SC4505EVB SEMTECH [Semtech Corporation], SC4505EVB Datasheet

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SC4505EVB

Manufacturer Part Number
SC4505EVB
Description
High Efficiency Boost Converter for Backlight/Flash LED Driver
Manufacturer
SEMTECH [Semtech Corporation]
Datasheet
The SC4505 is a high-frequency PWM current-mode step-
up switching regulator with an integrated 2A power tran-
sistor. Its high switching frequency (1MHz) allows the use
of tiny surface-mount external passive components. The
internal switch is rated at 36V which makes the con-
verter ideal for multiple LED series operation with opti-
mal current matching. Two programmable independent
current source structure allows dual panel LED backlight
and flash operation.
The operating frequency of the SC4505 is set at 1MHz.
The selected operating frequency gives the SC4505 de-
sign flexibility for size, cost and efficiency optimization.
The SC4505 is available in thermally enhanced 16-pin
MLPQ package (3x3x0.9mm) with embedded over tem-
perature protection.
POWER MANAGEMENT
Revision: December 15, 2006
Typical Application Circuit
Description
VIN: 2.6V ~ 6.0V
PGND
EN_BL
EN_FL
AGND
FL_TRB
RO1SET
6.98k
0
C2
2.2u
0.33uF
C3
RO2SET
1.54k
16
15
14
13
12
11
10
IHLP-2525CZ-01-1R5-M-01
9
VIN
FTO
FL_TRB
EN_FL
EN_BL
IO1SET
IO2SET
AGND
L1
Figure 1. SC4505 Application Circuit for Backlight and Flashlight LED Driver
PGND
PGND
COMP
SC4505
SW
SW
IO2
IO1
VO
1
2
3
4
5
6
7
8
Power
Ground
0
1.47k
R1
0
2
LED: SML-LX0603UWD
12n
10BQ015
C6
All Capacitors are Ceramic.
D1
Analog
Ground
1
2.2uF
C1
0
0
LED
LED
LED
D6
(Optional)
D2
D4
12n
C4
1
LED
D7
Features
LED
Applications
LED
D3
D5
0
Two independent current sources for dual LED strands
with optimal current/light matching. Backlight up to
75mA, Flash up to 125mA
Wide input range from 2.6V to 12V
Adaptive output voltage up to 28V with OVP protec-
tion against open circuit conditions
Low shutdown current (<1 A )
Internal Flash/Torch mode with flash timeout to pro-
tect LEDs
1MHz Fixed Frequency Current-Mode Control
Internal 2A current limit for driving large numbers of
LEDs
Supports PWM Dimming from 50Hz to 50kHz
Internal undervoltage lockout
Small, low profile, thermally enhanced 16-MLPQ pack-
age is fully WEEE and RoHS compliant
White LED power supplies
Flat screen LCD bias supplies
TFT bias supplies
Dual panel Handset/Liquid Crystal Display Monitor
Portable media players
Digital video cameras
Digital still cameras
High Efficiency Boost Converter
(Optional)
12n
C5
for Backlight/Flash LED Driver
87
85
83
81
79
77
Boost Converter Efficiency vs Input Voltage
2.5
(2 String of 3 LEDs @30mA)
3
Input Voltage (V)
3.5
4
www.semtech.com
SC4505
4.5
5

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SC4505EVB Summary of contents

Page 1

POWER MANAGEMENT Description The SC4505 is a high-frequency PWM current-mode step- up switching regulator with an integrated 2A power tran- sistor. Its high switching frequency (1MHz) allows the use of tiny surface-mount external passive components. The internal switch is rated ...

Page 2

POWER MANAGEMENT Absolute Maximum Rating Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions ...

Page 3

POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified 3.6V, -40°C < < 85° ...

Page 4

POWER MANAGEMENT Pin Configurations TOP VIEW (16 Pin - MLPQ) Block Diagram Thermal UVLO Shutdown Reference& Internal Regulator EN_BL BL Setpoint IO1SET RO1SET AGND 2006 Semtech Corp. Ordering Information ...

Page 5

POWER MANAGEMENT Pin Descriptions Block Diagram ...

Page 6

POWER MANAGEMENT Overview The SC4505 contains a 1MHz fixed-frequency, current- mode boost converter, and two independent LED current regulators. The LED current setpoints are chosen using external resistors, and the PWM controller operates independently to keep the two currents in ...

Page 7

POWER MANAGEMENT Applications Information Boost Converter Setup The SC4505 is a fixed-frequency, current mode step-up DC-DC converter that is ideal for driving LEDs in the applications in which both backlighting and flashlighting are needed. Unlike the ballasting resistor scheme, multiple ...

Page 8

POWER MANAGEMENT Applications Information 2.7V I 0.8A 1 µ 1.5 µ H When using tiny inductors for size-sensitive applications, only a few limited selections are available that fulfill this need, and all are within the low H range ...

Page 9

POWER MANAGEMENT Applications Information VENDOR PHONE KEMET 408-986-0424 Murata 814-237-1431 Taiyo Yuden 408-573-4150 Table 5. Recommended Ceramic Capacitor Manufacturers Output Rectifying Diode Selection Schottky diodes are the ideal choice for SC4505 due to their low forward voltage drop and fast ...

Page 10

POWER MANAGEMENT Applications Information An additional advantage of PWM dimming comes to customers who prefer to avoid inrush currents when filling the boost output capacitor – simply PWM the device at 10% duty for a millisecond or two, reducing inrush ...

Page 11

POWER MANAGEMENT Applications Information VIN L1 D1 SC4505 COMP V OVP Figure 5. OVP Tweaking As shown in Figure 5, R and R are the internal resistor 1 2 divider. R and R are ...

Page 12

POWER MANAGEMENT Applications Information Layout Guideline The SC4505 contains a boost converter. The placements of the power components outside the SC4505 should follow the guideline of general boost converter layout. The application circuit (Figure 7a) will be used as an ...

Page 13

POWER MANAGEMENT Applications Information To minimize switching noise for boost converter, the output capacitor, C3, should be placed right at the bottom as displayed in Figure 6b so that loop formed by C3, D5 and the SC4505 internal switch is ...

Page 14

POWER MANAGEMENT Typical Application Circuits P1 Vin=2.6~4.6V C2 2.2u P2 0.33uF C4 R1 100 R3 6.98k R6 R5 10k 10k Figure 7a Backlight and Flashlight LED driver for Figure 7b Efficiency Curve for ...

Page 15

POWER MANAGEMENT Outline Drawing - MLPQ - 16 PIN 1 INDICATOR (LASER MARK) aaa C NOTES: Land Pattern - MLPQ - 16 (C) NOTES: Contact Information 2006 Semtech Corp DIM ...

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