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SC810
Single Input/Single Mode Single-cell Li-ion Charger
POWER MANAGEMENT Features
Single input charger Constant voltage -- 4.2V, 1% regulation Fast-charge current regulation -- 15% at 70mA, 9% at 700mA Three mode charging -- current regulation, voltage regulation, and thermal limiting Input voltage protection -- 30V Current-limited charging support -- reduces power dissipation in charger IC Instantaneous CC-to-CV transition for faster charging Three termination options -- float-charge, automatic re-charge, or forced re-charge to keep the battery topped-off after termination without float-charging Soft-start reduces adapter load transients High operating voltage range permits use of unregulated adapters Complies with CCSA YD/T 1591-2006 Space saving 2x2x0.6 (mm) MLPD package WEEE and RoHS compliant
Description
The SC810 is a linear single-cell Li-ion battery charger in a 6 lead 2x2 MLPD Ultra-thin package. The input will survive sustained input voltage up to 30V to protect against hot plug overshoot and faulty charging adapters. Charging begins automatically when a valid input source is applied. Thermal limiting protects the SC810 from excessive power dissipation. It can be programmed to turn off when charging is complete or to continue operating as an LDO regulator while float-charging the battery. The input will charge with an adapter operating in voltage regulation or in current-limit to obtain the lowest possible power dissipation by pulling the input voltage down to the battery voltage. The maximum fast-charge current setting is 1A. Charge current is programmed with a single resistor. Precharge and termination current are fixed at 20% and 10%, respectively, of the programmed fast-charge current. Charge current steps up to the programmed value (soft starts) to reduce load transients on the charging adapter.
Applications
Mobile phones MP3 players GPS handheld receivers
Typical Application Circuit
SC810
VADAPTER VIN STATB GND 2.2 F ENB BAT IPRGM 2.2 F Device Load
Battery Pack
February 26, 2008
(c) 2008 Semtech Corporation
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SC810
Pin Configuration Ordering Information
Device
SC810ULTRT(1)(2) SC810EVB
VIN 1 TOP VIEW 6 ENB
Package
MLPD-UT-6 2x2 Evaluation Board
Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Lead-free package only. Device is WEEE and RoHS compliant.
STATB
2
5
BAT
T
GND
3
4
IPRGM
MLPD-UT6; 2x2, 6 LEAD JA = 68C/W
Marking Information
810 yw
yw = Date Code
(c) 2008 Semtech Corporation
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SC810
Absolute Maximum Ratings
VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +30.0 BAT, IPRGM (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.5 STATB, ENB (V) . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to VBAT + 0.3 VIN Input Current (A). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 BAT, IPRGM Short-to-Duration . . . . . . . . . . . . . Continuous Total Power Dissipation (W) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Recommended Operating Conditions
Operating Ambient Temperature (C) . . . . . . . . . -40 to +85
Thermal Information
Thermal Resistance, Junction to Ambient(2) (C/W). . . . . 68 Junction Temperature Range (C) . . . . . . . . . . . . . . . . . . +150 Storage Temperature Range (C) . . . . . . . . . . . . -65 to +150 Peak IR Reflow Temperature (10s to 30s) (C) . . . . . . . +260
Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. NOTES: (1) Tested according to JEDEC standard JESD22-A114-B. (2) Calculated from package in still air, mounted to 3 x 4.5 (in), 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
Electrical Characteristics
Test Conditions: VVIN= 4.75V to 5.25V; VBAT = 3.7V; Typ values at 25C; Min and Max at -40C < TA < 85C, unless specified.
