SM6781BV
NIPPON PRECISION CIRCUITS INC.
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 maxi-
mum 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.
FEATURES
I
I
I
I
I
I
PINOUT
(Top view)
ina
TIME
LEDN
BATT
VSS
I
I
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 (< 1
µ
A)
8-pin VSOP package
ORDERING INFORMATION
Device
SM6781BV
lim
8-pin VSOP
Package
PACKAGE DIMENSIONS
(Unit: mm)
pre
ry
CHGN
INH
NC
VDD
TBD
NIPPON PRECISION CIRCUITS—1
SM6781BV
BLOCK DIAGRAM
VDD
DC
Input
Current
Source
Reference
Regulators
BATT
Max/Min
Cell-voltage
Check
Battery
Pack
−∆V
Function
Block
A/D
ina
Charge Control
Logic
LED Driver
VSS
INH
OSC
Number
1
Name
TIME
lim
I/O
I
O
I
–
Ground
–
Supply
–
I
No connection (must be open)
O
PIN DESCRIPTION
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.
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. High impedance when charging finishes.
Battery voltage detector input.
Connect a high-impedance resistor voltage divider between the poles of the battery for voltage detection.
2
LEDN
3
4
5
6
7
BATT
VSS
pre
NC
INH
8
CHGN
VDD
Inhibit input
Charging operation is stopped when HIGH. Charging recommences with the same charging parameters
when INH goes LOW again.
Charge control (open-drain output)
High impedance output when charging current is flowing. LOW-level output when charging current stops.
ry
CHGN
Timer Mode
Selector
CHG Driver
Timing Control
Logic
LEDN
NC
VDD
TIME
VDD
Description
NIPPON PRECISION CIRCUITS—2
SM6781BV
SPECIFICATIONS
Absolute Maximum Ratings
V
SS
= 0V
Parameter
Supply voltage range
Input voltage range
Storage temperature range
Operating temperature range
Power dissipation
Symbol
V
DD
V
IN
T
stg
T
opr
P
D
Condition
Rating
−
0.3 to 7.0
−
0.3 to 7.0
Unit
V
V
V
DD
= 4.0 to 5.5V, V
SS
= 0V, Ta = 25
°
C
Parameter
Minimum battery voltage
Maximum battery voltage
Symbol
V
MNV
V
MXV
ina
Condition
Rating
0.6
2.0
Rating
Condition
min
4.0
0
0.7
–
V
DD
−
0.5
(V
DD
/2)
−
0.5
–
1
–
V
DD
−
1.5
–
–
10
–
−
5
typ
5.0
–
–
–
–
–
–
–
1
–
–
–
–
–
–
DC Characteristics 1
V
BATT
< V
MNV
charge cutoff or prohibition
V
BATT
> V
MXV
charge cutoff or prohibition
ry
−
55 to 125
– 25 to 85
150
Variation
± 0.2
± 0.1
max
5.5
V
DD
–
0.1
–
(V
DD
/2) + 0.5
0.5
2
–
V
DD
−
0.5
0.5
1
–
±1
–
V
DD
= 5V, no load
V
DD
= 5V, V
BATT
= V
DD
, no load
V
OL
= V
SS
+ 0.8V
V
INH
= V
TIME
= V
SS
to V
DD
°
C
°
C
mW
Unit
V
V
DC Characteristics 2
V
DD
= 4.0 to 5.5V, V
SS
= 0V, Ta = 0 to 85
°
C unless otherwise noted
Parameter
VDD supply voltage
BATT input voltage
lim
Symbol
V
DD
V
BATT
V
IH1
V
IL1
V
IH2
V
IM
V
IL2
V
DET
f
LED
V
STB
I
DD
I
STB
I
OL
I
L
I
OZ
Unit
V
V
V
V
V
V
V
V
Hz
V
mA
µA
mA
µA
µA
INH HIGH-level input voltage
INH LOW-level input voltage
TIME HIGH-level input voltage
TIME MID-level input voltage
TIME LOW-level input voltage
BATT
−∆
V detection voltage
range
pre
LEDN output pulse frequency
BATT standby voltage
VDD current consumption
VDD standby current
LEDN, CHGN sink current
INH, TIME input leakage
current
LEDN, CHGN output leakage
current
NIPPON PRECISION CIRCUITS—3
SM6781BV
Maximum Quick Charging Time
V
DD
= 5V, Ta = 25
°
C
TIME pin
HIGH
MIDDLE
LOW
min
192
96
64
typ
240
120
80
max
288
144
96
Unit
min
min
–
∆
V Detection Voltage
V
DD
= 5V, Ta = 25
°
C
min
–
∆
V detection voltage
–
typ
–4
max
–
–
∆
V detection prohibit time
V
DD
= 5V, Ta = 25
°
C
min
–
∆
V detection prohibit time
720
900
pre
NIPPON PRECISION CIRCUITS—4
lim
ina
mV
typ
max
Unit
sec
1080
ry
min
Unit
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
Battery voltage check start
(Abnormal battery voltage detection
at V
BATT
≥
2V or 0.6V > V
BATT
)
Continuously battery voltage check operation
Quick charge mode
(−∆V detection prohibit condition)
LEDN = LOW (ON)
CHGN = High impedance
Abnormal battery voltage detection
NO
−∆V
detection prohibit time passed
ina
Abnormal battery voltage
detection cleared
(Return status in force
before abnormal battery
voltage detected)
NO
Peak voltage data clear
Abnormal battery voltage
detection cleared
YES
Quick charge mode
(−∆V detection active condition)
LEDN = LOW (ON)
CHGN = High impedance
lim
YES
NO
− ∆V
detection
or
Maximum quick charge time passed
pre
NIPPON PRECISION CIRCUITS—5
Quick charge finished
Battery voltage check stop
LEDN = High impedance (OFF)
CHGN = LOW
ry
Abnormal battery voltage detection
Maximum quick charge time count stopped
−∆V
detection prohibit time count stopped
Quick charge hold
LEDN = High impedance (pulsing)
CHGN = LOW
Battery voltage check
(Battery voltage: V
BATT
≥
2V or 0.6V > V
BATT
)
CHGN = LOW
(Quick charge current stop condition)
YES
Maximum quick charge time count restarted
−∆V
detection prohibit time count restarted
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