6781_nc0026ce

SM6781BV
Ni-MH/Ni-Cd Battery Charger IC
OVERVIEW
The SM6781BV is a quick charge control IC for Nickel Metal Hydride (NiMH) and Nickel-Cadmium (NiCd)
rechargeable batteries. Quick charging ends in response to negative delta voltage detection (–∆V) and maximum charging time detection functions. Also, quick charge mode is placed on hold if the battery voltage
becomes abnormal, until normal conditions are restored. The SM6781BV requires few external components to
realize a high-stability quick charge battery charger.
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■
■
■
■
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Ni-MH/Ni-Cd battery quick charge control
−∆V and maximum charge time cutoffs
15min (typ) −∆V detection invalid time
– 4mV (typ) −∆V detection accuracy
Inhibit function
Charge condition LED indicator output
(on, pulsed, off)
Low power dissipation standby mode (< 1µA)
8-pin VSOP package
(Top view)
TIME
CHGN
LEDN
INH
BATT
NC
SM6781BV
8-pin VSOP
PACKAGE DIMENSIONS
(Unit: mm)
0 to 10 °
4.4 ± 0.2
Package
+ 0.1
.05
0.15 − 0
0.575TYP
3.1 ± 0.3
1.15 ± 0.05
Device
VDD
VSS
ORDERING INFORMATION
0.5 ± 0.2
■
6.4 ± 0.3
■
PINOUT
0.65
0.10
0.1 ± 0.05
FEATURES
0.22 ± 0.1
0.12 M
SEIKO NPC CORPORATION —1
SM6781BV
BLOCK DIAGRAM
VDD
DC
Input
VDD
TIME
CHGN
Current
Source
Reference
Regulators
Timer Mode
Selector
CHG Driver
VDD
BATT
Max/Min
Cell-voltage
Check
A/D
−∆V
Function
Block
Timing Control
Logic
LEDN
Battery
Pack
Charge Control
Logic
INH
SW
LED Driver
OSC
NC
VSS
PIN DESCRIPTION
Number
Name
I/O
Description
1
TIME
I
Timer mode select input (3-level)
HIGH and LOW levels applied using pull-up and pull-down, respectively. MID-level is applied using a
voltage divider resistor network with voltage VDD/2.
2
LEDN
O
Charge status display LED driver output (open-drain output)
LOW-level output in quick charge mode. 1Hz pulse output when abnormal battery voltage is detected
during quick charge or when INH is HIGH. High impedance when charging finishes.
3
BATT
I
Battery voltage detector input.
Connect a high-impedance resistor voltage divider between the poles of the battery for voltage detection.
4
VSS
–
Ground
5
VDD
–
Supply
6
NC
–
No connection (must be open)
7
INH
I
Charge inhibit input
Charging operation is stopped when HIGH. Charging recommences with the same charging parameters
when INH goes LOW again.
8
CHGN
O
Charge control (open-drain output)
High impedance output when charging current is flowing. LOW-level output when charging current stops.
SEIKO NPC CORPORATION —2
SM6781BV
SPECIFICATIONS
Absolute Maximum Ratings
VSS = 0V
Parameter
Symbol
Condition
Rating
Unit
Supply voltage range
VDD
− 0.3 to 7.0
V
Input voltage range
VIN
− 0.3 to 7.0
V
Storage temperature range
Tstg
− 55 to 125
°C
Operating temperature range
Topr
– 25 to 85
°C
Power dissipation
PD
150
mW
DC Characteristics 1
VDD = 4.0 to 5.5V, VSS = 0V, Ta = 25°C
Parameter
Symbol
Condition
Rating
Variation
Unit
Minimum battery voltage
VMNV
VBATT < VMNV quick charge cutoff or
prohibition
0.6
± 0.2
V
Maximum battery voltage
VMXV
VBATT > VMXV quick charge cutoff or
prohibition
2.0
± 0.1
V
DC Characteristics 2
VDD = 4.0 to 5.5V, VSS = 0V, Ta = 0 to 85°C unless otherwise noted.