Parameter
VIN Operating Voltage (1) VIN Under-Voltage Lockout Rising Threshold VIN Under-Voltage Lockout Falling Threshold (2) VIN OVP Rising Threshold VIN OVP Falling Threshold VIN OVP Hysteresis VIN Charging Disabled Quiescent Current VIN Charging Enabled Quiescent Current CV Regulation Voltage CV Voltage Load Regulation
Symbol
VOP VTUVLO-R VTUVLO-F VTOVP-R VTOVP-F VTOVP-H IqVIN_DIS IqVIN_EN VCV VCV_LOAD lBAT_V0
Conditions
Min
4.60 4.30
Typ
5.00 4.45 2.85
Max
8.20 4.60 3.00 9.6
Units
V V V V V mV
VVIN > VBAT
2.70
8.2 VTOVP-R - VTOVP-F VENB = VBAT VENB = 0V, excluding IBAT and IIPRGM IBAT = 50mA, -40C TJ 125C Relative to VCV @ 50mA, 1mA IBAT 1A, -40C TJ 125C VVIN = 0V VVIN = 5V, VENB = 2V VVIN = 5V, VBAT = VCV, ENB not connected VCV - VBAT 60 2.85 4.16 -20 0.1 0.1 0.1 100 2.90 50 2 2 4.20 3 3 4.24 10 1 1 1 140 2.95
mA mA V mV A A A mV V
Battery Leakage Current
lBAT_DIS lBAT_MON
Re-charge Threshold Pre-charge Threshold (rising)
VTReQ VTPreQ
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SC810
Electrical Characteristics (continued)
Parameter
IPRGM Programming Resistor Fast-Charge Current, adapter mode Pre-Charge Current Termination Current Dropout Voltage IPRGM Fast-charge Regulated Voltage IPRGM Pre-charge Regulated Voltage IPRGM Termination Threshold Voltage Thermal Limiting Threshold Temperature Thermal Limiting Rate ENB Input High Voltage ENB Input Mid Voltage ENB Input Low Voltage ENB Input High-range Threshold Input Current ENB Input High-range Sustain Input Current ENB Input Mid-range Load Limit ENB Input Low-range Input Current ENB Input Leakage STATB Output Low Voltage STATB Output High Current
Symbol
RIPRGM IFQ_AD IPreQ ITERM VDO VIPRGM_FQ VIPRGM_PQ VTIPRGM_TERM T TL iT VIH VIM VIL IIH_TH
Conditions
Min
2.05
Typ
Max
29.4
Units
k mA mA mA V V V V C mA/ C V
RIPRGM = 2.94k, VTPreQ < VBAT < VCV RIPRGM = 2.94k, 1.8V < VBAT < VTPreQ RIPRGM = 2.94k, VBAT = VCV IBAT = 700mA, 0C TJ 125C VVIN = 5.0V, VTPreQ < VBAT < VCV 1.8V < VBAT < VTPreQ VBAT = VCV (either input selected)
643 105 59
694 139 69 0.40 2.04 0.408 0.204 130 50
745 173 80 0.60
1.6 0.7 1.3 0.3 ENB current required to pull ENB from floating midrange into high range Current required to hold ENB in high range, Min VIH VENB VBAT, Min VIH VBAT 4.2V Input will float to mid range when this load limit is observed. 0V VENB Max VIL VVIN = 0V, VENB = VBAT = 4.2V ISTAT_SINK = 2mA VSTAT = 5V -5 -25 -12 1 0.5 1 23 50
V V A
IIH_SUS
0.3
1
A
IIM IIL IILEAK VSTAT_LO ISTAT_HI
5
A A A V A
Notes: (1) Maximum operating voltage is the maximum Vsupply as defined in EIA/JEDEC Standard No. 78, paragraph 2.11. This is the input voltage at which the charger is guaranteed to begin operation. (2) Sustained operation to VTUVLO-F VVIN is guaranteed only if a current limited charging source applied to VIN is pulled below VTUVLO-R by the charging load; forced VIN voltage below VTUVLO-R in some cases may result in regulation errors or other unexpected behavior.
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SC810
Typical Characteristics
CV Line Regulation
TA = 25 C, IBAT = 50mA 4.204 4.204

CV Load Regulation
TA = 25 C, VVIN = 5V
4.2
4.2
4.196
4.196
VBAT (V)
VBAT (V)
4.192
4.192
4.188
4.188
4.184
4.184
4.18
5
5.5
6
6.5
7
7.5
8
4.18 0
100
200
300
400
500
600
700
800
VVIN (V)
IBAT (mA)
CV Temperature Regulation
VVIN = 5V, IBAT = 50mA 4.204 720
CC FQ Line Regulation
TA = 25 C, VBAT = 3.7V, RIPRGM = 2.94k
4.2
716
4.196
712
4.192
IBAT (mA)
