MIC4801 - LED driver Microchip - Free user manual and instructions

Product Type	LED Driver Module
Brand	Microchip
Model	MIC4801
Input Voltage Range	4.5V to 60V DC
Output Current	Up to 1A (adjustable)
Output Voltage	Adjustable, up to 60V (buck topology)
Efficiency	Up to 95%
Switching Frequency	Up to 1 MHz
Dimming Method	PWM (external signal)
Protection Features	Overcurrent, overvoltage, thermal shutdown
Operating Temperature	-40°C to +125°C
Mounting Type	Surface Mount (SMD)
Package Type	QFN-16 (typical)
Weight	Approx. 0.5 g
Dimensions	4 mm x 4 mm x 0.8 mm (typical)
Maintenance	No user maintenance required; keep clean and dry
Safety	Operate within rated voltage; ensure proper heat dissipation
Replaceable Parts	None; integrated circuit
General Information	High-efficiency, step-down LED driver with integrated MOSFET

Frequently Asked Questions - MIC4801 Microchip

What is the input voltage range of the MIC4801?

The input voltage range is from 4.5V to 60V DC.

How much output current can the MIC4801 provide?

It can provide up to 1A of output current, adjustable via external resistor.

Can I dim the LEDs with this driver?

Yes, the MIC4801 supports PWM dimming by applying a PWM signal to the dimming pin.

What is the typical efficiency of the MIC4801?

Typical efficiency is up to 95% under optimal conditions.

What protections does the MIC4801 have?

It includes overcurrent, overvoltage, and thermal shutdown protection.

What is the operating temperature range?

The device operates from -40°C to +125°C.

Do I need an external MOSFET?

No, the MIC4801 has an integrated power MOSFET.

What is the switching frequency?

The switching frequency can be set up to 1 MHz via an external resistor.

Can the output voltage be higher than the input?

No, the MIC4801 is a buck (step-down) converter, so output voltage must be lower than input.

How do I set the output current?

The output current is set by an external sense resistor connected to the output.

USER MANUAL MIC4801 Microchip

High Efficiency 600mA Single Channel Linear WLED Driver with Ultra Fast PWM™ Control

General Description

The MIC4801 is a high efficiency White LED (WLED) driver designed to drive a single LED up to 600mA. The MIC4801 constant current driver is designed to drive high power LED's in various lighting applications. The MIC4801 provides the highest possible efficiency as this architecture has no switching losses present in traditional charge pumps or inductive boost circuits. It features a typical dropout of 130mV at 400mA. This allows the LEDs to be driven directly from the voltage source eliminating switching noise/losses present with the use of boost circuitry. The high accuracy ( ± 1% typical) current regulated WLED channel ensures uniform display illumination under all conditions. The brightness is controlled through an Ultra Fast PWM ^™ Control interface operating down to less than 1% duty cycle.

The MIC4801 is available in an 8-pin SOIC package with a junction temperature range of -40°C to +125°C.

Datasheets and support documentation can be found on Micrel's web site at: www.micrel.com.

Features

• High Efficiency (no Voltage Boost losses)
- Ultra Fast PWM™ control (200Hz to 500kHz)
- Input voltage range: 3.0V to 5.5V
- Dropout of 130mV at 400mA
• Programmable LED current with external resistor
• Current accuracy of ±1% typical

Applications

• Bill board displays
• Marquee displays
• Instrument displays
• Architectural lighting

Typical Application

High Current Lighting Schematic

Ultra Fast PWM is a trademark of Micrel, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax [phone] • http://www.micrel.com

Ordering Information

Part Number Temperature Range Package
MIC4801YM -40°C to +125°C 8-Pin SOIC

Pin Configuration

8-Pin SOIC (M) (Top View)

Pin Description

Pin Number	Pin Name	Pin Function
1 VIN Voltage Input. Connect at least 2.2μF ceramic capacitor between VIN and GND.
2	EN	Enable LED drivers. This pin can be used as a PWM input for dimming of WLEDs. Do not leave floating.
3	RSET	An internal 1.27V reference sets the nominal maximum WLED current. Example, apply a 12.1kΩ resistor between RSET and GND to set LED current to 416mA at 100% duty cycle.
4	GND	Ground.
5	D1	LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED.
6	D1	LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED.
7	D1	LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED.
8	D1	LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED.

