally connected to GND or VDD. Aside from factory use, this pin can also be configured (through
muxing) to work as a normal GPIO.
Determines the reference current for the USB PHY1 bandgap reference. An external 10 k 1% resistor to
GND is required.
The output impedance of these signals is expected at 10 . It is recommended to also have on-board 33
series resistors (close to the pins).
i.MX25 Applications Processor for Consumer and Industrial Products, Rev. 6
pull-up.
Table 4. Signal Considerations (continued)
Description
Freescale Semiconductor