Datasheet SM6780AS Datasheet (NPC)

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Page 1

−∆

SM6780AS

NIPPON PRECISION CIRCUITS INC.

Ni-Cd/Ni-MH Battery Charger IC

OVERVIEW

The SM6780AS is a quick charge control IC for Nickel-Cadmium (Ni-Cd) and Nickel Metal Hydride (Ni-MH) rechargeable batteries. It supports quick charge, supplemental and pulse trickle charging modes. The charging mode is selected automatically in response to the battery voltage, temperature and charging time.

The quick charge uses either negative delta voltage detection ( −∆ V), temperature detection ( ∆ T/ ∆ t), or charging time cutoff to control the charging process. In addition, the quick charge mode can be placed on hold, if the battery voltage or battery temperature are abnormal, until normal conditions are restored.

The SM6780AS requires few external components to realize a high-stability quick charge battery charger.

FEATURES

■

Ni-Cd/Ni-MH battery quick charge control

■

V, ∆ T/ ∆ t, and maximum charge time cutoffs

■

3 charge modes (quick charge, supplemental, pulse trickle charge)

■

3 selectable charge times (80, 120, and 240 minutes)

■

Charge condition LED indicator output (on, pulsed, off)

■

Low power dissipation mode

■

4.0 to 5.5V operating supply voltage

■

300sec (typ) −∆ V detection invalid time

■

8mV (typ) −∆ V detection accuracy

■

25mV/min (typ) ∆ T/ ∆ t detection accuracy

■

8-pin SOP package

PINOUT

(Top view)

TIME CHGN

LEDN

BATT

VSS

6780AS

INH VDD TEMP

ORDERING INFORMATION

Device Package

SM6780AS 8-pin SOP

PACKAGE DIMENSIONS

(Unit: mm)

4.4 0.2

6.2 0.3

0.695typ

1.5 0.1

1.27

5.2 0.3

0.05 0.05

0.10

0.4 0.1

0.12

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0.15

− 0.05

0.4 0.2

0.1

0 to 10

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BLOCK DIAGRAM

Input

SM6780AS

VDD

TIMEVDD

Current

Source

Battery

Pack

NTC

BATT

TEMP

Reference

Regulators

Maximum

Cell-voltage Check

Input Select

Temp Check

A/D

OSC

−∆V

Function

Block

∆V/∆t

Function

Block

VSS

PIN DESCRIPTION

Number Name Description

1 TIME

2 LEDN

3BATT

4 VSS Ground 5 TEMP Battery temperature thermistor sensor voltage input 6 VDD Supply

7 INH

8 CHGN

Charge time select 3-level input. HIGH: 240 minutes, MID (V

/2): 120 minutes, LOW: 80 minutes

Charge indicator LED driver output. Open-drain output. LOW-level output in quick charge mode. 1Hz pulse output when abnormal battery voltage or temperature is detected during quick charge mode. High impedance output in supplemental and trickle charge modes.

Battery voltage detector input. Connect a high-impedance resistor voltage divider between the poles of the battery for v oltage detection.

Charge inhibit input. Charging is stopped when HIGH. Charging resumes with the same charge parameters in force prior to the stop when INH goes LOW again.

Charger control output. Open-drain output. Battery charging current ﬂows when CHGN is high impedance. Charge current stops when LOW. High-impedance output in quick charge mode, and pulse output in supplemental and trickle charge modes.

Timer Mode

Selector

Timing Control

Logic

Charge Control

Logic

CHGN

CHG Driver

VDD

LEDN

LED Driver

VDD

INH

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≤

−

SPECIFICATIONS

Absolute Maximum Ratings

= 0V

Parameter Symbol Condition Rating Unit

Supply voltage range V Input voltage range V Storage temperature range T Operating temperature range T Power dissipation P

DC Characteristics 1

stg

opr

−

SM6780AS

0.3 to 7.0 V

0.3 to 7.0 V 55 to 125

0 to 85

150 mW

° C ° C

= 4.0 to 5.5V, V

= 0V, Ta = 25 ° C

Parameter Symbol Condition Rating Variation Unit

Maximum temperature voltage V High-temperature sense

voltage Low-temperature sense voltage V

Maximum battery voltage V

MXT

HTS

LTS

MXV

DC Characteristics 2

= 4.0 to 5.5V, V

Parameter Symbol Condition

VDD supply voltage V BATT input voltage V TEMP input voltage V INH HIGH-level input voltage V INH LOW-level input voltage V TIME HIGH-level input voltage V TIME MID-level input voltage V TIME LOW-level input voltage V

V detection voltage range V

BATT −∆ LEDN output pulse frequency f BATT standby voltage V VDD current consumption I VDD standby current I LEDN, CHGN sink current I INH, TIME input leakage current I LEDN, CHGN output leakage

current

= 0V, Ta = 0 to 85 ° C unless otherwise noted

BATT

TEMP

IH1

IL1

IH2

IL2

DET

LED

STB

TEMP

HTS

> V

TEMP

> V

BATT

prohibition

charge cutoff 0.225V

MXT

TEMP

LTS

MXV

charge start 0.25V

LTS

charge prohibition 0.4V charge cutoff or

2.0 ±5% V

±5% V

Rating

min typ ma x

4.0 5.0 5.5 V 0–V

Disabled when V

< 0.5V 0.5 – V

TEMP

0.7 – – V – – 0.1 V

− 0.5 – – V

/2) − 0.5 – (V

– – 0.5 V 1–2V –1–Hz

1.5 – V

= 5V, no load – – 0.5 mA

V V V

INH

= 5V, V

= V

BATT

+ 0.8V 10 – – mA

TIME

, no load – – 1 µA

= V

to V

––±1µA

5– –µA

/2) + 0.5 V

0.5 V

Unit

V V

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FUNCTIONAL DESCRIPTION

Charger Operation

SM6780AS

The SM6780AS battery charger operation starts when the power is applied or when standby mode is released. The charging operation is determined by the BATT and TEMP pin states, and the timer mode selected.

After charging starts, the battery voltage and temperature are monitored to check that they are within quick charging rated ranges. If within rated range, quick charge mode is selected. If outside rated range, pulse trickle charge mode is selected.

Charging Rate

The charging rate is determined by the external charger current source. If the quick charge mode charging rate is considered as unity, then the supplemental charging rate is 1/16, and the pulse trickle charging rate is 1/256. The charging rate for supple-

286µs

Hi-Z

Low

4576µs

Quick charge uses either negative delta voltage detection ( −∆ V), temperature detection ( ∆ T/ ∆ t), or charging time cutoff to terminate the charging process. The charging mode changes to supplemental charge mode when quick charge mode is completed.

Supplemental mode terminates when the charging time ﬁnishes or battery is full, and the charging mode changes to pulse trickle mode.

mental and pulse trickle modes are shown in ﬁgure 1. The CHGN output is high impedance when the charging current is ﬂowing, and LOW when the current stops.

286µs

73.1ms

Quick charge

mode

Start (power ON or battery insertion)

Supplemental

charge mode Pulse trickle mode

Figure 1. CHGN output (external charger control)

Charging Status Indicator LED Control (LEDN)

The SM6780AS LEDN output can be used to drive a charging status indicator LED.

The LED timing when power is applied or standby mode is released is shown in ﬁgure 2.

Hi-Z

LED OFF

Low

Approximately

1.5 s

Power ON or Standby mode cancel

LED ON

Approximately

3.5 s

In quick charge mode, the LEDN output is LOW and the LED turns ON. If the battery temperature or battery voltage exceeds the charging rated ranges, the LEDN output pulses at a frequency of 1Hz to indicate battery out-of-range condition. In supplemental and pulse trickle modes, the LEDN output is high impedance and the LED turns OFF.

Depends on charge mode

Figure 2. LEDN output timing

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SM6780AS

Battery Voltage and Temperature Detection

The battery voltage detector input is BATT. The charger treats the input voltage as the equivalent voltage of a single cell. For multiple cells (connected in series), a high-resistance (> 100k Ω ) battery divider can be used to input the voltage equivalent of a single cell, as shown in ﬁgure 3.

BATT pin

The battery temperature detector input is TEMP. The input voltage is provided by a negative temperature coefﬁcient thermistor (NTC thermistor) located in close proximity to the battery, as shown in ﬁgure 4. The input voltage range is 0.5V to V

Battery

Figure 3. BATT connection example

Battery

NTC

Figure 4. TEMP connection example

= N − 1

N:Number of cells

TEMP pin

Note that the thermistor temperature characteristics are non-linear, so a correction resistance Rc should be used for linearity correction. The temperature rating of resistances Rc and Rd should be chosen to

match the battery temperature range rating. If the temperature detection function is not used, the TEMP input should be ﬁxed at a potential in the range 0.25V

to 0.4V

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Charging Modes

SM6780AS

The SM6780AS has 3 modes of operation: quick charge, supplemental charge, and pulse trickle mode.

The SM6780AS uses the various detection functions to monitor the state of the battery and select the charging mode automatically.

Hi-Z

CHGN output Cell voltage

Low

Quick charge mode

Start

In quick charge mode, charging occurs at a rate set by the external current source. In supplemental charge mode, the battery is charged by current pulses to the full stable capacity of the chemical substances within the battery. Pulse trickle mode maintains the level within the battery, compensating for internal losses.

Supplemental

charge mode

Quick charge

mode end

Charge

complete

Pulse trickle

mode

Figure 5. Charging mode, battery voltage and charging current

Quick (Supplemental) Charge Conditions — Battery Check

The SM6780AS monitors the battery voltage and battery temperature to conﬁrm the values are within the rated range of the battery during quick charge and supplemental charging modes to realize a highstability battery charger.

If the battery voltage or battery temperature charging rating is exceeded before quick charging mode terminates, the charging mode is placed on hold. The

Low temperature sense

Maximum cell

Voltage

2.0V

Charge

valid range

Voltage (0.4 × V

High temperature sense

Voltage (0.25 × V

Maximum temperature

Voltage (0.225 × V

DD)

Charge

valid range

DD)

internal timer continues to operate, and pulse trickle charging occurs. The LEDN output pulses at a rate of approximately 1Hz. If the charging rating is exceeded during supplemental charging mode, the mode terminates and charging switches to pulse trickle mode.

VTEMP VBATT

Pulse trickle

Power ON

Pulse trickle

mode

Quick charge

start

Quick charge

mode

Quick charge is suspended

High-temperature quick charge hold state: V High-temperature quick charge hold release state: V

Figure 6. Quick (supplemental) charge ranges

Quick charge

restart

(0.225 × V

MXT

TEMP

Quick charge

mode

(0.25 × V

HTS

)

mode

TEMP

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V Invalid Time

SM6780AS

−∆

Generally, the battery voltage becomes unstable just after quick charging starts, so the −∆ V battery voltage detection is disabled for 5 minutes to avoid error in battery voltage detection. However, the ∆ T/ ∆t

−∆V Detection (BATT)

After Ni-Cd and Ni-MH batteries are fully charged in quick charge mode, the battery voltage begins to drop after reaching a peak value. The SM6780AS monitors the delta voltage (−∆V) to help determine when the battery is fully charged. When the voltage has fallen a minimum of 8mV (typ), the battery is fully charged and quick charge mode terminates.

Note that −∆V detection is disabled for 5 minutes when quick charge mode is ﬁrst started to avoid error in battery voltage detection, as described in the previous section.

∆T/∆t Detection (TEMP)

When Ni-Cd and Ni-MH batteries are close to full charge in quick charge mode, the temperature of the battery begins to greatly increase. The SM6780AS monitors the temperature change rate (∆V/∆t) to help determine when the battery is fully charged. When the temperature voltage on TEMP decreases by a

temperature detection function continues to operate. After the −∆V detection is enabled, both detection functions operate.

8mV

Vpeak

Cell voltage

Quick charge time

− ∆V detect

Figure 7. Battery voltage change

minimum of 25mV (typ) within a 60-second interval, the battery is considered to be fully charged and quick charge mode terminates.

Note that the TEMP voltage decreases with increasing temperature due to the negative temperature coefﬁcient of the thermistor.

Cell voltage

Cell temperature

Voltage

Quick charge time

Figure 8. Battery temperature change

Voltage

Cell voltage

25mV

Quick charge time

Figure 9. V

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TEMP

∆t

60s

∆T/∆t detect

change

∆T

TEMP

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Maximum Charging Time (TIME)

SM6780AS

The SM6780AS supports 3 different maximum charging time settings, in quick charge and supplemental charge modes, which can be selected on the 3-level input TIME (HIGH, MID, LOW). HIGH level is achieved by pull-up, LOW level by pull-

VDD = 5V, Ta = 25°C

TIME voltage level

min typ max

HIGH 192 240 288

MID 96 120 144

LOW648096

Quick charge/supplemental charge time (minutes)

Quick (Supplemental) Charge Inhibit (INH)

When INH goes HIGH, quick charge mode or supplemental charge mode operation stops. While INH is HIGH, the internal timer stops and pulse trickle

Standby Mode

When the BATT input voltage is ≥ V SM6780AS is in standby mode. In this mode, the internal timer is reset, and the LEDN and CHGN