Absolute Maximum Ratings ⁽¹⁾

Main Input Voltage ( V_IN ) -0.3V to +6V

Enable Input Voltage ( V_EN )....-0.3V to +6V

LED Driver Voltage ( V_D1 ) -0.3V to +6V

Power Dissipation ....Internally Limited

Lead Temperature (soldering, 10sec.)....260°C

Storage Temperature ( T_s ) -65°C to +150°C

Operating Ratings ⁽²⁾

Supply Voltage ( V_IN )....+3.0V to +5.5V

Enable Input Voltage ( V_EN ) 0V to V_IN

LED Driver Voltage ( V_D1 ) 0V to V_IN

Junction Temperature ( T_J ) -40°C to +125°C

Junction Thermal Resistance

SOIC-8L JA09....98.9°C/W

Electrical Characteristics

V_IN = V_EN = 5V, R_SET = 12.1kΩ; V_D1 = 1.2V; T_J = 25° C, bold values indicate -40° C ≤ T_J ≤ 125° C; unless noted.

Parameter	Conditions	Min			Typ
Current\ Accuracy(3)		374	416	458 mA
Drop-out	Where ILED = 90% of LED current seen at VDROP NOM = 1.2V, 100% brightness level		130	250	mV
Ground/Supply Bias Current	IOUT = 416mA		2.2	2.9	mA
Shutdown Current	VEN = 0V		0.01	1	μA
PWM Dimming
Enable Input Voltage ( VEN )	Logic Low			0.2	V
	Logic High	1.2			V
Enable Input Current	VIH ≥ 1.2V		0.01	1	μA
Current Source Delay (50% levels)	Shutdown to on Standby to on On to Standby		4020.3	60	μsμsμs
Current Source Transient Time (10%-90%)	TRISE TFALL		10.3		μsμs
Stand-by to Shutdown Time	VEN = 0V	10	20	40	ms

Notes:

1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. As determined by average current based on R_SET resistance.

Typical Characteristics

Functional Characteristics

Functional Diagram

Functional Description

The MIC4801 is a single channel linear LED driver with a maximum 600mA current capability. The LED driver is designed to maintain proper current regulation with LED current accuracy of ±10%. The dropout is 130mV at 400mA. The low dropout of the linear drivers allows the LEDs to be driven directly from the battery voltage and eliminates the need for boost or large and inefficient charge pumps. The maximum LED current for each channel is set via an external resistor. Dimming is controlled by applying a PWM signal to the EN pin. The MIC4801 accommodates a wide PWM frequency range as outlined in the application information section.

Block Diagram

As shown in Figure 1, the MIC4801 consists of current mirrors set to copy a master current determined by R_SET . The linear LED drivers have a designated control block for enabling and dimming of the LEDs. The MIC4801 dimming is controlled by the Ultra Fast PWM™ control block that receives PWM signals for dimming.

VIN

The input supply ( V_IN ) provides power to the linear LED drivers and the control circuitry. The V_IN operating range is 3V to 5.5V. A minimum bypass capacitor of 2.2 µ F should be placed close to the input (VIN) pin and the ground (GND) pin. Refer to the layout recommendations section for details on placing the input capacitor (C1).

EN

The EN pin is equivalent to the enable pin for the linear drivers on the MIC4801. It can also be used for dimming by applying a PWM signal. See the PWM Dimming Interface in the Application Information section for details. Pulling the EN low for more than 40ms puts the MIC4801 into a low I_Q sleep mode. The EN pin cannot be left floating; a floating enable pin may cause an indeterminate state on the outputs. The first pulse on the EN pin must be equal or greater than 60μs to wake the part up in a known state. This equates to a 8.3kHz PWM signal at equal or greater than 50% duty cycle. Higher PWM frequencies may be used but the first pulse must be equal or greater than 60μs.

RSET

The R_SET pin is used to set the peak current of the linear driver by connecting a R_SET resistor to ground. The theoretical average LED current can be estimated by equation (1):

I _ LED (mA) = 4 9 2 0* D / R _ SET (kΩ) 1

R _ SET (kΩ) = 4 9 2 0* D / I _ LED (mA) 2

D is the duty cycle of the LED current during PWM dimming. When the device is fully ON the duty cycle equals 100% (D = 1). A plot of I_LED versus R_SET is shown in Figure 2.

Due to DC losses across current paths internal and external to the package, the calculated R_SET resistance equation is modified by a factor K, where K is calculated to be 0.140kΩ.

R _ SET (kΩ) = 4 9 2 0* D / I _ LED (mA) + 0. 1 4 0 (kΩ) 3

I _ LED (mA) = 4 9 2 0* D / ((R _ SET (kΩ) - 0. 1 4 0 (kΩ)) 4

The modified LED current equation is more accurate in determining the actual LED current based on the RSET resistor value.

