RM48L540 datasheet(49/152 Pages) TI1

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RM48L940

RM48L740

RM48L540

www.ti.com

SPNS175

– SEPTEMBER 2011

4.2

Voltage Monitor Characteristics

A voltage monitor is implemented on this device. The purpose of this voltage monitor is to eliminate the

requirement for a specific sequence when powering up the core and I/O voltage supplies.

4.2.1

Important Considerations

•

The voltage monitor does not eliminate the need of a voltage supervisor circuit to guarantee that the

device is held in reset when the voltage supplies are out of range.

•

The voltage monitor only monitors the core supply (VCC) and the I/O supply (VCCIO). The other

supplies are not monitored by the VMON. For example, if the VCCAD or VCCP are supplied from a

source different from that for VCCIO, then there is no internal voltage monitor for the VCCAD and

VCCP supplies.

4.2.2

Voltage Monitor Operation

The voltage monitor generates the Power Good MCU signal (PGMCU) as well as the I/Os Power Good IO

signal (PGIO) on the device. During power-up or power-down, the PGMCU and PGIO are driven low when

the core or I/O supplies are lower than the specified minimum monitoring thresholds. The PGIO and

PGMCU being low isolates the core logic as well as the I/O controls during the power-up or power-down

of the supplies. This allows the core and I/O supplies to be powered up or down in any order.

When the voltage monitor detects a low voltage on the I/O supply, it will assert a power-on reset. When

the voltage monitor detects an out-of-range voltage on the core supply, it asynchronously makes all output

pins high impedance, and asserts a power-on reset. The voltage monitor is disabled when the device

enters a low power mode.

The VMON also incorporates a glitch filter for the nPORRST input. Refer to Section 4.3.3.1 for the timing

information on this glitch filter.

Table 4-1. Voltage Monitoring Specifications

PARAMETER

MIN

TYP

MAX

UNIT

VCC low - VCC level below this

0.8

0.9

1.0

threshold is detected as too low.

Voltage monitoring

VCC high - VCC level above this

1.40

1.7

2.1

VMON

thresholds

threshold is detected as too high.

VCCIO low - VCCIO level below this

1.9

2.4

2.9

threshold is detected as too low.

4.2.3

Supply Filtering

The VMON has the capability to filter glitches on the VCC and VCCIO supplies.

The following table shows the characteristics of the supply filtering. Glitches in the supply larger than the

maximum specification cannot be filtered.

Table 4-2. VMON Supply Glitch Filtering Capability

Parameter

MIN

MAX

Width of glitch on VCC that can be filtered

250ns

1us

Width of glitch on VCCIO that can be filtered

250ns

1us

System Information and Electrical Specifications

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