PC87373 datasheet(28/174 Pages) NSC

28 / 174 page

2.0 Power, Reset and Clocks (Continued)

www.national.com

Revision 1.1

Figure 1 shows the power state transitions:

2.1.3

Power Connection and Layout Guidelines

The PC87373 requires a power supply voltage of 3.3V

± 10% for both the V

DD3 and VSB3 supplies. The on-chip Core power

converter generates a voltage below 3V for the internal logic. The device is designed to operate with a Lithium backup bat-

tery supplying up to 3.6V. Therefore, it includes an internal current-limiting resistor on the VBAT input to prevent the battery

from shorting, as required by the UL regulations. If the system implementation does not require backup power for the

PC87373 device, the VBAT pin must be connected to VSS through an external pull-down resistor.

VDD3, VSB3, VCORF and VBAT use a common ground return marked VSS.

To obtain the best performance, bear in mind the following recommendations.

Ground Connection. The following items must be connected to the ground layer (VSS) as close to the device as possible:

• The ground return (V

SS) pins

• The decoupling capacitors of the Main power supply (V

DD3) pins

• The decoupling capacitors of the Standby power supply (V

SB3) pins

Table 5. Power States and Related Power Planes

Power State

Main (VDD3)

Standby (VSB3)

Core (VCORF)

1. VCORF is generated from VSB3; therefore, both voltages are on or off at approximately the same time.

VBAT

Battery Fail2

2. This power state applies only to the SWC functions powered by VBAT.

On or Off

Off

Power Fail

Off

On or Off

Power Off

Off

On or Off

PowerOn

OnorOff

Illegal3

3. Operation is not guaranteed and register data may be corrupted. However, at power-on/off, the

device may temporarily enter this power state due to the different rise/fall times of the VDD3 and

VSB3 power supplies.

Off

On or Off

VDD3, VSB3, VCORF On or Off

Battery Fail

VDD3, VSB3 and VCORF Off,

Power Fail

VDD3 Off,

Power Off

VDD3, VSB3, VCORF and VBAT On

Power On

VBAT On

VBAT Power-Up Reset

VSB3 On,

VDD3 On,

VBAT Off

VSB3 Off

VDD3 Off

VSB3 On

VBAT Off

VBAT On generates

VDD3 On

VBAT Off

VSB Power-Up Reset

VDD Power-Up Reset

and VBAT Off

VBAT On

VSB3, VCORF and VBAT On

VSB3 Off

VBAT On

VBAT Off

Figure 1. Power State Transitions

PC87373 데이터시트(PDF) 28 Page - National Semiconductor (TI)

PC87373 데이터시트(HTML) 28 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

데이터시트 다운로드

링크 URL