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MCP1643
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Datasheet MCP1643 Datasheet

MCP1643
MCP1643
2x3 DFN*
NC
V
FB
V
OUT
S
GND
P
GND
1 2 3
4
8 7 6
5
SW
V
IN
EN
EP
9
6
1 2
3
8
V
IN
P
GND
EN
V
FB
NC
7
S
GND
MCP1643
MSOP-8
5
4
SWV
OUT
* Includes Exposed Thermal Pad (EP), see Table 3-1.
1 MHz Low Start-up Voltage Synchronous Boost
LED Constant Current Regulator
Features
• 1.6A Typical Peak Input Current Limit
• Up to 550 mA LED Load Current
• Low Start-up Voltage: 0.65V (typical, 25 mA LED Current)
• Low Operating Input Voltage: down to 0.5V
• Maximum Output Voltage:
-5.0V
- Overvoltage Protection
• Low Reference Voltage:
-V
= 120 mV
FB
- Minimal Power Loss on Sense Resistor
• Pulse-Width Modulation Mode Operation (1 MHz)
• Internal Synchronous Rectifi er
• Internal Compensat ion
• Inrush Current Limiting
• Internal Soft-Start (240 µs typical)
• Shutdown (EN = GND):
- True Load Disconnect
- Dimming Control by Variable Duty Cycle
• Shutdown Current: 1.2 µA (typical)
• Overtemperature protection
• Packages:
- MSOP-8
- 2x3 DFN-8
LED
<5.0V
Applications
• One and Two Cell Alkaline and NiMH/NiCd Portable LED Lighting Products
• LED Flashlight and Head Lamps
• Rechargeable Flashlights
• Wall LED Lamp s with Motion Detectors
• LED supply for backlights
• General LED constant current applications
Description
MCP1643 is a compact, high-efficiency, fixed frequency , sy nchronous st ep-up converte r optimized to drive one LED with consta nt current, that operate s from one and two-cell alkaline and NiMH/NiCd batteries. The device can also drive two red/green/yellow series connection LEDs.
Low-voltage tec hnolo gy allo ws the regula tor to sta rt up without high-output v olt age a nd load -curren t overs hoot from a low 0.65V input. High ef ficiency is acco mplished by integrating the low resistance N-Channel Boost switch and synchronous P-Channel switch. All compensation and protection circuitry a re i nte grated to minimize external components.
The internal feedba ck (V low power dissipation when sensing and regulating LED current. A single resistor sets the constant current output that drives the LED load.
The device features an output overvoltage protection that limits the ou tput volt age to 5.0V typ ical, in ca se the LED fails or output load is disconnected.
The LED will either be turned OFF or turned ON using the enable input. A T rue Outpu t Load Disconne ct mode provides input-to-output isolation while Shutdown (EN = GND) by removing the normal boost regulator diode path from input to output. Shutdown state consumes 1.2 µA from input at room temperature.
The LED can be turned on and off with a variable duty cycle pulse-width modulation (PWM) signal applied to the EN pin for dimming applications.
The device also features a thermal shutdown at +150°C, with +25°C hysteresis.
Two package options, MSOP-8 and 2x3 DFN-8, are available.
) voltage is set to 120mV for
FB
Package Types
2013 Microchip Technology Inc. DS20005208A-page 1
10
100
1000
0.1
1
10
0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3
LED Current (mA)
R
SET
(Ω)
Input Voltage (V)
R
SET
for I
LED MIN
I
LED MIN
I
LED MAX
R
SET
for I
LED MAX
TA = +25oC
V
IN
GND
V
FB
C
OUT
4.7 µF
C
IN
4.7...10 µF
L
1
4.7 µH
SW
LED
4.7
EN
V
OUT
+
-
ALKALINE
ON
OFF
MCP1643
I
LED
=25mA
R
SET
V
IN
GND
V
FB
C
OUT
20 µF
C
IN
4.7...10 µF
L
1
4.7 µH
SW
WHITE LED
0.33
EN
V
OUT
+
-
NIMH 1.2V
ON/OFF
MCP1643
I
LED
=360mA
R
SET
+
-
NIMH 1.2V
1M
R
EN
I
LED
0.12V
R
SET
---------------- -=
R
SET
Minimum and Maximum Limits for I
LED
in Regulation, with ±6% Tolerance
WHITE LED
I
LED MAX
I
LED MIN
MCP1643
Typical Applications
DS20005208A-page 2 2013 Microchip Technology Inc.
MCP1643
1.0 ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings †
EN, FB, V
EN, FB .........< m ax im um V
Output Short Circuit Current.......................Continuous
IN, VSW
, V
- GND...........................+6.5V
OUT
or VIN>(GND–0.3V)
OUT
† 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 tho se or any oth er conditions ab ove those indicated in the operational sections of this specification is not intended. Exposure to maximum rating conditions for extended periods may affect
