PCA5010 datasheet(67/112 Pages) PHILIPS

67 / 112 page

1998 Nov 02

Philips Semiconductors

Product speciﬁcation

Pager baseband controller

PCA5010

6.22.4

DESCRIPTION OF OPERATING MODES

6.22.4.1

Normal operating mode

Once the system is powered-up successfully (STB = 1),

the DC/DC converter is in normal operating mode. This

mode has two sub modes:

• Normal mode

• Standby mode.

By setting/resetting the standby bit in DCCON0 (D1H), the

DC/DC converter switches between normal mode and

standby mode. Switching between these two modes is

possible at any time by software if the controller is in

normal operating mode. Normal operating mode can be

exited by any of the following events:

• HIGH level at the RESETIN pin

• A watchdog reset, which will force the same sequence

as an off command

• Writing the off bit in DCCON0.

Setting the off bit in DCCON0 forces the converter into

DC/DC converter off mode.

6.22.4.2

Normal mode

Normal mode is the high efficiency mode of the DC/DC

converter. In this mode the controller can keep VDD stable

at 2.2 V up to the maximum available current (see Fig.37).

The output voltage is regulated in a small window and the

current peaks in the coil are kept as small as possible (see

Fig.45). After a reset and the following start-up sequence,

the controller is in normal mode.

To shorten the settling time when the receiver is switched

on or off, the DC/DC converter uses 2 sets of coefficients.

One for low output current and one for high output current.

When the RXE bit in DCCON0 is set, the DC/DC converter

stores the actual coefficients for low output current and

switches to the coefficients for high load current. At the

same time the receiver should be enabled. When the

battery voltage did not change very much since the last

time the receiver was on, the settling time is only a few

microseconds instead of a few hundreds of microseconds

when not using the RXE bit. When switching off the

receiver, the RXE bit in DCCON0 should be reset. In this

case, the DC/DC converter stores the new values for high

output current and restores the values for low output

current. It should be noted that the RXE bit does not

change the algorithm of the DC/DC converter but shortens

the settling time dramatically.

When the load is so high that the required output current

cannot be delivered, the DC/DC converter resets the

signal STB and a DC/DC interrupt is issued to the

processor via IRQ SFR IRQ1.5. STB = 0 flags the inability

to deliver enough current in normal mode or in standby

mode. When the STB flag is set to logic 0, VDD can drop

very quickly, depending on the battery voltage and the

load.

6.22.4.3

Standby mode

Standby mode is a low current mode which can be used

when only the microcontroller is running and the quality of

VDD is not important. In standby mode the DC/DC

converter uses the 76.8 kHz clock instead of the 6 MHz

clock. This reduces the current consumption of the DC/DC

converter. The maximum output current in this mode is

limited to a few milliamps (see Fig.38). In standby mode

VDD can be set to 1.9, 2.0, 2.1 or 2.2 V by setting the

VLO1 and VLO0 bits in DCCON1 to the corresponding

values. When the load is so high that the required output

current cannot be delivered, the DC/DC converter resets

the signal STB and a DC/DC interrupt is issued to the

processor via IRQ SFR IRQ1.5. In this case, the

microcontroller should switch off the different loads and

switch to normal mode.

6.22.4.4

Off mode

Off mode can only be entered by setting the off bit in

DCCON0 by software. The DC/DC converter waits for

15 periods of the 76.8 kHz clock before it sets VDD to VBAT

and switches off completely (see Fig.41). In the off mode

the PMOS is conducting and therefore it is guaranteed that

VDD never drops below VBAT − 100 mV. When the DC/DC

converter is in off mode, one of the following events can

restart the converter:

• P1X (independent from interrupt enabling or polarity)

• Minute

• Wake-up

• RESETIN pulse.

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