Figure 2. Peak LED Current vs. R_SET

D1

The D1 pins are the linear driver inputs for the LED. Connect the anode of the LED to VIN and the cathode to the D1 pins. All the D1 pins must be connected together. The D1 voltage at dropout is the minimum voltage required by the linear driver in order for the LED to be fully biased.

GND

The ground pin is the ground path for the linear driver. The ground of the input capacitor should be routed with low impedance traces to the GND pin and made as short as possible. Refer to the layout recommendations for more details.

Application Information

Ultra Fast PWM™ Dimming Interface

The MIC4801 supports a wide range of PWM control signal frequencies from 200Hz to 500kHz. This extremely wide range of control provides ultimate flexibility for handheld applications using high frequency PWM control signals.

WLED dimming is achieved by applying a pulse width modulated (PWM) signal to the EN pin. For PWM frequencies between 200Hz – 10kHz the MIC4801 supports a duty cycle range from 1% to 100%, as shown in Figure 3. The MIC4801 incorporates an internal shutdown delay to ensure that the internal control circuitry remains active during PWM dimming. This feature prevents the possibility of backlight flickering when using low frequency PWM control signals. The MIC4801 also supports Ultra Fast PWM ^™ frequencies from 20kHz to 500kHz. Due to input signal propagation delay, PWM frequencies above 20kHz have a non-linear relationship between the duty cycle and the average LED current, as shown in Figure 3 and 4. Figures 6 through 9 show the WLED current response when a PWM signal is applied to the EN pin ⁽¹⁾ .

(1) From the low I_Q sleep mode higher PWM frequencies require a logic high enable signal for 60 µ s to first enable the MIC4801 prior to PWM dimming.

Figure 3. Average Current per LED Dimming by Changing PWM Duty Cycle for PWM Frequencies up to 20kHz

Figure 4. Channel Current Response to PWM Control Signal Frequencies from 50kHz to 500kHz

Figure 5. Minimum Duty Cycle for Varying PWM Frequency

Figure 6. PWM Signal at 1% Duty Cycle ( I_avg = 6mA )

Figure 7. PWM Signal at 20% Duty Cycle ( I_avg = 120mA )

Figure 8. PWM Signal at 50% Duty Cycle ( I_avg = 300mA )

Figure 9. PWM Signal at 80% Duty Cycle ( I_avg = 480mA )

Thermal Consideration

The MIC4801 thermal considerations involve calculating the junction temperature based on the voltage drop across the package and the LED current. The voltage drop across the package is equal to the voltage at D1 with respect to ground times the LED current.

P _ LOSS = I _ LED * V _ D 1

The temperature rise (ΔT) is calculated:

ΔT = P _ LOSS * θ_ JA

Assuming the I_LED is 600mA and V_D1 is 500mV at 20°C room temperature, we can calculate the junction temperature:

T _ J = T _ A + ΔT

T _ J = 2 0 ^ ° C + 0. 3 W * 9 8. 9 ^ ° C / W

T _ J = 2 0 ^ ° C + 2 9. 7 ^ ° C = 4 9. 7 ^ ° C

The junction temperature will be around 49.7°C.

MIC4801 Typical Application Circuit

Bill of Materials

Item	Part Number	Manufacturer	Description
C1	C1608X5R0J225K	TDK(1)	Ceramic Capacitor, 2.2μF, 6.3V, X5R, Size 0603	1
	06036D225KAT2A	AVX(2)
	GRM188R60J225KE19D	Murata(3)
	VJ0603G225KXYAT	Vishay(4)
LED	R42180	Seoul Semi(5)	Low High Power WLED 1
R1	CRCW060312K1FKEA	Vishay(4) Resistor, 1%, 1/16W, Size 0603 1
U1	MIC4801YM	Micrel, (6)	600mA Single Channel Ultra Fast PWM TM Inc. Linear WLED Driver	1

Notes:

1. TDK: www.tdk.com
2. AVX: www.avx.com
3. Murata: www.murata.com
4. Vishay: www.vishay.com
5. Seoul Semi: http://www.acriche.com/en
6. Micrel, Inc.: www.micrel.com

Qty.

Layout Recommendations

Top Layer

Bottom Layer

Package Information

TOP VIEW

BOTTOM VIEW

END VIEW

DETAIL "A"
8-Pin SOIC (M)

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