PC87591L datasheet(361/437 Pages) NSC

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Host-Controlled Modules and Host Interface (Continued)

Revision 1.07

361

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Figure 119 shows typical battery current consumption during battery-backed operation; Figure 120 shows typical battery

current consumption during normal operation.

Figure 119. Typical Battery Current During Battery-Backed Power Mode

Figure 120. Typical Battery Current During Normal Operation Mode

6.2.10 System Bus Lockout

During power on or power off, spurious bus transactions from the host may occur. To protect the RTC internal registers from

corruption, all inputs are automatically locked out. The lockout condition is asserted when VCC is lower than VCCON.

6.2.11 Power-Up Detection

When system power is restored after a power failure or power off state (VCC=0), the lockout condition continues for a delay

of 62 ms (minimum) to 125 ms (maximum) after the RTC switches from battery to system power.

The lockout condition is switched off immediately in the following situations:

●

If the Divider Chain Control bits, DV0-2, (bits 6-4 in CRA register) specify a normal operation mode (0102), all input

signals are enabled immediately on detection of system voltage above VCCON.

●

When battery voltage is below VBATDCT and host domain hardware reset is active, all input signals are enabled im-

mediately on detection of system voltage above VCCON. This also initializes registers at offsets 0016 through 0D16.

●

If bit 7 (VRT) of CRD register is 0, all input signals are enabled immediately on detection of system voltage above VCCON.

time

VCC

VPP

VBAT

3.3V - 3.6V

VCC2PP

VPP2CC

VPP uses VCC

VPP uses VBAT

Figure 118. VPP Generation Using VCC or VBAT

VPP

VBAT

VCC

VPP uses VBAT

IBAT (µA)

1.0

0.9

0.8

0.7

2.4 3.0 3.6

VBAT (V)

IBAT (µA)

0.20

0.15

0.10

0.05

3.0 3.3 3.6

VCC

Note: Battery voltage in this test is 3.0V.

(V)

PC87591L Datasheet(PDF) 361 Page - National Semiconductor (TI)

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