device reliability.
Power Dissipation ............................Internally Limited
Storage Temperature.........................-65°C to +150°C
Ambient Temp. with Power Applied......-40°C to +85°C
Operating Junction Temperature........-40°C to +125°C
ESD Protection On All Pins:
HBM ..............................................................4 kV
MM................................................................300V
DC CHARACTERISTICS
Electrica l Characteristics: Unless otherwise indicated, VIN= EN = 1.2V, C
I
=25mA, TA=+25°C. Boldface specifications apply over the TA range of -40°C to +85°C.
LED
Parameters Sym Min Typ Max Units Conditions
Input Characteristics
Minimum Input Voltage
V
IN
—0.5 — VNote 1, Note 3
After Start-Up Start-Up Voltage V Output Overvoltage
V
OUT_OVP
IN
—0.65 0.8 VNote 2, Note 1 —5.0 — VNote 3
Protection Shutdown
I
QSHDN
—1.2 — µAEN= GND;
Quiescent Current
Feedback Voltage V Feedback Input
I
VFB
FB
105 120 135 mV
—60 —pA
Bias Current NMOS Switch Leakage I
PMOS Switch Leakage I
NMOS Switch
R
NLK
PLK
DS(ON)N
—0.4 —µAV
—0.25 — µAVIN=VSW= GND;
—0.2 — I
ON Resistance PMOS Switch
R
DS(ON)P
—0.4 — I
ON Resistance NMOS Peak
I
N(MAX)
—1.6 — ANote 3
Switch Current Limit Maximum Duty Cycle DC Minimum Duty Cycle DC Switching Frequency f EN Input Logic High V EN Input Logic Low V
Note 1: For V
2: V
OUT
IN <VOUT
completely discharged. If the output capacitor remains partially charged, the device will start-up at
, I
remains in regulation up to V
LED
MAX
MIN
SW
IH IL
—90 —%Note 3 —5 —%Note 3
0.85 1.0 1.15 MHz 75 — — %of VINI —— 20%of VINI
IN =VLED
minus a headroom @ LED typical VF and IF.
the minimum possible voltage.
3: Determined by characterization, not production tested.
=20µF, CIN= 10 µF, L = 4.7µH,
OUT
includes N-Channel and P-Channel Switch Leakage
IN=VSW
V
OUT
V
EN=VFB
V
OUT
LED
LED
LED LED
=4.0V
=4.5V
=GND
=4.5V
= 250 mA, Note 3
= 250 mA, Note 3
=25mA
=25mA
2013 Microchip Technology Inc. DS20005208A-page 3
MCP1643
DC CHARACTERISTICS (CONTINUED)
Electrica l Characteristics: Unless otherwise indicated, VIN= EN = 1.2V, C
I
=25mA, TA=+25°C. Boldface specifications apply over the TA range of -40°C to +85°C.
LED
Parameters Sym Min Typ Max Units Conditions
EN Input Leakage Current I Soft Start Time t
ENLK
SS
—0.9 —µAVEN=1.2V — 240 — µs EN Low-to-H igh,
— 270 — µs EN Low-to-H igh,
Thermal Shutdown
T
SD
—150 — CI
Die Temperature Die Temperature
T
SDHYS
—25 —C
Hysteresis
Note 1: For V
2: V
OUT
IN <VOUT
remains in regulation up to V
LED
IN =VLED
completely discharged. If the output capacitor remains partially charged, the device will start-up at
minus a headroom @ LED typical VF and IF.
, I
the minimum possible voltage.
3: Determined by characterization, not production tested.
=20µF, CIN= 10 µF, L = 4.7µH,
OUT
90% of V I
LED
90% of V I
LED LED
OUT
=25mA, Note 3
OUT
=300mA, Note 3
=25mA
;
;
TEMPERATURE SPECIFICATIONS
Electrica l Characteristics: Unless otherwise indicated, VIN= EN = 1.2V, C
=25mA, TA=+25°C. Boldface specifications apply over the TA range of -40°C to +85°C.
I
LED
Parameters Sym Min Typ Max Units Conditions
Temperature Ranges
Operating Ambient Temperature Range T Storage Temperature Range T Maximum Junction Temperature T
A A
J
-40 — +85 °C Steady State
-65 — +150 °C — — +150 °C Transient
Package Thermal Resistances
Thermal Resistance, 8L-2x3 DFN Thermal Resistance, 8L-MSOP
JA JA
—68 —°C/W —211 —°C/W
=20µF, CIN= 10 µF, L = 4.7µH,
OUT
DS20005208A-page 4 2013 Microchip Technology Inc.
MCP1643
0
50
100
150
200
250
300
350
400
450
500
0.6 0.9 1.2 1.5 1.8 2.1 2.4
R
SET
= 5ȍ
R
SET
= 1.2ȍ
R
SET
= 0.82ȍ
R
SET
= 0.41ȍ
R
SET
= 0.25ȍ
LED VF= 3.5V @ IF= 700 mA
0
25
50
75
100
125
150
175
200
225
250
0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
LED Current (mA)
R
SET
= 5ȍ
LED VF= 2.5V @ IF= 350 mA
R
SET
= 1.2ȍ
R
SET
= 0.82ȍ
0
50
100
150
200
250
300
350
0.6 0.9 1.2 1.5 1.8 2.1 2.4
R
SET
= 5ȍ
R
SET
= 1.2ȍ
R
SET
= 0.82ȍ
R
SET
= 0.41ȍ
LED VF= 2.5V @ IF= 350 mA
60
65
70
75
80
85
90
95
100
10 100 1000
Efficiency (%)
VIN= 1.2V
VIN= 1.8V
VIN= 2.4V
70
75
80
85
90
95
100
10 100 1000
VIN= 1.2V
VIN= 1.8V
VIN= 2.4V
50
55
60
65
70
75
80
85
90
95
100
10 100 1000
Efficiency (%)
VIN= 3.0V
VIN= 2.4V
VIN= 3.6V

2.0 TYPICAL PERFORMANCE CURVES

Note: The graphs and table s pro vi ded follo w ing this note ar e a st a tis tic al sum ma ry ba sed 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.
Note: Unless otherwise indicated, VIN=EN=1.2V, C MSOP-8 package.
LED Current (mA)
Input Voltage (V)
FIGURE 2-1: One White LED I
LED
vs. VIN.
=20µF, CIN= 10 µF, L = 4.7 µH, I
OUT
FIGURE 2-4: One White LED Efficiency vs. I
LED
Efficiency (%)
.
=25mA, TA=+25°C,
LED
I
(mA)
LED
FIGURE 2-2: One Red LED I
LEDs Current (mA)
FIGURE 2-3: Two Series Connection Red LEDs I
2013 Microchip Technology Inc. DS20005208A-page 5
LED
vs. VIN.
Input Voltage (V)
Input Voltage (V)
LED
vs. VIN.
I
(mA)
LED
FIGURE 2-5: One Red LED Efficiency vs.
.
I
LED
I
(mA)
LED
FIGURE 2-6: Two Red LEDs Efficiency (in Series Connection) vs. I
LED
.
MCP1643
0
50
100
150
200
250
300
350
-40 -25 -10 5 20 35 50 65 80
R
SET
= 5ȍ
R
SET
= 1.2ȍ
R
SET
= 0.82ȍ
R
SET
= 0.41ȍ
VIN= 1.5V
0
25
50
75
100
125
150
0 102030405060708090100
R
SET
= 0.82ȍ
VIN= 1.5V
fEN= 400 Hz
fEN= 1 kHz
34
35
36
37
38
39
40
-40 -25 -10 5 20 35 50 65 80
Duty Cycle (%)
R
SET
= 1.2ȍ
(I
LED
= 100 mA)
0
100
200
300
400
500
600
700
0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3
TA= +85oC
TA= +25oC
TA= 0oC
980
985
990
995
1000
1005
1010
-40 -25 -10 5 20 35 50 65 80
Switching Frequency (kHz)
I
LED
= 100 mA
117
118
119
120
121
122
123
-40 -25 -10 5 20 35 50 65 80
I
LED
= 100 mA
Note: Unless otherwise indicated, VIN=EN=1.2V, C MSOP-8 package.
LED Current (mA)
Ambient Temperature (°C)
FIGURE 2-7: One White I
vs. Ambient
LED
Temperature.
=20µF, CIN= 10 µF, L = 4.7 µH, I
OUT
LED Current (mA)
FIGURE 2-10: Maximum I
=25mA, TA=+25°C,
LED
Input Voltage (V)
LED
vs. VIN.
LED Current (mA)
Duty Cycle (%)
FIGURE 2-8: I
vs. VEN Duty Cycle.
LED
Ambient Temperature (°C)

FIGURE 2-9: Duty Cycle vs. Ambient Temperature.

Ambient Temperature (°C)
FIGURE 2-11: f Temperature.
Feadback Voltage (mV)
Ambient Temperature (°C)
FIGURE 2-12: V Temperature.
vs. Ambient
SW
vs. Ambient
FB
DS20005208A-page 6 2013 Microchip Technology Inc.
MCP1643
VEN
80 us/div
1 V/div
V
IN
I
LED
20 mA/div
20 mV/div, AC Coupled
V
OUT
1 V/div
V
SW
I
LED
100 mA/div
1us/div
I
LED
50 mA/div
1 V/div
V
SW
1 V/div
V
EN
400 us/div
80 us/div
500 mA/div
IL
1 V/div
V
IN
I
LED
20 mA/div
I
LED
50 mA/div
1 V/div
V
SW
1 V/div
V
EN
400 us/div
I
LED
10 ms/div
2 V/div
Step from I
LED
= 100 mA to Open Load
2 V/div
100 mA/div
V
OUT
V
SW
2V
5V
Note: Unless otherwise indicated, VIN=EN=1.2V, C
MSOP-8 package.

FIGURE 2-13: Start-up After Enable.

=20µF, CIN= 10 µF, L = 4.7 µH, I
OUT

FIGURE 2-16: Start-up when VIN=VEN.

=25mA, TA=+25°C,
LED

FIGURE 2-14: 100 mA PWM Operation.

FIGURE 2-15: 400 Hz PWM Dimming,
85% Duty Cycle.
2013 Microchip Technology Inc. DS20005208A-page 7

FIGURE 2-17: 400 Hz PWM Dimming, 15% Duty Cycle.

FIGURE 2-18: Open Load Response.

MCP1643
NOTES:
DS20005208A-page 8 2013 Microchip Technology Inc.
MCP1643

3.0 PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1: PIN FUNCTION TABLE

MCP1643
2x3 DFN
1 1 EN Enable pin. The logic high enables the operation. Do not allow this pin to
22V
3 3 NC Unconnected pin 44V
5 5 SW Boost and Rectifier Switch Input pin. Connect the boost inductor between
66P 77S 88VINInput Sup ply Voltage pin. A local bypass capacitor is required. 9 — EP Exposed Thermal Pad, must be connected to V
MCP1643
MSOP
Symbol Description
float.
FB
OUT
GND GND
Reference Voltage pin. Connect to the VFB pin, the R resistor), and the cathode of the LED load.
Boost Converter Output pin. Connect to this pin the anode of the LED load. An output filter capacitor is required.
SW and V Power Ground Reference pin Signal Ground Reference pin
.
IN
SS
(LED current set
SET

3.1 Enable Pin (EN)

The EN pin is a logic-level input used to enable or disable device switching. Device has low quiescent current while disabled. A logic high (>75% of VIN) will enable the regulator output. A logic low (<20% of V will ensure that the regulator is disabled.
IN

3.2 Feedback Voltage Pin (VFB)

The VFB pin is used to r egu lat e the vo ltage acr oss t he R
sense resistor to 120 mV , to keep the outp ut LED
SET
current in regulation.

3.3 Unconnected Pin (NC)

This pin is unconnected.
3.4 Output Voltage Power Pin (V
High current flows through the integrated P-Channel and out of this pin to the output cap acitor , LED load and
sense resistor. The output voltage must be
R
SET
filtered using a 4.7 to 20 µF X7R or X5R ceramic capacitor. The value of t he output capacitor de pends on the load current.
OUT
)

3.5 Switch Node Pin (SW)

3.6 Power Ground (P Ground Pins (S
The power gr ound pins are used as a r eturn for the high-current N-Channel switch.
)
The signal ground pin is used as a return for the integrated V
The length of the trace from input cap return, output cap return and P short as possible to min imize noi se on the grou nd pins.
The S
GND
and error amplifier.
FB
and S
GND
and P
pins are connected externally.
GND
GND
) and Signal
GND
)
GND
should be made as
3.7 Power Supply Input Voltage Pin (V
)
IN
Connect the input voltage source to VIN. The input source should be decoupled to GND with a 4.7 µF minimum capac itor.

3.8 Exposed Thermal Pad (EP)

There is no internal electrical connection between the Exposed Thermal Pad (EP) and the P pins. They must be conn ected to the same poten tia l on the Printed Circuit Board (PCB).
GND
and S
GND
Connect the inductor from the input voltage to the SW pin. The SW pin carries inductor current and can be as high as 1.6 A typical peak value. The integrated N-Channel switch drain and integrated P-Channel switch source are intern ally connect ed at the SW node.
2013 Microchip Technology Inc. DS20005208A-page 9
MCP1643
NOTES:
DS20005208A-page 10 2013 Microchip Technology Inc.
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