MCP1662 High-Voltage Step-Up LED Driver with UVLO and Open Load Protection Data Sheet

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 2014-2015 Microchip Technology Inc.

DS20005316E-page 1

MCP1662

Features

• 36V,  800 m

 Integrated Switch

• Up to 92% Efficiency

• Drive LED Strings in Constant Current

• 1.3A Peak Input Current Limit:

- I

LED

 up to 200 mA @ 5.0V V

IN

, 4 White LEDs

- I

LED 

up to 125 mA @ 3.3V V

IN

, 4 White LEDs

- I

LED

 up to 100 mA @ 4.2V V

IN

, 8 White LEDs

• Input Voltage Range: 2.4V to 5.5V

• Feedback Voltage Reference: V

FB

= 300 mV

• Undervoltage Lockout (UVLO):

- UVLO @ V

IN

 Rising: 2.3V, typical

- UVLO @ V

IN

 Falling: 1.85V, typical

• Sleep Mode with 20 nA Typical Quiescent Current

• PWM Operation: 500 kHz Switching Frequency

• Cycle-by-Cycle Current Limiting

• Internal Compensation

• Open Load Protection (OLP) in the Event of:

- Feedback pin shorted to GND (prevent 

excessive current into LEDs)

- Disconnected LED string (prevent overvoltage 

to the converter’s Output and SW pin)

• Overtemperature Protection

• Available Packages:

- 5-Lead SOT-23

- 8-Lead 2x3 TDFN

Applications

• Two and Three-Cell Alkaline or NiMH/NiCd White 

LED Driver for Backlighting Products

• Li-Ion Battery LED Lighting Application

• Camera Flash

• LED Flashlights and Backlight Current Source

• Medical Equipment

• Portable Devices:

- Handheld Gaming Devices

- GPS Navigation Systems

- LCD  Monitors

- Portable DVD Players

General Description

The MCP1662 device is a compact, space-efficient,
fixed-frequency, non-synchronous step-up converter
optimized to drive LED strings with constant current
from a two- or three-cell alkaline or lithium Energizer

®

,

or NiMH/NiCd, or one-cell Lithium-Ion or Li-Polymer
batteries.

The device integrates a 36V, 800 m

 low-side switch,

which is protected by the 1.3A cycle-by-cycle inductor
peak current limit operation. All compensation and pro-
tection circuitry is integrated to minimize the number of
external components.

The internal feedback (V

FB

) voltage is set to 300 mV for

low power dissipation when sensing and regulating the
LED current. A single resistor sets the LED current.

The device features an Undervoltage Lockout (UVLO)
that avoids start-up with low inputs or discharged bat-
teries for two-cell-powered applications.

There is an open load protection (OLP) which turns off
the operation in situations when the LED string is acci-
dentally disconnected or the feedback pin is short-cir-
cuited to GND.

For standby applications (EN = GND), the device stops
switching, enters into Sleep mode and consumes
20 nA typical of input current.

Package Types

* Includes Exposed Thermal Pad (EP); see

Table 3-1

MCP1662 

SOT-23

MCP1662 
2x3 TDFN*

V

FB

GND

EN

1

2

3

5

4

V

IN

SW

SW

S

GND

NC

P

GND

NC

1

2

3

4

8

7

6

5

V

IN

EN

V

FB

EP

9

High-Voltage Step-Up LED Driver with UVLO and Open Load Protection

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MCP1662

DS20005316E-page 2

 2014-2015 Microchip Technology Inc.