STB

, the

down, and MID level by a high-resistance voltage divider arrangement to set the voltage at VDD/2. The voltage level on TIME should only be switched in standby mode.

charging occurs. When INH goes LOW, the charging mode is restored to the previously active mode and the internal timer restarts.

outputs become high impedance. Standby mode is released when the voltage applied to BATT falls below V

STB

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Charging Flow Diagram

Supply applied

Standby mode released

LED ON

SM6780AS

(maximum battery voltage: VBATT ≥ 2V)

(battery temperature: 0.225VDD ≤ VTEMP ≤ 0.4VDD)

continuously battery check operation

Maximum quick charge time count start

Initial timer (5 minutes) count start

− ∆V detection

∆T/∆t detection

maximum charge time passed

Maximum supplemental charge time count start

LEDN = High impedance (OFF)

Battery check

and

− ∆V detection disabled

∆T/∆t detection enabled

Quick charge mode

LEDN = LOW (ON)

CHGN = High impedance

or or

Supplemental mode

CHGN = pulse

Not OK

Battery check OK Maximum battery voltage:

and

battery temperature:

0.25VDD ≤ VTEMP ≤ 0.4VDD

Battery check not OK

VBATT ≥ 2V

Battery out-of-range

Pulse trickle mode charging

LEDN = pulse (flashing)

CHGN = pulse

Maximum charging time passed

Battery check not OK or maximum charging time passed

Charging terminates

Pulse trickle mode charging

LEDN = High impedance (OFF)

CHGN = pulse

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Charging Operating Status

SM6780AS

Conditions

Charging status

INH

Battery

check OK

Charging mode CHGN output

LEDN output Internal timer

Quick charge LOW Yes Quick charge High impedance LOW (ON) Count Quick charge hold LOW No Pulse trickle 13.68Hz, 3.91% duty 1Hz (pulsing) Count

Quick charge inhibit HIGH – Pulse trickle 13.68Hz, 3.91% duty

Same condition as

when INH went HIGH

Hold

Supplemental charge LOW OK Supplemental 218Hz, 6.25% duty High impedance (OFF) Count Supplemental charge inhibit HIGH OK Pulse trickle 13.68Hz, 3.91% duty High impedance (OFF) Hold Pulse trickle – – Pulse trickle 13.68Hz, 3.91% duty High impedance (OFF) – Standby – – – High impedance High impedance (OFF) Reset

1. Frequency and duty are typical values.

TYPICAL APPLICATION CIRCUIT

External current source

VBB 12V

5.1kΩ

2SC945

78L05

VSS

OUT

VBEQ2

Q2 2SD525

R2 4/5W

ICHG

CHG =

5 − V

5 − 0.65

BEQ2

VDD 5V

SW1

1.8kΩ

R3 100kΩ

R4 100kΩ

VDD

LEDN

TIME

VSS

33kΩ

SM6780AS

CHGN

INH

TEMP

BATT

= N − 1

R10

N= Number of cells

R7 100kΩ

Q3 2SC945

200kΩ

R10

200kΩ

SW2

R8 100kΩ

NTC R:10kΩ (at 25 C) B:3435K

R11 640Ω

R12 12kΩ

R13 14kΩ

Note that the above circuit is an example circuit to demonstrate the connections for device functions. Battery charger operation is not guaranteed.

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SM6780AS

NIPPON PRECISION CIRCUITS INC. reserves the right to make changes to the products described in this data sheet in order to improve the design or performance and to supply the best possible products. Nippon Precision Circuits Inc. assumes no responsibility for the use of any circuits shown in this data sheet, conveys no license under any patent or other rights, and makes no claim that the circuits are free from patent infringement. Applications for any devices shown in this data sheet are for illustration only and Nippon Precision Circuits Inc. makes no claim or warr anty that such applications will be suitab le for the use speciﬁed without further testing or modiﬁcation. The products described in this data sheet are not intended to use for the apparatus which inﬂuence human lives due to the failure or malfunction of the products. Customers are requested to comply with applicable laws and regulations in effect now and hereinafter, including compliance with export controls on the distribution or dissemination of the products. Customers shall not expor t, directly or indirectly, any products without ﬁrst obtaining required licenses and approvals from appropriate government agencies.

NIPPON PRECISION CIRCUITS INC. 4-3, Fukuzumi 2-chome

Koto-ku, Tokyo 135-8430, Japan

NIPPON PRECISION CIRCUITS INC.

Telephone: 03-3642-6661 Facsimile: 03-3642-6698

NC9918AE 2000.05

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