SLM6305

Part: SLM6305

Type: Li-ion Battery Charger / Synchronous Buck Converter

Description: A 2.5A Li-ion battery charger with wide voltage input (4.6–26V operating, 28V max), featuring a 550kHz fixed switching frequency, over 90% efficiency, and a preset 4.2V charging voltage with ±1% accuracy.

Operating Conditions:

• Supply voltage: 4.6–26 V
• Operating ambient temperature: -40 °C to 85 °C
• Switching frequency: 550 kHz (fixed)
• Regulated output voltage: 4.2 V

Absolute Maximum Ratings:

• Max input supply voltage (VIN): 28 V
• Max BAT voltage: 14 V
• Max junction temperature: 145 °C
• Max storage temperature: 125 °C

Key Specs:

• Max adjustable output current: 2.5 A
• Regulated output (float) voltage: 4.158 V to 4.242 V (Typ 4.2 V)
• Input supply current (shutdown mode): 20 μA (Typ)
• Trickle charge threshold voltage: 2.7 V to 3 V (Typ 2.85 V)
• Charge termination current threshold: 100 mA to 300 mA (Typ 200 mA) at RS = 33.3mΩ
• PMOSFET 'ON' resistance: 100 mΩ (Typ)
• NMOSFET 'ON' resistance: 100 mΩ (Typ)
• Recharge battery threshold voltage: 100 mV to 250 mV (Typ 150 mV)

Features:

• 28V high-voltage tolerant
• Automatic input current identification, adapter self-adaptive
• No reverse current protection diode required
• No external power MOS tube or freewheeling diode required
• Dual charge status indicators (NCHRG, NSTDBY)
• Soft start limits inrush current
• Battery temperature monitoring function
• Output short-circuit protection function
• Automatic recharge
• White LED driver capability

Applications:

• E-cigarettes
• Electric toys
• Power tools
• MP3, MP4 players
• Digital cameras
• Electronic dictionaries
• GPS
• Portable devices, various chargers

Package:

• DFN3x3-10L

Pin Description

VIN (Pin 1): Input voltage terminal. This terminal has a maximum withstand voltage of 28V, and the charging operating voltage is 4.6~26.0V.

VGC (Pin 2): Gate voltage clamp for the internal driver. Connect a 0.1μF capacitor between this terminal and VIN.

NCHRG (Pin 3): Charge status indicator. When the charger is charging the battery, this pin is pulled low by an internal switch, indicating that charging is in progress. Otherwise, this pin is in a high-impedance state.

NSTDBY (Pin 4): Charge complete indicator. When battery charging is complete, this pin is pulled low by an internal switch, indicating that charging is complete. Otherwise, this pin is in a high-impedance state.

NCE (Pin 5): Enable control terminal. A low input level enables the chip to operate normally; a high input level disables the chip from charging. The NCE pin can be driven by TTL or CMOS levels.

NTC (Pin 6): Battery temperature detection input terminal. Connect this pin to the output of the battery's NTC sensor. If the voltage on the NTC pin is less than 180mV or greater than 1.35V, it means the battery temperature is too high or too low, and charging is paused. If NTC is left floating, the battery temperature detection function is canceled, and other charging functions operate normally.

BAT (Pin 7): Battery voltage detection terminal. When charging stops, the leakage current at the BAT pin is less than 3μA.

VS (Pin 8): Battery current detection terminal. A high-precision milliohm resistor RS is connected between this terminal and BAT, used to set the fast charging current. The formula is: I_BAT = 0.0667 / R_S (A).

GND (Pin 9): Power ground. The GND terminal must be reliably connected to the chip's bottom thermal pad and the PCB copper pour.

LX (Pin 10): Internal power MOSFET connection point. LX is the current output terminal of the SLM6305 and is connected to an external inductor as the input terminal for the battery charging current.

DC Electrical Characteristics (Unless otherwise specified, VIN = 5V ±2%, NCE connected to GND, TA = 25 °C)

Symbol	Parameter	Condition	Min	Typ	Max	Unit
VIN	Input Supply Voltage		4.6	5	26	V
VUV	VIN Undervoltage Lockout Threshold	VIN high to low	3.8	3.95	4.1	V
VUVHYS	VIN Undervoltage Lockout Hysteresis			300		mV
IIN	Input Supply Current	Standby mode (charge termination)		130	260	μA
IIN	Input Supply Current	Shutdown mode (NCE high)		20	40	μA
VFLOAT	Regulated Output (Float) Voltage		4.158	4.2	4.242	V
IBAT	BAT Pin Current: (Current mode test condition is VBAT =3.8V)	RS =33.3mΩ, current mode	1.8	2	2.2	A
IBAT	BAT Pin Current: (Current mode test condition is VBAT =3.8V)	Standby mode, VBAT =4.2V		2.3	4.6	μA
IBAT	BAT Pin Current: (Current mode test condition is VBAT =3.8V)	Stop mode (VIN <VBAT or VIN <VUV)		2.6	5.2	μA
IBAT	BAT Pin Current: (Current mode test condition is VBAT =3.8V)	Shutdown mode (NCE high)		0		μA
ITRIKL	Trickle Charge Current	VBAT <VTRIKL, RS =33.3mΩ, current mode		200		mA
VTRIKL	Trickle Charge Threshold Voltage	VBAT rising	2.7	2.85	3	V
VTRHYS	Trickle Charge Hysteresis Voltage			100		mV
VBLV	Battery Terminal Short-Circuit Protection Threshold Voltage			2.2		V
VINSL	Input Voltage Drop Protection			4.55		V
VASD	VIN -VBAT Lockout Threshold Voltage	VIN low to high	150	200	300	mV