-40 -20 0 20 40 60
o
VBAT (V)
708
4.188
704
4.184
700
4.18
80
100
120
696 4.5
5
5.5
6
6.5
7
7.5
8
Ambient Temperature ( C)
VVIN (V)
CC FQ VBAT Regulation
TA = 25 C, VVIN = 5V, RIPRGM = 2.94k 720 720
CC FQ Temperature Regulation
VVIN = 5V, VBAT = 3.7V, RIPRGM = 2.94k
716
716
712
712
IBAT (mA)
708
IBAT (mA)
3.1 3.3 3.5 3.7 3.9 4.1
708
704
704
700
700
696 2.9
696
-40
-20
0
20
40
60
o
80
100
120
VBAT (V)
Ambient Temperature ( C)
(c) 2008 Semtech Corporation
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SC810
Typical Characteristics (continued)
CC PQ Line Regulation
TA = 25 C, VBAT = 2.6V, RIPRGM = 2.94k 160 160
CC PQ Temperature Regulation
VVIN = 5V, VBAT = 2.6V, RIPRGM = 2.94k
156
156
IBAT (mA)
IBAT (mA)
152
152
148
148
144
144
140
5
5.5
6
6.5
7
7.5
8
140
-40
-20
0
20
40
60
o
80
100
120
VVIN (V)
Ambient Temperature ( C)
FQ VVIN = 5V, VBAT = 3.7V, TA = 25 C
1000
I vs. RIPRGM
200
PQ VVIN = 5V, VBAT = 2.6V, TA = 25 C
I vs. RIPRGM
800
160
IBAT (mA)
600
IBAT (mA)
6 10 14 18 22 26 30
120
400
80
200
40
0 2
0 2
6
10
14
18
22
26
30
RIPRGM (k)
RIPRGM (k)
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SC810
Typical Characteristics (continued)
Charging Cycle Battery Voltage and Current
850mAhr battery, RIPRGM = 2.94k, VVIN = 5.0V, TA = 25 C 4
Pre-Charging Battery Voltage and Current
850mAhr battery, RIPRGM = 2.94k, VVIN = 5.0V, TA = 25 C 800 700 IBAT 3.5 600 500 400 VBAT 2.75 2.5 2.25 2 0 300 200 100 0 20 700 3.75 600 500
VBAT (V), Internal Power Dissipation (W)
7 6 5 VBAT 4 3 2 1 0 0 IBAT
IBAT (mA)
3.25
400 300 200 100 0 2.25
3
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2
4
6
8
10
12
14
16
18
Time (hrs)
Time (s)
CC-to-CV Battery Voltage and Current
850mAhr battery, RIPRGM = 2.94k, VVIN = 5.0V, TA = 25 C 4.21 710
Re-Charge Cycle Battery Voltage and Current
850mAhr battery, RIPRGM = 2.94k, VVIN = 5.0V, Load = 10mA 4.5 450 VBAT 400 350 300 250 200 150 IBAT 100 50 Discharge hours 2 - 6 omitted. 0 7.5
VBAT (V), Internal Power Dissipation (W)
4.2
IBAT
4 3.5 3 2.5 2 1.5 1 0.5 0 0.0
690
IBAT (mA)
4.18 VBAT 4.17
650
630
4.16 44
44.5
45
45.5
46
46.5
47
47.5
610 48
0.5
1.0
1.5
2/6
6.5
7.0
Time (min)
Time (hrs)
(c) 2008 Semtech Corporation
IBAT (mA)
VBAT (V)
4.19
670
IBAT (mA)
VBAT (V)
7
SC810
Pin Descriptions
Pin #
1
Pin Name
VIN
Pin Function
Supply pin -- connect to charging adapter (wall adapter or USB). This is a high voltage (30V) pin. Status output pin -- This open-drain pin is asserted (pulled low) when a valid charging supply is connected to VIN, and a charging cycle begins. It is released when the termination current is reached, indicating that charging is complete. STATB is not asserted for re-charge cycles. Ground Fast-charge and pre-charge current programming pin -- Fast-charge current is programmed by connecting a resistor from this pin to ground. Pre-charge current is 20% of fast-charge current. The charging termination current threshold is 10% of the IPRGM programmed fast-charge current. Charger output -- connect to battery positive terminal. Combined device enable/disable -- Logic high disables the device. Tie to GND to enable charging with indefinite float-charging. Float this pin to enable charging without float-charge upon termination. Note that this pin must be grounded if the SC810 is to be operated without a battery connected to BAT. Pad is for heat sinking purposes -- not connected internally. Connect exposed pad to ground plane using multiple vias.
2
STATB
3
GND
4
IPRGM
5
BAT
6
ENB
T
Thermal Pad
(c) 2008 Semtech Corporation
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SC810
Block Diagram
V_Adapter
1
VIN
Connect to BAT or to regulated supply
VCV = 4.2V
CV
VIREF
CC BAT
To System Load
5
Die Temperature VT_CT Thermal Limiting LithiumIon Single Cell Battery Pack
2
STATB Precharg, CC/CV & Termination Controller, Logical State Machine
Termination VTIPRGM_TERM VTENB_HIGH = ~1.50V
1V
Tri-level Control
VTENB_LOW = ~0.55 IPRGM
ENB
GND
6
RIPRGM
4
3
(c) 2008 Semtech Corporation
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SC810
Applications Information
Charger Operation
The SC810 is a single cell Li-ion battery charger. It implements a Constant Current, Constant Voltage, Constant Temperature (CC/CV/CT) charging algorithm. When an input supply is first detected, a charge cycle is initiated and the STATB open-drain output goes low. If the battery voltage is less than the pre-charge threshold voltage, the pre-charge current is supplied. Pre-charge current is 20% of the programmed fast-charge current. When the battery voltage exceeds the pre-charge threshold, typically within seconds for a standard battery with a starting cell voltage greater than 2V, the fast-charge Constant Current (CC) mode begins. The charge current soft-starts in three steps (20%, 60%, and 100% of programmed fast-charge current) to reduce adapter load transients. CC current is programmed by the IPRGM resistance to ground. The charger begins Constant Voltage (CV) regulation when the battery voltage rises to the fully-charged singlecell Li-ion regulation voltage (VCV ), nominally 4.2V. In CV regulation, the output voltage is regulated, and as the battery charges, the charge current gradually decreases. The STATB output goes high when IBAT drops below the termination current threshold, which is 10% of the IPRGM pin programmed fast-charge current, regardless of the mode selected. This is known as charge termination. (UVLO) threshold will not be recognized until the ringing has ceased. The UVLO rising threshold is set higher than the voltage of a fully charged Li-ion single cell battery, ensuring that only a charging source capable of fully charging the battery has been applied. If the charging current loads the adapter beyond its current limit, the input voltage will be pulled down to just above the battery voltage. The UVLO falling threshold is set close to the battery voltage pre-charge threshold to permit lowdissipation charging from a current limited adapter.
Constant Current Mode Fast-charge Current Programming
The Constant Current (CC) mode is active when the battery voltage is above VTPreQ and less than VCV. The programmed CC regulation fast-charge (FQ) current is inversely proportional to the resistance between IPRGM and GND according to the equation
IFQ VIPRGM _ Typ 1000 RIPRGM
The fast-charge current can be programmed for a minimum of 70mA and a maximum of 995mA, nominally. Current regulation accuracy is dominated by gain error at high current settings, and offset error at low current settings. The range of expected fast-charge output current versus programming resistance is shown in Figures 1a and 1b. The figures show the nominal current versus nominal RIPRGM resistance as the center plot and two theoretical limit plots indicating maximum and minimum current versus nominal programming resistance. These plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. The current range includes the uncertainty due to 1% tolerance resistors. The dots on each plot indicate the currents obtained with standard value 1% tolerance resistors. Figures 1a and 1b show low and high resistance ranges, respectively.
Optional Float-charging or Monitoring
Depending on the state of the ENB input, upon termination the SC810 either operates indefinitely as a voltage regulator (float-charging) or it turns off its output. If the output is turned off upon termination, the device enters the monitor state. In this state, the output remains off until the BAT pin voltage decreases by the re-charge threshold (VTReQ). A re-charge cycle then begins automatically and the process repeats. A forced re-charge cycle can also be periodically commanded by the processor to keep the battery topped-off without float-charging. See the Monitor State section for details. Re-charge cycles are not indicated by the STATB pin.
Pre-charge Mode
This mode is automatically enabled when the battery voltage is below the pre-charge threshold voltage (VTPreQ), typically 2.8V. Pre-charge current conditions the battery for fast charging. The pre-charge current value is
10
Charging Input Pin Properties
Glitch filtering is performed on the VIN pin, so an input voltage that is ringing across its Under-Voltage Lockout
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SC810
Applications Information (continued)
1100 1050 300 1000 950 900 275 250 325
Fast-charge Current (mA)
800 750 700 650 600 550 500 450 400 350
Fast-charge Current (mA)
2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
850
225 200 175 150 125 100 75
300 250 2 50 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
RIPRGM (k), R-tol = 1%
RIPRGM (k), R-tol = 1%
Figure 1a -- Fast-charge Current Tolerance versus Programming Resistance, Low Resistance Range fixed at 20% nominally of the fast-charge current for the selected input, as programmed by the resistance between IPRGM and GND. Pre-charge current regulation accuracy is dominated by offset error. The range of expected pre-charge output current versus programming resistance is shown in Figures 2a and 2b. The figures show the nominal precharge current versus nominal RIPRGM resistance as the center plot and two theoretical limit plots indicating
270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
Figure 1b -- Fast-charge Current Tolerance versus Programming Resistance, High Resistance Range maximum and minimum current versus nominal programming resistance. These plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. The current range includes the uncertainty due to 1% tolerance resistors. The dots on each plot indicate the currents obtained with standard value 1% tolerance resistors. Figures 2a and 2b show low and high resistance ranges, respectively.