Typical Application

V

IN

GND

V

FB

C

OUT

10 µF

C

IN

4.7 – 30 µF

L

4.7 – 10 µH

SW

EN

+

-

ALKAL

INE

ON

OFF

MCP1662

+

-

ALAKL

INE

V

IN

2.4V – 3.0V

LED6 

12

R

SET

LED1 

I

LED

= 25 mA

I

LED

=

0.3V

R

SET

LED2 

V

FB

= 0.3V

Maximum LED Current in Regulation vs. Input Voltage, T

A

= + 25°C

 

V

OUT

0

50

100

150

200

250

2

2.5

3

3.5

4

4.5

5

5.5

I

OUT

(mA)

V

IN

(V)

4

wLEDs

, L = 4.7 µH

8 wLEDs, L = 10 µH

L

= 4.7 µH for maximum 4 white LEDs

L

= 10 µH for 5 to 10 white LEDs

C

IN

= 4.7-10 µF for V

IN

> 2.5V

C

IN

= 20-30 µF for V

IN

< 2.5V

D
MBR0540

I

LED

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 2014-2015 Microchip Technology Inc.

DS20005316E-page 3

MCP1662

1.0

ELECTRICAL 
CHARACTERISTICS

Absolute Maximum Ratings †

V

SW

– GND .....................................................................+36V

EN, V

IN

– GND ...............................................................+6.0V

V

FB

...............................................................................+0.35V

Power Dissipation  ....................................... Internally Limited
Storage Temperature .................................... -65

°

C to +150

°

C

Ambient Temperature with Power Applied .... -40

°

C to +125

°

C

Operating Junction Temperature................... -40

°

C to +150

°

C

ESD Protection on All Pins:

HBM ................................................................. 4 kV
MM ..................................................................300V

† Notice: Stresses above those listed under “Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of
the device at those or any other conditions above those
indicated in the operational sections of this specifica-
tion is not intended. Exposure to maximum rating con-
ditions for extended periods may affect device
reliability.

DC AND AC CHARACTERISTICS

Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature 
T

A

= +25°C,  V

IN

= 3.3V, V

OUT

= 9V or 3 white LEDs (V

F

= 2.75V @ I

F

= 20 mA  or  V

F

= 3.1V  @  I

F

= 100 mA), 

I

LED

= 20 mA,  C

IN

= C

OUT

= 10 µF,  X7R  ceramic,  L = 4.7 µH.

Boldface specifications apply over the controlled T

A

 range of -40°C to +125°C.

Parameters

Sym.

Min.

Typ.

Max.

Units

Conditions

Input Voltage Range

V

IN

2.4

5.5

V

Note 1

Undervoltage Lockout (UVLO)

UVLO

START

2.3

V

V

IN

 rising, I

LED

= 20 mA

UVLO

STOP

1.85

V

V

IN

 falling, I

LED

= 20 mA

Maximum Output Voltage

V

OUTmax

32

V

Maximum Output Current

I

OUT

100

mA

4.2V  V

IN

, 8 LEDs

125

mA

3.3V V

IN

, 4 LEDs

200

mA

5.0V V

IN

, 4 LEDs

Feedback Voltage Reference

V

FB

275

300

325

mV

Feedback Open Load
Protection (OLP) Threshold

V

FB_OLP

50

mV

V

FB

 falling (

Note 2

)

Feedback Input Bias Current

I

VFB

0.005

µA

Shutdown Quiescent Current

I

QSHDN

0.02

µA

EN = GND

NMOS Peak Switch Current 
Limit

I

N(MAX)

1.3

A

Note 2

NMOS Switch Leakage

I

NLK

0.4

µA

V

IN

= V

SW

= 5V;

V

OUT

=   5.5V 

V

EN

= V

FB

= GND

NMOS Switch ON Resistance

R

DS(ON)

0.8

V

IN

= 5V,

I

LED

= 100 mA,

4 series white LEDs
(

Note 2

)

Feedback Voltage
Line Regulation

|(

V

FB

/V

FB

)/

V

IN

|

0.25

%/V

V

IN

= 3.0V to 5V

Maximum Duty Cycle

DC

MAX

90

%

Note 2

Switching Frequency

f

SW

425

500

575

kHz

±15%

EN Input Logic High

V

IH

85

% of V

IN

Note 1:

Minimum input voltage in the range of V

IN

 (V

IN

< 5.5V < V

OUT

) depends on the maximum duty cycle 

(DC

MAX

) and on the output voltage (V

OUT

), according to the boost converter equation:

V

INmin

= V

OUT

x (1 – DC

MAX

). Output voltage is equal to the LED voltage plus the voltage on the sense 

resistor (V

OUT

 = V

LED

+ V_R

SET

).

2:

Determined by characterization, not production tested.

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MCP1662

DS20005316E-page 4

 2014-2015 Microchip Technology Inc.

EN Input Logic Low

V

IL

7.5

%  of  V

IN

EN Input Leakage Current

I

ENLK

0.025

µA

V

EN

= 5V

Start-up Time

t

SS

100

µs

EN Low-to-High,
90% of I

LED

(

Note 2

Figure 2-10

)

Thermal Shutdown
Die Temperature

T

SD

150

°C

Die Temperature Hysteresis

T

SDHYS

15

°C

TEMPERATURE SPECIFICATIONS

Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature 
T

A

= +25°C,  V

IN

= 3.0V, I

OUT

= 20 mA,  V

OUT

= 12V,  C

IN

= C

OUT

= 10 µF, X7R ceramic, L = 4.7 µH.

Boldface specifications apply over the air-forced T

A

 range of -40°C to +125°C.

Parameters

Sym.

Min.

Typ.

Max.

Units

Conditions

Temperature Ranges

Operating Junction Temperature 
Range

T

J

-40

+125

°C

Steady State

Storage Temperature Range

T

A

-65

+150

°C

Maximum Junction Temperature

T

J

+150

°C

Transient

Package Thermal Resistances

Thermal Resistance, 5L-SOT-23

JA

201.0

°C/W

Thermal Resistance, 8L 2x3 TDFN

JA

52.5

°C/W

DC AND AC CHARACTERISTICS (CONTINUED)

Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature 
T

A

= +25°C,  V

IN

= 3.3V, V

OUT

= 9V or 3 white LEDs (V

F

= 2.75V @ I

F

= 20 mA  or  V

F

= 3.1V  @  I

F

= 100 mA), 

I

LED

= 20 mA,  C

IN

= C

OUT

= 10 µF,  X7R  ceramic,  L = 4.7 µH.

Boldface specifications apply over the controlled T

A

 range of -40°C to +125°C.

Parameters

Sym.

Min.

Typ.

Max.

Units

Conditions

Note 1:

Minimum input voltage in the range of V

IN

 (V

IN

< 5.5V < V

OUT

) depends on the maximum duty cycle 

(DC

MAX

) and on the output voltage (V

OUT

), according to the boost converter equation:

V

INmin

= V

OUT

x (1 – DC

MAX

). Output voltage is equal to the LED voltage plus the voltage on the sense 

resistor (V

OUT

 = V

LED

+ V_R

SET

).

2:

Determined by characterization, not production tested.

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DS20005316E-page 5

MCP1662

2.0

TYPICAL PERFORMANCE CURVES

Note: Unless otherwise indicated: V

IN

= 3.3V,  I

LED

= 20 mA,  V

OUT

= 12V or 4 white LEDs (V

F

= 2.75V  @  I

F

= 20 mA  or

V

F

= 3.1V  @  I

F

= 100 mA), C

IN

= C

OUT

= 10 µF, X7R ceramic, L = 4.7 µH.

FIGURE 2-1:

4 White LEDs, I

LED

 vs. V

IN

.

FIGURE 2-2:

4 White LEDs, I

LED

 vs. 

Ambient Temperature.

FIGURE 2-3:

8 White LEDs, I

LED

 vs. 

Ambient Temperature.

FIGURE 2-4:

4 White LEDs, Efficiency vs. 

I

LED

.

FIGURE 2-5:

8 White LEDs, Efficiency vs. 

I

LED

.

FIGURE 2-6:

Maximum I

LED

 vs. V

IN

.

Note:

The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.