Rating
Parameter
Symbol
Condition
Unit
min
typ
max
VDD supply voltage
VDD
4.0
5.0
5.5
V
BATT input voltage
VBATT
0
–
VDD
V
INH HIGH-level input voltage
VIH1
VDD − 0.5
–
–
V
INH LOW-level input voltage
VIL1
–
–
0.5
V
TIME HIGH-level input voltage
VIH2
VDD − 0.5
–
–
V
TIME MID-level input voltage
VIM
(VDD/2) − 0.5
–
(VDD/2) + 0.5
V
TIME LOW-level input voltage
VIL2
–
–
0.5
V
BATT −∆V detection voltage
range
VDET
1
–
2
V
LEDN output pulse frequency
fLED
–
1
–
Hz
BATT standby voltage
VSTB
VDD − 1.5
–
VDD − 0.5
V
VDD current consumption
IDD
VDD = 5V, no load
–
–
0.5
mA
VDD standby current
ISTB
VDD = 5V, VBATT = VDD , no load
–
–
1
µA
LEDN, CHGN sink current
IOL
VOL = VSS + 0.8V
10
–
–
mA
INH, TIME input leakage
current
IL
VINH = VTIME = VSS to VDD
–
–
±1
µA
LEDN, CHGN output leakage
current
IOZ
−5
–
–
µA
SEIKO NPC CORPORATION —3
SM6781BV
Maximum Quick Charging Time
VDD = 5V, Ta = 25°C
TIME pin
min
typ
max
Unit
HIGH
192
240
288
min
MIDDLE
96
120
144
min
LOW
64
80
96
min
min
typ
max
Unit
–
–4
–
mV
min
typ
max
Unit
720
900
1080
sec
–∆V Detection Voltage
VDD = 5V, Ta = 25°C
–∆V detection voltage
–∆V detection prohibit time
VDD = 5V, Ta = 25°C
–∆V detection prohibit time
SEIKO NPC CORPORATION —4
SM6781BV
FUNCTIONAL DESCRIPTION
Charging Flowchart
Supply applied
Standby mode released
Initialization (approx. 200ms)
Maximum quick charge time count start
−∆V detection prohibit time count start
Abnormal battery voltage detection
or INH = HIGH
Battery voltage check start
(Abnormal battery voltage detection
at VBATT ≥ 2V or 0.6V > VBATT)
Continuously battery voltage check operation
Maximum quick charge time count stopped
−∆V detection prohibit time count stopped
Quick charge mode
(−∆V detection prohibit condition)
LEDN = LOW (ON)
CHGN = High impedance
Quick charge hold
LEDN = High impedance (pulsing)
CHGN = LOW
Abnormal battery voltage detection
or INH = HIGH
NO
−∆V detection prohibit time passed
YES
Quick charge mode
(−∆V detection active condition)
LEDN = LOW (ON)
CHGN = High impedance
NO
− ∆V detection
or
Maximum quick charge time passed
Abnormal battery voltage
detection cleared
(Return status in force
before abnormal battery
voltage detected)
and INH = LOW
Battery voltage check
(Battery voltage: VBATT ≥ 2V or 0.6V > VBATT)
CHGN = LOW
(Quick charge current stop condition)
YES
NO
INH = HIGH
YES
NO
Peak voltage data clear
YES
Quick charge finished
Battery voltage check stop
LEDN = High impedance (OFF)
CHGN = LOW
Maximum quick charge time count restarted
−∆V detection prohibit time count restarted
Resume quick charge mode
SEIKO NPC CORPORATION —5
SM6781BV
Initialization
The SM6781BV charging operation commences when power is applied or when a battery is inserted (standby
mode released). When initialization finishes, the charging mode is determined by the BATT input voltage and
the timer mode.
Battery Voltage Check
When the BATT input voltage is outside the permitted range, quick charge stops. At this point, the maximum
quick charge time count and -∆V prohibit time counters also stop. When the BATT input voltage comes back
within the permitted range, quick charge and timer stop conditions are resumed approximately 2.3 seconds
after. When quick charge mode is restarted, the saved peak voltage data is reset (cleared to 0V).
–∆V Detection Prohibit Time
–∆V detection is not performed for approximately 15 minutes from when quick charge commences (quick
charge cumulative time).
CHGN Output
CHGN becomes high impedance during quick charge. CHGN goes LOW when quick charge mode finishes,
abnormal battery voltage is detected, or INH is HIGH.
Hi-Z
CHGN
Low
Quick charge
Stop/Hold/INH=High
Figure 1. CHGN state
LEDN Output
LEDN is LOW during quick charge (LED is ON), and high impedance after quick charge finishes (LED is
OFF). When an abnormal battery voltage is detected before quick charge finishes, a pulse of approximately
1Hz is output (LED flashes). Also, a 1Hz pulse is output when INH is HIGH.
Hi-Z
LEDN
Low
Quick charge
Abnormal battery
voltage detect
Stop/Hold,
INH = High
Figure 2. LEDN state
Quick Charge Termination
Quick charge finishes when either –∆V voltage is detected or the maximum charging time has elapsed.
SEIKO NPC CORPORATION —6
SM6781BV
–∆V Detection Function
A –∆V condition is detected when the BATT voltage (VBATT) falls 4mV (typ) or more below the peak battery
voltage, at which point the battery is deemed to be fully charged and quick charge finishes (valid for 1V <
VBATT < 2V).
4mV
Cell voltage
Vpeak
− ∆V detect
Quick charge time
Figure 3. Battery voltage change
–∆V Detection A/D Converter
The A/D converter employs dual slope A/D conversion, and converts samples taken approximately every 2.34
seconds.
–∆V Detection Timing
The –∆V detection and peak voltage detection are determined by the average value of 8 A/D converted samples. Consequently, –∆V detection timing occurs approximately every 18 seconds (8-sample length).
490ms max
8
2
1
7
3
8
Operation
A/D convert
Stop
2.34sec
Averaging
− ∆V detect
Peak hold
and compare
18sec
Peak hold
and compare
Figure 4. –∆V detection and A/D convert
Standby Mode
When the BATT input voltage exceeds the standby voltage VSTB, the device enters standby mode.
In this mode, the maximum quick charging time timer, –∆V detection prohibit timer, and peak voltage data are
all reset to zero. At this time, the CHGN and LEDN outputs both become high impedance.
Charge Inhibit (INH)
When INH goes HIGH, charge mode operation stops. While INH is HIGH, the internal timer stops, CHGN
goes LOW and LEDN outputs 1Hz pulse (LEDN flashes). When INH goes LOW, the SM6781BV is restored to
the previous state and the internal timer restarts. Note that the saved peak voltage data (– ∆V) is reset (cleared
to 0V).
If INH is connected to temperature switch (NPC SM6611), it realizes simple temperature control.
SEIKO NPC CORPORATION —7
SM6781BV
BATT Input
The voltage applied to the BATT input, used for battery voltage detection, is a voltage potential, derived by a
voltage divider resistor network (100kΩ or higher recommended) or other means, that represents the voltage of
a single battery cell during charging. If a single cell only is under charge, a current limiting resistor (100kΩ or
higher is recommended) should be connected between the battery and BATT input.
Current
Source
Current
Source
BATT pin
Ra
100kΩ
N
BATT pin
Rb
Ra
=N−1
Rb
N:Number of cells
Figure 5. BATT connection example (multiple)
Figure 6. BATT connection example (single)
Operating Mode vs. BATT Input Voltage
Battery voltage
[V]
Battery
check
Quick
charge
−∆V
detect
Standby
mode
VDD
Valid
VDD − 0.5
VDD − 1.5
NG
2.0
Valid
Valid
1.0
0.6
NG
0
Charging Operating Status
Conditions
Charging status
Battery
check OK
CHGN output
LEDN output
Internal timer
INH
Quick charge
LOW
Yes
High impedance
LOW (ON)
Count
Quick charge hold
LOW
No
LOW
1Hz (pulsing)
Hold
Quick charge inhibit
HIGH
–
LOW
1Hz (pulsing)
Hold
Quick charge finish
LOW
Yes
LOW
High impedance (OFF)
Reset
–
–
High impedance
High impedance (OFF)
Reset
Standby
SEIKO NPC CORPORATION —8
SM6781BV
TYPICAL APPLICATION CIRCUIT
(2 cells)
VBB 12V
R1
5.1kΩ
78L05
Q1
2SC945
IN
OUT
VSS
5V
VBEQ2
Q2
2SD525
ICHG =
R2
4Ω5W
=
5 − VBEQ2
R2
5 − 0.65
4
ICHG
VDD 5V
R6
33kΩ
R5
1.8kΩ
Q3
2SC945
R7
100kΩ
CPU
or
Temperature switch
(SM6611)
SM6781BV
5
R3
100kΩ
SW1
R4
100kΩ
2
1
4
VDD
CHGN
LEDN
INH
TIME
NC
VSS
BATT
8
7
6
3
R8
200kΩ
C1
1000pF
R9
200kΩ
R8
=N−1
R9
N= Number of cells
Note that the above circuit is an example circuit to demonstrate the connections for device functions. Battery
charger operation is not guaranteed.
SEIKO NPC CORPORATION —9
SM6781BV
Please pay your attention to the following points at time of using the products shown in this document.
The products shown in this document (hereinafter “Products”) are not intended to be used for the apparatus that exerts harmful influence on
human lives due to the defects, failure or malfunction of the Products. Customers are requested to obtain prior written agreement for such
use from SEIKO NPC CORPORATION (hereinafter “NPC”). Customers shall be solely responsible for, and indemnify and hold NPC free and
harmless from, any and all claims, damages, losses, expenses or lawsuits, due to such use without such agreement. NPC reserves the right
to change the specifications of the Products in order to improve the characteristic or reliability thereof. NPC makes no claim or warranty that
the contents described in this document dose not infringe any intellectual property right or other similar right owned by third parties.
Therefore, NPC shall not be responsible for such problems, even if the use is in accordance with the descriptions provided in this document.
Any descriptions including applications, circuits, and the parameters of the Products in this document are for reference to use the Products,
and shall not be guaranteed free from defect, inapplicability to the design for the mass-production products without further testing or
modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any entity not in
compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are requested
appropriately take steps to obtain required permissions or approvals from appropriate government agencies.
SEIKO NPC CORPORATION
1-9-9, Hatchobori, Chuo-ku,
Tokyo 104-0032, Japan
Telephone: +81-3-5541-6501
Facsimile: +81-3-5541-6510
http://www.npc.co.jp/
Email: [email protected]
NC0026CE
2006.04
SEIKO NPC CORPORATION —10