80 75 70 65 60
Pre-charge Current (mA)
Pre-charge Current (mA)
55 50 45 40 35 30 25 20 15 10 5 0 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
RIPRGM (k), R-tol = 1%
RIPRGM (k), R-tol = 1%
Figure 2a -- Pre-charge Current Tolerance versus Programming Resistance, Low Resistance Range
Figure 2b -- Pre-charge Current Tolerance versus Programming Resistance, High Resistance Range
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SC810
Applications Information (continued)
Termination
When the battery voltage reaches VCV, the SC810 transitions from constant current regulation to constant voltage regulation. While VBAT is regulated to VCV, the current into the battery decreases as the battery becomes fully charged. When the output current drops below the termination current threshold, fixed at 10% of the programmed fast-charge current, charging terminates. Upon termination, the STATB pin open drain output turns off and the charger either enters monitor state or float-charges the battery, depending on the logical state of the ENB input pin. Charger output current is the sum of the battery charge current and the system load current. Battery charge current changes gradually, and establishes a slowly diminishing lower bound on the output current while charging in CV mode. The load current into a typical digital system is highly transient in nature. Charge cycle termination is detected when the sum of the battery charging current and the greatest load current occurring within the immediate 300s to 550s past interval is less than the programmed termination current. This timing behavior permits charge cycle termination to occur during a brief low-load-current interval, and does not require that the longer interval average load current be small. Termination current threshold accuracy is dominated by offset error. The range of expected termination current
115 110 105 100 30 35
versus programming resistance is shown in Figures 3a and 3b. The figures show the nominal termination current versus nominal RIPRGM resistance as the center plot and two theoretical limit plots indicating maximum and minimum current versus nominal programming resistance. These plots are derived from models of the expected worst-case contribution of error sources depending on programmed current. The current range includes the uncertainty due to a 1% tolerance resistor. The dots on each plot indicate the currents obtained with standard value 1% tolerance resistors. Figures 3a and 3b show low and high resistance ranges, respectively.
Enable Input
The ENB pin is a tri-level logical input that allows selection of the following behaviors: charging enabled with float-charging after termination (ENB = low range) charging enabled with float-charging disabled and battery monitoring at termination (ENB = mid range) charging disabled (ENB = high range). It is designed to interface to a processor GPIO port powered from a peripheral supply voltage as low as 1.8V or as high as a fully charged battery. While a connected GPIO port is configured as an output, the processor writes 0 to select ENB low-range, and 1 to select high-range.
Termination Current Threshold (mA)
95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 0 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 5
Termination Current Threshold (mA)
25
20
15
10
RIPRGM (k), R-tol = 1%
RIPRGM (k), R-tol = 1%
Figure 3a -- Termination Current Tolerance versus Programming Resistance, Low Resistance Range
Figure 3b -- Termination Current Tolerance versus Programming Resistance, High Resistance Range
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SC810
Applications Information (continued)
The GPIO port is configured as an input to select mid-range. ENB can also be permanently grounded to select lowrange or left unconnected to select mid-range if it will not be necessary to change the level selection. The equivalent circuit looking into the ENB pin is a variable resistance, minimum 15k, to an approximately 1V source. The input will float to mid range whenever the external driver sinks or sources less than 5A, a common worst-case characteristic of a high impedance or a weak pull-up or pull-down GPIO configured as an input. The driving GPIO must be able to sink or source at least 75A to ensure a low or high state, respectively, although the drive current is typically far less. (See the Electrical Characteristics table.) If the ENB input voltage is permitted to float to mid-range, the charger is enabled but it will turn off its output following charge termination and will enter the monitor state. This state is explained in the next section. Mid-range can be selected either by floating the input (sourcing or sinking less than 5A) or by being externally forced such that VENB falls within the midrange limits specified in the Electrical Characteristics table. When driven low (VENB < Max VIL), the charger is enabled and will continue to float-charge the battery following termination. If the charger is already in monitor state following a previous termination, it will exit the monitor state and begin float-charging. When ENB is driven high (VENB > Min VIH), the charger is disabled and the ENB input pin enters a high impedance state, suspending tri-level functionality. The specified high level input current IIH is required only until a high level is recognized by the SC810 internal logic. The trilevel float circuitry is then disabled and the ENB input becomes high impedance. Once forced high, the ENB pin will not float to mid range. To restore tri-level operation, the ENB pin must first be pulled down to mid or low range (at least to VENB < Max VIM), then, if desired, released (by reconfiguring the GPIO as an input) to select mid-range. If the ENB GPIO has a weak pull-down when configured as an input, then it is unnecessary to drive ENB low to restore tri-level operation; simply configure the GPIO as an input. When the ENB selection changes from high-range to midor low-range, a new charge cycle begins and STATB goes low. Note that if a GPIO with a weak pull-up input configuration is used, its pull-up current will flow from the GPIO into the ENB pin while it is floating to mid-range. Since the GPIO is driving a 1V equivalent voltage source through a resistance (looking into ENB), this current is small -- possibly less than 1A. Nevertheless, this current is drawn from the GPIO peripheral power supply and, therefore, from the battery after termination. (See the next section, Monitor State.) For this reason, it is preferable that the GPIO chosen to operate the ENB pin should provide a true high impedance (CMOS) configuration or a weak pulldown when configured as an input. When pulled below the float voltage, the ENB pin output current is sourced from VIN, not from the battery.