0

25

50

75

100

125

150

2.3

2.7

3.1

3.5

3.9

4.3

4.7

5.1

5.5

LED Current (mA)

Input Voltage (V)

R

SET

= 15

ȍ

 

R

SET

= 6.2

ȍ

 

R

SET

= 2.2

ȍ

 

R

SET

= 3.2

ȍ

 

4 x wLED, L = 4.7 µH

0

20

40

60

80

100

120

-40 -25 -10

5

20

35

50

65

80

95 110 125

LED Current (mA)

Ambient Temperature (

o

C)

R

SET

= 15

ȍ

 

4 x wLED, L = 4.7 µH, V

IN 

= 3.3V

R

SET

= 6.2

ȍ

 

R

SET

= 3.2

ȍ

 

0

20

40

60

80

100

120

-40 -25 -10

5

20

35

50

65

80

95 110 125

LED Current (mA)

Ambient Temperature (

o

C)

R

SET

= 15

ȍ

 

8 x wLED, L = 10 µH, V

IN 

= 4.2V

R

SET

= 6.2

ȍ

 

R

SET

= 3.2

ȍ

 

0

10

20

30

40

50

60

70

80

90

100

0

25

50

75 100 125 150 175 200 225 250

Efficiency

 (%

)

I

LED

(mA)

V

IN

= 3.0V

V

IN

= 4.0V

V

IN

= 5.5V

L = 4.7 µH,
4 wLEDs

0

10

20

30

40

50

60

70

80

90

100

0

20

40

60

80

100

120

140

160

Efficiency

 (%

)

I

LED

(mA)

V

IN

= 4.0V

V

IN

= 5.5V

V

IN

= 3.0V

L = 10 µH,
8 wLEDs

0

50

100

150

200

250

300

2.3

2.7

3.1

3.5

3.9

4.3

4.7

5.1

5.5

LED Current (mA)

Input Voltage (V)

8 wLEDs, L = 10 µH

4 wLEDs, L = 4.7 µH

5 wLEDs, L = 10 µH

2 wLEDs, L = 4.7 µH

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MCP1662

DS20005316E-page 6

 2014-2015 Microchip Technology Inc.

Note: Unless otherwise indicated: V

IN

= 3.3V,  I

LED

= 20 mA,  V

OUT

= 12V or 4 white LEDs (V

F

= 2.75V  @  I

F

= 20 mA  or

V

F

= 3.1V  @  I

F

= 100 mA), C

IN

= C

OUT

= 10 µF, X7R ceramic, L = 4.7 µH.

FIGURE 2-7:

Undervoltage Lockout 

(UVLO) vs. Ambient Temperature.

FIGURE 2-8:

Shutdown Quiescent 

Current,

 

I

QSHDN

, vs. V

IN

 (EN = GND).

FIGURE 2-9:

Switching Frequency, f

SW

 

vs. Ambient Temperature.

FIGURE 2-10:

Soft Start Time vs. Number 

of LEDs.

FIGURE 2-11:

Start-Up When 

V

IN

= V

ENABLE

.

FIGURE 2-12:

Start-Up After Enable.

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

2.3

2.4

2.5

-40 -25 -10

5

20

35

50

65

80

95 110 125

UVLO Thresholds  (V) 

Ambient Temperature (

o

C) 

UVLO Stop 

 

 
 

UVLO Start 

 

 
 

0

10

20

30

40

50

2.2 2.5 2.8 3.1 3.4 3.7 4.0 4.3 4.6 4.9 5.2 5.5

Shutdow

n Iq 

(nA)

Input Voltage (V)

450

475

500

525

550

-40 -25 -10

5

20

35

50

65

80

95 110 125

Sw

itching Frequency

 (kHz)

Ambient Temperature (°C)

0

50

100

150

200

250

3

4

5

6

7

8

Start-up T

ime 

(µs)

Number of LEDs

Blue Bars - I

LED

= 20 mA

Red Bars - I

LED 

= 40  mA

I

LED

10 mA/div

V

EN

2V/div

V

IN

2V/div

3 LEDs, I

LED

= 20 mA

40 µs/div

I

LED

10 mA/div

V

EN

2V/div

V

IN

2V/div

3 LED, I

LED

= 20 mA

40 µs/div

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 2014-2015 Microchip Technology Inc.

DS20005316E-page 7

MCP1662

Note: Unless otherwise indicated: V

IN

= 3.3V,  I

LED

= 20 mA,  V

OUT

= 12V or 4 white LEDs (V

F

= 2.75V  @  I

F

= 20 mA  or

V

F

= 3.1V  @  I

F

= 100 mA), C

IN

= C

OUT

= 10 µF, X7R ceramic, L = 4.7 µH.

FIGURE 2-13:

100 Hz PWM Dimming, 15% 

Duty Cycle.

FIGURE 2-14:

100 Hz PWM Dimming, 85% 

Duty Cycle.

FIGURE 2-15:

Open Load (LED Fail or FB 

to GND) Response.

FIGURE 2-16:

3.3V Input, 20 mA 3 White 

LEDs PWM Discontinuous Mode Waveforms.

FIGURE 2-17:

3.3V Input, 100 mA 3 White 

LEDs PWM Continuous Mode Waveforms.

I

LED

10 mA/div

V

SW

4V/div

V

EN

3V/div

2 ms/div

3 LEDs

I

LED

100 mA/div

V

SW

4V/div

V

EN

3V/div

2 ms/div

V

FB

300 mV/div

I

LED

10 mA/div

V

SW

4V/div

50 ms/div

V

OUT

3V/div

I

LED

20 mA/div

V

SW

4V/div

1 µs/div

3 LEDs

V

OUT

3V/div

I

LED

50 mA/div

V

SW

4V/div

1 µs/div

3 LEDs

3 LEDs

3 LEDs

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MCP1662

DS20005316E-page 8

 2014-2015 Microchip Technology Inc.

3.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in 

Table 3-1

.

3.1

Feedback Voltage Pin (V

FB

)

The V

FB

 pin is used to regulate the voltage across the

R

SET

 sense resistor to 300 mV to keep the output LED

current in regulation. Connect the cathode of the LED
to the V

FB

 pin.

3.2

Signal Ground Pin (S

GND

)

The signal ground pin is used as a return for the inte-
grated reference voltage and error amplifier. The signal
ground and power ground must be connected exter-
nally in one point.

3.3

Switch Node Pin (SW)

Connect the inductor from the input voltage to the SW
pin. The SW pin carries inductor current and has a typ-
ical value of 1.3A peak. The integrated N-Channel
switch drain is internally connected to the SW node.

3.4

Not Connected (NC)

This is an unconnected pin.

3.5

Power Supply Input Voltage Pin 
(V

IN

)

Connect the input voltage source to V

IN

. The input

source should be decoupled from GND with a 4.7 µF
minimum capacitor.

3.6

Power Ground Pin (P

GND

)

The power ground pin is used as a return for the
high-current N-Channel switch. The P

GND

 and S

GND

pins are connected externally. The signal ground and
power ground must be connected externally in one
point.

3.7

Enable Pin (EN)

The EN pin is a logic-level input used to enable or dis-
able device switching and lower quiescent current
while disabled. A logic high (>85% of V

IN

) will enable

the regulator output. A logic low (<7.5% of V

IN

) will

ensure that the regulator is disabled.

3.8

Exposed Thermal Pad (EP)

There is no internal electrical connection between the
Exposed Thermal Pad (EP) and the S

GND

 and P

GND

pins. They must be connected to the same potential on
the Printed Circuit Board (PCB).

3.9

Ground Pin (GND)

The ground or return pin is used for circuit ground con-
nection. The length of the trace from the input cap
return, the output cap return and the GND pin must be
as short as possible to minimize noise on the GND pin.
The 5-lead SOT-23 package uses a single ground pin.

TABLE 3-1:

PIN FUNCTION TABLE

MCP1662

SOT-23

MCP1662

2x3 TDFN

Symbol

Description

3

1

V

FB

Feedback Voltage Pin

2

S

GND

Signal Ground Pin

1

3

SW

Switch Node, Boost Inductor Input Pin

4, 6

NC

Not Connected

5

5

V

IN

Input Voltage Pin

7

P

GND

Power Ground Pin

4

8

EN

Enable Control Input Pin

9

EP

Exposed Thermal Pad (EP); must be connected to Ground

2

GND

Ground Pin

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 2014-2015 Microchip Technology Inc.

DS20005316E-page 9

MCP1662

4.0

DETAILED DESCRIPTION

4.1

Device Overview

The MCP1662 device is a fixed-frequency, synchro-
nous step-up converter, with a low-voltage reference of
300 mV, optimized to keep the output current constant
by regulating the voltage across the feedback resistor
(R

SET

). The MCP1662 integrates a peak current mode

architecture. It delivers high-efficiency conversion for
an LED lighting application when it is powered by two-
or three-cell alkaline, lithium, NiMH, NiCd, or single-cell
Lithium-Ion batteries. The maximum input voltage is
5.5V. A high level of integration lowers total system
cost, eases implementation and reduces board area.

The conventional boost converter with a high-voltage
reference has a high-voltage drop across the LED
series current limit resistor. The power dissipated in this
resistor, which is usually in series with the LED string,
reduces the total efficiency conversion of an LED driver
solution. Therefore, the voltage drop on the sense
resistor (R

SET

) that is used to regulate the LED current

must be low. In the case of MCP1662, the V

FB

 value is

300 mV.

The device features controlled start-up voltage
(UVLO

START

= 2.3V) and open load protection, in case

the LED fails or a short circuit of the V

FB

 pin to GND

occurs. If the V

FB

 voltage drops to 50 mV typical, the

device stops switching and the output voltage will be
equal to the input voltage (minus a diode drop voltage).
This feature prevents damage to the device and LEDs
when there is an accidental drop in voltage.

The 800 m

, 36V integrated switch is protected by the

1.3A cycle-by-cycle inductor peak current limit opera-
tion. When the Enable pin is pulled to ground
(EN = GND), the device stops switching, enters into
Shutdown mode and consumes less than 50 nA of
input current (

Figure 2-8

).

4.2

Functional Description

The MCP1662 is a compact, high-efficiency, fixed
500 kHz frequency, step-up DC-DC converter. It oper-
ates as a constant current generator for applications
powered by two- or three-cell alkaline or lithium Ener-
gizer

®

 batteries, or three-cell NiCd or NiMH batteries,

or one-cell Lithium-Ion or Li-Polymer batteries. 

Figure 4-1

 depicts the functional block diagram of the

MCP1662. It incorporates a Current mode control
scheme, in which the PWM ramp signal is derived from
the NMOS power switch current (V

SENSE

). This ramp

signal adds a slope ramp compensation signal (V

RAMP

)

and is compared to the output of the error amplifier
(V

ERROR

) to control the “on” time of the power switch.

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MCP1662

DS20005316E-page 10

 2014-2015 Microchip Technology Inc.

FIGURE 4-1:

MCP1662 Simplified Block Diagram.

EN

+

-

+

-

+

-

S

+

-

300 mV

V

FB

EA

GND

+

-

V

OLP_REF

V

FB

V

FB_FAULT

Cc

Rc

V

RAMP

V

ERROR

CLK

QN

V

EXT

V

FB

V

IN_OK

EN

V

BIAS

V

UVLO_REF

V

IN_OK

300 mV

V

UVLO_REF

V

SENSE

V

LIMIT

V

OUT_OK

V

IN

Internal Bias 

UVLO_COMP

SW

Overcurrent Comparator

Slope

Compensation

Oscillator

Gate Drive 

and

Shutdown 

Control 

Logic

Logic

SR Latch

Open Load Comparator

Thermal 

Shutdown

Power Good 

Comparator

and Delay

V

PWM

Bandgap

V

OLP_REF

+

+

REF

OC

Maker
Microchip Technology Inc.