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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.
FEATURES
I I I I I I
PINOUT
(Top view)
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 (< 1A) 8-pin VSOP package
TIME LEDN BATT VSS
CHGN INH NC VDD
ORDERING INFORMATION
Device SM6781BV Package 8-pin VSOP
PACKAGE DIMENSIONS
(Unit: mm)
0 to 10
4.4 0.2
6.4 0.3
0.575 typ 3.1 0.3 1.15 0.05
0.15 -0.05
+0.1
0.10
0.22 0.1
0.1 0.05
0.65
0.12 M
NIPPON PRECISION CIRCUITS INC.--1
0.5 0.2
SM6781BV
BLOCK DIAGRAM
VDD
DC Input
VDD
TIME
Current Source
CHGN Reference Regulators Timer Mode Selector CHG Driver BATT Max/Min Cell-voltage Check -V Function Block Timing Control Logic VDD
A/D
LEDN Battery Pack INH SW OSC Charge Control Logic LED Driver
NC VSS
PIN DESCRIPTION
Number 1 Name TIME I/O I 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 or when INH is HIGH. 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. Ground Supply No connection (must be open) Charge 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.
2
LEDN
O
3 4 5 6 7
BATT VSS VDD NC INH
I - - - I
8
CHGN
O
NIPPON PRECISION CIRCUITS INC.--2
SM6781BV
SPECIFICATIONS
Absolute Maximum Ratings
VSS = 0V
Parameter Supply voltage range Input voltage range Storage temperature range Operating temperature range Power dissipation Symbol VDD VIN Tstg Topr PD Condition Rating - 0.3 to 7.0 - 0.3 to 7.0 - 55 to 125 - 25 to 85 150 Unit V V C C mW
DC Characteristics 1
VDD = 4.0 to 5.5V, VSS = 0V, Ta = 25C
Parameter Minimum battery voltage Maximum battery voltage Symbol VMNV VMXV Condition VBATT < VMNV quick charge cutoff or prohibition VBATT > VMXV quick charge cutoff or prohibition Rating 0.6 2.0 Variation 0.2 0.1 Unit V V
DC Characteristics 2
VDD = 4.0 to 5.5V, VSS = 0V, Ta = 0 to 85C unless otherwise noted
Rating Parameter VDD supply voltage BATT input voltage 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 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 Symbol VDD VBATT VIH1 VIL1 VIH2 VIM VIL2 VDET fLED VSTB IDD ISTB IOL IL IOZ VDD = 5V, no load VDD = 5V, VBATT = VDD , no load VOL = VSS + 0.8V VINH = VTIME = VSS to VDD Condition min 4.0 0 VDD - 0.5 - VDD - 0.5 (VDD/2) - 0.5 - 1 - VDD - 1.5 - - 10 - -5 typ 5.0 - - - - - - - 1 - - - - - - max 5.5 VDD - 0.5 - (VDD/2) + 0.5 0.5 2 - VDD - 0.5 0.5 1 - 1 - V V V V V V V V Hz V mA A mA A A Unit
NIPPON PRECISION CIRCUITS INC.--3
SM6781BV
Maximum Quick Charging Time
VDD = 5V, Ta = 25C
TIME pin HIGH MIDDLE LOW min 192 96 64 typ 240 120 80 max 288 144 96 Unit min min min
-V Detection Voltage
VDD = 5V, Ta = 25C
min -V detection voltage - typ -4 max - Unit mV
-V detection prohibit time
VDD = 5V, Ta = 25C
min -V detection prohibit time 720 typ 900 max 1080 Unit sec
NIPPON PRECISION CIRCUITS INC.--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 Battery voltage check start (Abnormal battery voltage detection at VBATT 2V or 0.6V > VBATT) Continuously battery voltage check operation
Abnormal battery voltage detection or INH = HIGH
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 Abnormal battery voltage detection or INH = HIGH
Quick charge hold LEDN = High impedance (pulsing) CHGN = LOW
NO
-V detection prohibit 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
YES
NO
Quick charge mode (-V detection active condition) LEDN = LOW (ON) CHGN = High impedance
INH = HIGH
YES
NO
- V detection or Maximum quick charge time passed
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
NIPPON PRECISION CIRCUITS INC.--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 Figure 2. LEDN state Stop/Hold, INH = High
Quick Charge Termination
Quick charge finishes when either -V voltage is detected or the maximum charging time has elapsed.
NIPPON PRECISION CIRCUITS INC.--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 Vpeak
Cell voltage
Quick charge time
- V detect
Figure 3. Battery voltage change
-V Detection A/D Converter
The A/D converter employs double integration 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 A/D convert Stop 2.34sec Averaging - V detect Peak hold and compare 18sec Peak hold and compare 1 2 3 7 8 Operation
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.
NIPPON PRECISION CIRCUITS INC.--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 (100k 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 (100k or higher is recommended) should be connected between the battery and BATT input.
Current Source
Current Source
Ra N Rb 100k BATT pin Ra =N-1 Rb N:Number of cells
BATT pin
Figure 5. BATT connection example (multiple)
Figure 6. BATT connection example (single)
Operating Mode vs. BATT Input Voltage
Battery voltage [V] VDD Valid VDD - 0.5 VDD - 1.5 Battery check Quick charge -V detect Standby mode
NG 2.0 Valid 1.0 0.6 NG 0 Valid
Charging Operating Status
Conditions Charging status INH Quick charge Quick charge hold Quick charge inhibit Quick charge finish Standby LOW LOW HIGH LOW - Battery check OK Yes No - Yes - CHGN output LEDN output Internal timer
High impedance LOW LOW LOW High impedance
LOW (ON) 1Hz (pulsing) 1Hz (pulsing) High impedance (OFF) High impedance (OFF)
Count Hold Hold Reset Reset
NIPPON PRECISION CIRCUITS INC.--8
SM6781BV
TYPICAL APPLICATION CIRCUIT
(2 cells)
VBB 12V R1 5.1k Q1 2SC945 IN
78L05
OUT VSS 5V VBEQ2 Q2 2SD525 R2 45W ICHG ICHG = = 5 - VBEQ2 R2 5 - 0.65 4
VDD 5V
R6 33k R5 1.8k R7 100k
8 7 6 3
Q3 2SC945
SM6781BV
5
VDD LEDN TIME VSS
CHGN INH NC BATT
CPU or Temperature switch (SM6611)
R3 100k SW1 R4 100k
2 1 4
R8 200k R9 200k
C1 1000pF
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.
NIPPON PRECISION CIRCUITS INC.--9
SM6781BV
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 warranty that such applications will be suitable 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 export, 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 Telephone: +81-3-3642-6661 Facsimile: +81-3-3642-6698 http://www.npc.co.jp/ Email: sales@npc.co.jp
NC0026BE 2001.12
NIPPON PRECISION CIRCUITS INC.--10

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