Monitor State
If the ENB pin is floating, the charger output and STATB pin will turn off and the device will enter the monitor state when a charge cycle is complete. If the battery voltage falls below the re-charge threshold (VCV - VReQ) while in the monitor state, the charger will automatically initiate a recharge cycle. The battery leakage current during monitor state is no more than 1A over temperature and typically less than 0.1A at room temperature. While in the monitor state, the ENB tri-level input pin remains fully active, and although in midrange, is sensitive to both high and low levels. The SC810 can be forced from the monitor state (no float-charging) directly to floatcharging operation by driving ENB low. This operation will turn on the charger output, but will not assert the STATB output. If the ENB pin is again allowed to float to midrange, the charger will remain on only until the output current becomes less than the termination current, and charging terminates. The SC810 turns off its charging output and returns to the monitor state within a millisecond. This forced re-charge behavior is useful for periodically testing the battery state-of-charge and topping-off the battery, without float-charging and without requiring the battery to discharge to the automatic re-charge voltage. ENB should be held low for at least 1ms to ensure a successful forced re-charge.
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SC810
Applications Information (continued)
Forced re-charge can be requested at any time during the charge cycle, or even with no charging source present, with no detrimental effect on charger operation. This allows the host processor to schedule a forced re-charge at any desired interval, without regard to whether a charge cycle is already in progress, or even whether a charging source is present. Forced re-charge will neither assert nor release the STATB output. for a portion of the charge cycle, which increases charge time. In the SC810, a logical transition is implemented from CC to CV to recover the charge current lost due to the soft transition. The controller regulates only current until the output voltage exceeds the transition threshold voltage. It then switches to CV regulation. The transition voltage from CC to CV regulation is typically 5mV higher than the CV regulation voltage, which provides a sharp and clean transition free of chatter between regulation modes. The difference between the transition voltage and the regulation voltage is termed the CC/CV overshoot. While in CV regulation, the output current sense remains active. If the output current exceeds the programmed fast-charge current by 5%, the controller rever ts to current regulation. The logical transition from CC to CV results in the fastest possible charging cycle that is compliant with the specified current and voltage limits of the Li-ion cell. The output current is constant at the CC limit, then decreases abruptly when the output voltage steps from the overshoot voltage to the regulation voltage at the transition to CV control.
Status Output
The STATB pin is an open-drain output. It is asserted (driven low) as charging begins after a valid charging input is applied and the VIN voltage is greater than the input UVLO level and less than the OVP level. STATB is also asserted as charging begins after the ENB input returns to either of the enable voltage ranges (mid or low voltage) from the disable (high voltage) range. STATB is subsequently released when the termination current is reached to indicate end-of-charge, when the ENB input is driven high to disable charging, or when the input voltage is removed. If the battery is already fully charged when a charge cycle is initiated, STATB is asserted, and remains asserted for approximately 750s before being released. The STATB pin is not asserted for automatic re-charge cycles. The STATB pin may be connected to an interrupt input to notify a host controller of the charging status or it can be used as an LED driver.
Thermal Limiting
Device thermal limiting is the third output constraint of the Constant Current, Constant Voltage, "Constant" Temperature (CC/CV/CT) control. This feature permits a higher input OVP threshold, and thus the use of higher voltage or poorly regulated adapters. If high input voltage results in excessive power dissipation, the output current is reduced to prevent overheating of the SC810. The thermal limiting controller reduces the output current by iT 50mA/C for any junction temperature TJ > T TL. When thermal limiting is inactive, TJ = TA + V IFQ JA, where V is the voltage difference between the VIN pin and the BAT pin. However, if TJ computed this way exceeds T TL, then thermal limiting will become active and the thermal limiting regulation junction temperature will be TJTL = TA + V I(TJTL) JA,
Logical CC-to-CV Transition
The SC810 differs from monolithic linear single cell Li-ion chargers that implement a linear transition from CC to CV regulation. The linear transition method uses two simultaneous feedback signals -- output voltage and output current -- to the closed-loop controller. When the output voltage is sufficiently below the CV regulation voltage, the influence of the voltage feedback is negligible and the output current is regulated to the desired current. As the battery voltage approaches the CV regulation voltage (4.2V), the voltage feedback signal begins to influence the control loop, which causes the output current to decrease although the output voltage has not reached 4.2V. The output voltage limit dominates the controller when the battery reaches 4.2V and eventually the controller is entirely in CV regulation. The soft transition effectively reduces the charge current below that which is permitted
