MC33348 데이터 시트보기 (PDF) - Motorola => Freescale

부품명

상세내역

제조사

MC33348

Lithium Battery Protection Circuit for One Cell Battery Packs

Motorola => Freescale 

MC33348

As previously stated in the voltage sensing operating

low threshold MOSFETs, it may be desirable to disable the

description, charge MOSFET Q1 is held off during an

Charge Pump so that the maximum gate to source voltage is

overvoltage fault condition. When this condition is present,

not exceeded. This can be accomplished by connecting Pin 6

the discharge current limit protection function is internally

to Pin 5, and will result in an additional cell drain current of

disabled. This is required, since the voltage across Q1, in the

approximately 8.0 µA.

off state, would exceed the current sense threshold. This

would cause Q2 to turn off as well, preventing both charging

and discharging of the cell. Discharge current limit protection

is enabled whenever an overvoltage fault is not present.

The discharge current protection circuit contains a built in

response delay of 3.0 ms. This helps to prevent fault

activation when the battery pack is subjected to pulsed

Testing

A test pin is provided in order to speed up device and

battery pack testing. By grounding Pin 2, the internal logic is

held in a reset state and both MOSFET switches are turned

on. Upon release, the logic becomes active and the cell

voltage is polled within 1.0 ms.

currents during discharging. An additional current sense

delay can be added as shown in Figure 12. If the battery pack

is subjected to extremely high discharge current pulses or is

shorted, the VCC pin must be decoupled from the cell. This is

required so that the protection circuit will have sufficient

operating voltage during the load transient, to ensure turn off

of discharge MOSFET Q2. Figure 13 shows the placement of

decoupling components.

Battery Pack Application

The one cell smart battery pack application shown in

Figure 7 contains a capacitor labeled CI that connects

directly across the battery pack terminals. This component

prevents excessive currents from flowing into the MC33348

when the battery pack terminals are shorted or arced, and is

mandatory. Capacitor CI is a 100 nF ±20% ceramic leaded

or surface mount type. It must be placed directly across the

Charge Pump and MOSFET Switches

The MC33348 contains an on chip Charge Pump to

ensure that the MOSFET switches are fully enhanced for

reduced power losses. An external reservoir capacitor

normally connects from the Charge Pump output to ground,

Pins 8 and 3. The capacitor value is not critical and is usually

within the range of 10 nF to 100 nF. The Charge Pump output

is regulated at 10.2 V allowing the use of the more

economical logic level MOSFETs. The main requirement in

selecting a particular type of MOSFET switch is to consider

the desired on–resistance at the lowest anticipated operating

voltage of the battery pack. A table of small outline surface

battery pack plus and minus terminals with extremely short

lead lengths (≤1/16″).

In applications where inordinately low leakage MOSFETs

are used, the protection circuit may take a considerable

amount of time to reset from an overcurrent fault after the

load is removed. This situation can be remedied by providing

a small leakage path for charging CI, thus allowing Pin 5 to

rapidly fall below the discharge current limit threshold. A

1.0 megohm resistor placed across the MOSFET switches

accomplishes this task with a minimum increase in cell

discharge current when the battery pack is connected to a

load.

mount devices is given in Figure 14. When using extremely

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Device

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Type

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MMFT3055VL

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MMDF3N03HD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MMDF4N01HD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MMSF5N02HD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ MMDF6N02HD

Figure 14. Small Outline Surface Mount MOSFET Switches

On–Resistance (Ω) versus Gate to Source Voltage (V)

2.5 V

3.0 V

4.0 V

5.0 V

6.0 V

7.5 V

–

–

–

0.120 Ω

0.115 Ω

0.108 Ω

–

0.525 Ω

0.080 Ω

0.065 Ω

0.063 Ω

0.062 Ω

0.047 Ω

0.042 Ω

0.037 Ω

0.035 Ω

0.034 Ω

0.033 Ω

–

0.065 Ω

0.023 Ω

0.021 Ω

0.020 Ω

0.018 Ω

0.043 Ω

0.035 Ω

0.029 Ω

0.028 Ω

0.026 Ω

0.025 Ω

9.0 V

0.100 Ω

0.060 Ω

0.033 Ω

0.018 Ω

0.023 Ω

MOTOROLA ANALOG IC DEVICE DATA

9

Share Link: