Charging

At the phone end there is no difference between a plug-in charger or a desktop charger. The DC-jack pins and bottom connector charging pads are connected together inside the phone.

Nokia 3210 Charger Specification
Figure 13. Charging Block Diagram

The PSCC is the charging control ASIC, basically a CHAPS known from DCT3 but modified for operation on lower supply level and reduced for 2 cell NiMH battery only. The ASIC has the following main functions:

- controlled low drop power switch

- input transient voltage protection

- thermal self protection

- output over voltage protection (voltage limit for phone hardware)

- start-up regulator with limited charge current, Istart

- provision for soft switching (external capacitor needed), C126

- control of different charger types (different PWM frequencies 1Hz and 32Hz)

The power switch is controlled according to PWM input via V114a. PSCC_PWM is supplied from the MAD and is different from the external charge control PWM signal, which is supplied by the CCONT. When PSCC_PWM is low, the switch is turned On and the output current, lout, equals the charger current , except for the internal PSCC supply consumption.

When PSCC_PWM is high, the switch is OFF and the output current is zero or Istart , depending upon Vb. In MAD2PR1 power on / reset mode PSCC_PWM is default high.

When Vb is below Vstart limit and it is needed to stop any charging current (even Istart), e.g. when detecting external audio accessory, the MAD can disable any charge current by commanding CTIM pin low via V114b by setting CHARG_OFF signal high. The MAD pin controlling V114b is low during power on / reset. The CHARGE_OFF signal always takes precedence over PSCC_PWM, i.e. Istart is zero.

Table 22. PSCC characteristics

Parameter

Symbol

Min

Typ

Max

Unit

Vb limit @ IStart cutoff

Vstart

2.33

2.43

2.52

V

Start-up regulator output current @Vb = 0 V ... Vstart

Istart

150

180

210

mA

Charging current limitation

Icharge

1.5

1.8

2.1

A

Vb Output voltage cutoff limit

Vlim

3.32

3.46

3.6

V

Charger input voltage protection limit

Vch

18

V

Vb threshold voltage to enter PWM mode

Vpwm

1.9

2.0

2.1

V

PWM input logic control levels

Vil

0

0.7

V

Vih

1.8

2.85

When a charger is connected, the PSCC is supplying a startup current, Istart to the battery.

Istart provides initial charging to the phone with an empty battery. The PSCC charges the battery until Vb reaches the switcher start up voltage, where the DC/DC converter powers up at it's lowest output voltage level. When Vdc_out reaches 3.0 V the CCONT powers up, recognizes charger input, releases PURX reset signal and program execution starts. If the current consumption is too high, Vb will drop below the switcher shutdown limit, and it shuts down. The PSCC will continue charging with Istart. Vb increases again and the power on sequence will repeat as described until Vb and the energy content of the battery is sufficiently high to support a full Baseband / MCU power on by the phone. The MCU SW controls when the charging mode is changed from startup-charging to PWM-charging (fast charging).

System Module

Technical Documentation

If the battery voltage reaches Vstart limit, before the SW has taken control over the charging, the startup current is switched off by the PSCC.

Software controlled charging

PWM charging (fast charging) is controlled by the MCU software. The sw performs a charger detection and tries to recognize the charger by a mix of charger voltage, and charger current measurement ) via the ADC's in CCONT.

When the charger has been recognized as valid, the SW tries to force the PSCC into fast charging, by pulling PSCC_PWM low, no matter how low the battery voltage is. As soon as Vb reaches the threshold when the internal state of the PSCC is changed to PWM mode ( Vb>Vpwm) the PSCC responds to the PWM control and closes the internal power switch. In this state the charging current is determined by the actual charger.

When using a 3 wire charger (ACP-9 type) the external charge control signal, CHARG_CTRL, is supplied with a constant 32Hz with a duty cycle of 25% high, 75% low PWM signal originated from the PWM output in CCONT. The three wire charger is thus supplying a voltage of about 7 V. The PSCC_PWM is controlled as for the other chargers. Two wire chargers supplies maximum voltage according to their current capability.

The SW is capable of controlling the charge current by PSCC_PWM signal from MAD. When PSCC_PWM is low the PSCC power switch is closed thus max current is flowing. When PSCC_PWM is high the switch is open, thus no current is flowing (except Istart, if Vb is below the threshold, and the state of the CHARGE_OFF signal).

Battery over voltage protection

Vb over voltage protection is used to protect the phone against damage. This function is also used to define the charging cutoff voltage for the battery.

Output over voltage protection is needed also in the case if the battery is removed when a charger is connected (or a charger is connected to the phone before the battery ).

The power switch is immediately opened if Vb rises above the threshold voltage VLIM. When the switch in output over voltage state has once turned OFF, it stays OFF until the charger has been disconnected and re-inserted.

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