(c) 2008 Semtech Corporation
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SC810
Applications Information (continued)
where I(TJTL) = IFQ - iT (TJTL - T TL). Combining these two equations and solving for TJTL, the steady state junction temperature during active thermal limiting is
TA V IFQ iT TTL 1 V iT JA
TJTL
JA
The low UVLO falling threshold (VT UVLO-F) permits the adapter voltage to be pulled down to just above the battery voltage by the charging load whenever the adapter current limit is less than the programmed fastcharge current. The SC810 should be operated with adapter voltage below the rising selection threshold (VT UVLO-R) only if the low input voltage is the result of adapter current limiting. This implies that the VIN voltage first exceeds VTUVLO-R to begin charging, and is subsequently pulled down to just above the battery voltage by the charging load. Interaction of Thermal Limiting and Current Limited Adapter Charging To permit the charge current to be limited by the adapter, it is necessary that the fast-charge current be programmed greater than the maximum adapter current, (IAD-LIM). In this configuration, the CC regulator will operate with its pass device fully on (in saturation, also called "dropout"). The voltage drop from VIN to BAT is determined by the product of the minimum RDS-ON of the pass device multiplied by the adapter supply current. In dropout, the power dissipation in the SC810 is PILIM = (minimum RDS-ON) x (IAD-LIM)2. Since minimum RDS-ON does not vary with battery voltage, dropout power dissipation is constant throughout the CC portion of the charge cycle while the adapter remains in current limit. The SC810 junction temperature will rise above ambient by PILIM x JA. If the device temperature rises to the temperature at which the thermal limiting control loop limits charging current (rather than the current being limited by the adapter), the input voltage will rise to the adapter regulation voltage. The power dissipation will increase so that the thermal limit regulation will further limit charge current. This will keep the adapter in voltage regulation for the remainder of the charge cycle. To ensure that the adapter remains in current limit, the internal device temperature must never rise to T TL. This implies that JA must be kept small enough to ensure that TJ = TA + (PILIM x JA) < T TL.
Although the thermal limiting controller is able to reduce output current to zero, this does not happen in practice. Output current is reduced to I(TJTL), reducing power dissipation such that die temperature equilibrium TJTL is reached. While thermal limiting is active, all charger functions remain active and the charger logical state is preserved.
Operating a Charging Adapter in Current Limit
In high charging current applications, charger power dissipation can be greatly reduced by operating the charging adapter in current limit. The SC810 supports adaptercurrent-limited charging with a low UVLO falling threshold and with internal circuitry designed for low input voltage operation. To operate an adapter in current limit, RIPRGM is chosen such that the programmed fast-charge current IFQ exceeds the current limit of the charging adapter IAD-LIM. Note that if IAD-LIM is less than 20% of IFQ, then the adapter voltage can be pulled down to the battery voltage while the battery voltage is below the pre-charge threshold. In this case, care must be taken to ensure that the adapter will maintain its current limit below 20% of IFQ at least until the battery voltage exceeds the pre-charge threshold. Failure to do so could permit charge current to exceed the pre-charge current while the battery voltage is below the pre-charge threshold. This is because the low input voltage will also compress the pre-charge threshold internal reference voltage to below the battery voltage. This will prematurely advance the charger logic from precharge current regulation to fast-charge regulation, and the charge current will exceed the safe level recommended for pre-charge conditioning.
Short Circuit Protection
The SC810 can tolerate a BAT pin short circuit to ground indefinitely. The current into a ground short is approximately 10mA.
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(c) 2008 Semtech Corporation
SC810
Applications Information (continued)
A short to ground on the IPRGM current programming pin will prevent startup. During charging, a short to ground applied to the IPRGM pin forces the SC810 into reset, turning off the output and holding it off until the short is removed. When the IPRGM short to ground is removed, the charger begins normal operation automatically without input power cycling.
VVIN=8.1V, VBAT=3.0V IBAT=700mA (Initially), PDISSIPATION=3.6W (Initially) IBAT (100mA/div)
VVIN (2V/div)
Over-Current Protection
Over-current protection is provided in all modes of operation, including CV regulation. The output current is limited to either the programmed pre-charge current limit value or the fast-charge current limit value, depending on the voltage at the output.