		VIN high to low	10	80	130	mV
ITERM	Charge Termination Current Threshold	RS =33.3mΩ	100	200	300	mA
VNCHRG	NCHRG Pin Output Low Voltage	INCHRG =5mA		0.5		V
VNSTDBY	NSTDBY Pin Output Low Voltage	INSTDBY =5mA		0.5		V
VNCE_L	NCE Pin Low Level (Enable)				0.8	V
VNCE_H	NCE Pin High Level (Disable)		2.5			V
INTC	NTC Pin Current		45	50	55	μA
VNTC_H	NTC Pin High-End Trip Voltage			1.35		V
VNTCH_HYS	NTC Pin High-End Trip Voltage Hysteresis			50		mV
VNTC_L	NTC Pin Low-End Trip Voltage			180		mV
VNTCL_HYS	NTC Pin Low-End Trip Voltage Hysteresis			40		mV
ΔVRECHRG	Recharge Battery Threshold Voltage		100	150	250	mV
FREQ	Oscillation Frequency		450	550	650	kHz
RPFET	PMOSFET 'ON' Resistance			100		mΩ
RNFET	NMOSFET 'ON' Resistance			100		mΩ
TLIM	Junction Temperature in Limited Temperature Mode			145		°C
tSS	Soft Start Time		300			us
tRECHRG	Recharge Comparator Filter Time	VBAT high to low		1		ms
tTERM	Termination Comparator Filter Time	IBAT drops below ITERM		1		ms

• Input Supply Voltage (VIN): -0.3V~28V

• VGC: VIN-7V~VIN+0.3V

• NCHRG, NSTDBY: -0.3V~28V

• BAT: -0.3V~14V

• VS: -0.3V~14V

• LX: -0.3V~28V

• Others: -0.3V~7V

• BAT Short-Circuit Duration: Continuous

• Maximum Junction Temperature: 145 °C

• Operating Ambient Temperature Range: -40 °C ~85 °C

• Storage Temperature Range: -65 °C ~125 °C

• Soldering Temperature (10 seconds): 260 °C

• Operating voltage up to 26.0V

• 550kHz fixed switching frequency

• Output efficiency over 90%

• Maximum 2.5A adjustable output current

• Automatic input current identification, adapter self-adaptive

• No reverse current protection diode required

• No external power MOS tube or freewheeling diode required

• 4.2V charging voltage with ±1% accuracy

• 28V high-voltage tolerant dual charge status indicators

• Shutdown current only 20μA

• 2.9V trickle charge

• Soft start limits inrush current

• Battery temperature monitoring function

• Output short-circuit protection function

• Miniaturized DFN3x3-10L package

Features

• E-cigarettes
• Electric toys
• Power tools
• MP3, MP4 players
• Digital cameras
• Electronic dictionaries
• GPS
• Portable devices, various chargers

Applications

The DFN3x3-10L package has a small form factor. For chip heat dissipation, special attention must be paid to the PCB layout. This can maximize the usable charging current, which is very important. The thermal path for dissipating heat generated by the IC goes from the chip to the lead frame and then through the bottom thermal pad to the PCB copper plane. The PCB copper foil acts as the primary heat sink for the IC, and its area should be as wide as possible, extending outwards to a larger copper area to dissipate heat into the surrounding environment.

Placing vias on the PCB to internal layers or the back layer also significantly improves the overall thermal performance of the charger, as shown in Figure 3. At the SLM6305 position on the PCB, a 1.7*3.0mm square PAD should be placed as a heat sink, and several 0.8mm diameter vias should be placed on the PAD as thermal vias. When soldering the chip, solder should be filled from the back layer of the PC board to ensure effective connection between the SLM6305's built-in thermal pad and the PC board's thermal pad, thereby ensuring efficient heat dissipation for the SLM6305. Efficient chip heat dissipation is a prerequisite for the chip to maintain a large charging current for a long time.

Figure 5 PCB Layout

When designing the PCB layout, other heat sources on the board unrelated to the charging IC also need to be considered, as their own temperature will affect the overall temperature rise and maximum charging current.

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Application Notes