VBAT (2V/div)
VVIN ,VBAT=0V-- IBAT=0mA-- 1s/div
Figure 4 -- Thermal Limiting Example
Input Over-Voltage Protection
The VIN pin is protected from over-voltage to at least 30V above GND. When the input voltage exceeds the OverVoltage Protection (OVP) rising threshold ( VTOVP-R ), charging is halted. When the input voltage falls below the OVP falling threshold (VTOVP-F), charging resumes. An OVP fault turns off the STATB output. STATB is turned on again when charging restarts. The OVP threshold has been set relatively high to permit the use of poorly regulated adapters. Such adapters may output a high voltage until loaded by the charger. A too-low OVP threshold could prevent the charger from ever turning on and loading the adapter to a lower voltage. If the adapter voltage remains high despite the charging load, the fast thermal limiting feature will immediately reduce the charging current to prevent overheating of the SC810. This behavior is illustrated in Figure 4, in which VBAT = 3.0V, IFQ = 700mA, and VVIN is stepped from 0V to 8.1V. Initially, power dissipation in the SC820 is 3.6W. Notice the BAT output current is rapidly reduced to limit the internal die temperature, then continues to decline as the circuit board gradually heats up, further reducing the conduction of heat from the die to the ambient environment. The fast thermal limiting feature ensures compliance with CCSA YD/T 1591-2006, Telecommunication Industrial Standard of the People's Republic of China -- Technical Requirements and Test Method of Charger and Interface for Mobile Telecommunication Terminal, Section 4.2.3.1.
Operation Without a Battery
The SC810 can be operated as a 4.2V LDO regulator without the battery present, for example, factory testing. If this use is anticipated, the output capacitance C BAT should be at least 2.2F to ensure stability. To operate the charger without a battery, the ENB pin must be driven low or grounded.
Capacitor Selection
Low cost, low ESR ceramic capacitors such as the X5R and X7R dielectric material types are recommended. The BAT pin capacitor, CBAT, range is 1F to 22F. The VIN input capacitors, C VIN is typically between 0.1F and 2.2F, however a larger value will not degrade performance. Capacitance must be evaluated at the expected bias voltage, rather than the zero-volt capacitance rating.
PCB Layout Considerations
Layout for linear devices is not as critical as for a switching regulator. However, careful attention to detail will ensure reliable operation. Place input and output capacitors close to the device for optimal transient response and device behavior. Connect all ground connections directly to the ground plane. If there is no ground plane, connect to a common local ground point before connecting to board ground near the GND pin. Attaching the part to a larger copper
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(c) 2008 Semtech Corporation
SC810
Applications Information (continued)
footprint will enable better heat transfer from the device, especially on PCBs with internal ground and power planes. Note that the IPRGM pin resistor programs the fast-charge, pre-charge, and termination currents, so all will be modified by a change in the IPRGM pin resistor. An open-drain GPIO can be used directly to engage the parallel resistor RIPRGM_HI. Care must be taken to ensure that the RDS-ON of the GPIO is considered in the selection of RIPRGM_HI. Also important is the part-to-part and temperature variation of the GPIO RDS-ON, and their contribution to the High Current charge current tolerance. Note also that IPRGM will be pulled up briefly to as high as 3V during startup to check for an IPRGM static pinshort to ground. A small amount of current could, potentially, flow from IPRGM into the GPIO ESD structure through RIPRGM_HI during this event. While unlikely to do any harm, this effect must also be considered.
Dynamically Selectable Charge Current
The IPRGM resistance can be altered dynamically under processor control by switching a second IPRGM pin resistor. When the higher current is required, the switch is turned on, making the effective programming resistance equal to the parallel combination of the two resistors. The external circuit is illustrated in Figure 5.
IPRGM 4 RIPRGM_HI Hi/Lo Current Select RIPRGM
Figure 5. Dynamic selection of low and high charge currents.
(c) 2008 Semtech Corporation
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SC810
Outline Drawing -- MLPD-UT6 2x2
A
D
B
DIM
A A1 A2 b D D1 E E1 e L N aaa bbb
DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX
.020 .000 .024 .002 (.006) .007 .010 .012 .075 .079 .083 .061 .067 .071 .075 .079 .083 .026 .031 .035 .020 BSC .010 .014 .018 6 .003 .004 0.60 0.05 (0.152) 0.18 0.25 0.30 1.90 2.00 2.10 1.55 1.70 1.80 1.90 2.00 2.10 0.65 0.80 0.90 0.50 BSC 0.25 0.35 0.45 6 0.08 0.10 0.50 0.00
PIN 1 INDICATOR (LASER MARK)
E
A2 A aaa C C A1 D1 1 LxN E1 2 SEATING PLANE
N e
NOTES:
bxN bbb CAB
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.
(c) 2008 Semtech Corporation
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SC810
Land Pattern -- MLPD-UT6 2x2
H R
DIM
(C) K G Z
C G H K P R X Y Z
DIMENSIONS INCHES MILLIMETERS
(.077) .047 .067 .031 .020 .006 .012 .030 .106 (1.95) 1.20 1.70 0.80 0.50 0.15 0.30 0.75 2.70
Y
P X
NOTES: 1. 2. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE.
3.
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com
(c) 2008 Semtech Corporation
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