SEMTECH SC627

SC627
LED Light Management Unit
Charge Pump, 4 LEDs, 700mA Flash LED,
Dual LDOs, and SemWireTM Interface
POWER MANAGEMENT
Features
Description
„
The SC627 is a high efficiency charge pump LED driver
using Semtech’s proprietary mAhXLifeTM technology.
Performance is optimized for use in single-cell Li-ion
battery applications.
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Input supply voltage range — 3.0V to 5.5V
Charge pump modes — 1x, 1.5x and 2x
Four programmable current sinks with 32 steps from
0.5mA to 25mA
Flash LED — 700mA max in flash mode, 250mA max
continuous for spotlight
Two user-configurable 100mA low-noise LDO
regulators
Charge pump frequency — 250kHz
SemWireTM single wire interface — up to 75kbit/s
Backlight current accuracy ±1.5% typical
Backlight current matching ±0.5% typical
Programmable fade-in/fade-out for main backlight
External flash control pin to sync with camera
Optional 1s flash time out
Automatic sleep mode (LEDs off ) — IQ = 100μA
Low shutdown current — 0.1μA (typical)
Ultra-thin package — 3mm x 3mm x 0.6mm
Fully WEEE and RoHS compliant
The charge pump provides backlight current in
conjunction with four matched current sinks. It also can
supply continuous or bursted current to a flash LED using
the dedicated flash driver current sink. The load and
supply conditions determine whether the charge pump
operates in 1x, 1.5x, or 2x mode. An optional fading feature
that gradually adjusts the backlight current is provided to
simplify control software. A flash-timeout feature disables
the flash if active for longer than 1 second. The SC627 also
provides two low-dropout, low-noise linear regulators for
powering a camera module or other peripheral circuits.
The SC627 uses the proprietary SemWireTM single wire
interface. The interface controls all functions of the
device, including backlight and flash currents as well as
two LDO voltage outputs. The single wire implementation
minimizes microcontroller and interface pin counts. The
flash/spotlight output is triggered via either the SemWire
interface or a dedicated pin.
Applications
„
Cellular phone backlighting and flash
„ PDA backlighting and flash
„ Camera I/O and core power
In sleep mode, the device reduces quiescent current to
100μA while continuing to monitor the serial interface.
The two LDOs can be enabled when the device is in sleep
mode. Total current reduces to 0.1μA in shutdown.
Typical Application Circuit
MAIN BACKLIGHT
VIN
VBAT
CIN
2.2μF
SemWire
Interface
Flash
Control
VOUT
SC627
GREF
BL1
BL2
BL3
BL4
FL
AGND
LDO1
PGND
LDO2
BYP
CBYP
22nF
COUT
4.7μF
SWIF
FLEN
C1+ C1C1
2.2μF
FLASH
C2+ C2-
VLDO1 = 2.5V to 3.3V
VLDO2 = 1.5V to 1.8V
CLDO1
1.0μF
CLDO2
1.0μF
C2
2.2μF
US Patents: 6,504,422; 6,794,926
June 27, 2007
© 2007 Semtech Corporation
1
SC627
C2-
VIN
C1+
C2+
VOUT
Ordering Information
C1-
Pin Configuration
20
19
18
17
16
1
15
LDO1
TOP VIEW
PGND
2
14
LDO2
FL
3
13
BYP
BL1
4
12
NC
BL2
5
11
SWIF
6
7
8
9
10
BL3
BL4
AGND
GREF
FLEN
T
Device
Package
SC627ULTRT(1)(2)
MLPQ-UT-20 3×3
SC627EVB
Evaluation Board
Notes:
(1) Available in tape and reel only. A reel contains 3,000 devices.
(2) Available in lead-free package only. Device is WEEE and RoHS
compliant.
MLPQ-UT-20; 3x3, 20 LEAD
θJA = 35°C/W
Marking Information
627
yyww
xxxx
yyww = Date Code
xxxx = Semtech Lot No.
2
SC627
Absolute Maximum Ratings
Recommended Operating Conditions
VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0
Ambient Temperature Range (°C) . . . . . . . . -40 < TA < +85
VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0
VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 < VIN < 5.5
C1+, C2+ (V) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to (VOUT + 0.3)
VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 < VOUT < 5.25
Pin Voltage - All Other Pins (V) . . . . . . . . . . . -0.3 to (VIN + 0.3)
Voltage Difference between any two LEDs (V) . . . . . . < 1.2
VOUT Short Circuit Duration . . . . . . . . . . . . . . . . Continuous
VLDO1, VLDO2, Short Circuit Duration . . . . . . Continuous
ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Thermal Information
Thermal Resistance, Junction to Ambient(2) (°C/W) . . . . 35
Maximum Junction Temperature (°C) . . . . . . . . . . . . . . +150
Storage Temperature Range (°C) . . . . . . . . . . . . -65 to +150
Peak IR Reflow Temperature (10s to 30s) (°C) . . . . . . . +260
Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not recommended.
NOTES:
(1) Tested according to JEDEC standard JESD22-A114-B.
(2) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
Electrical Characteristics
Unless otherwise noted, TA = +25°C for Typ, -40ºC to +85°C for Min and Max, TJ(MAX) = 125ºC, VIN = 3.0V to 4.2V, CIN= C1= C2= 2.2μF,
COUT = 4.7μF (ESR = 0.03Ω), ΔVF ≤ 1.2V(1)
Parameter
Symbol
Conditions
IQ(OFF)
Min
Typ
Max
Units
Shutdown, VIN = 4.2V
0.1
2
μA
Sleep (LDOs off ), SWIF = VIN
100
160
Sleep (LDOs on), SWIF = VIN,
VIN > (VLDO + 300mV), ILDO < 200mA
220
340
Charge pump in 1x mode, 4 backlights on
3.8
4.65
Charge pump in 1.5x mode, 4 backlights on
4.6
5.85
Charge pump in 2x mode, 4 backlights on
4.6
5.85
VOUT pin shorted to GND
300
mA
160
°C
Supply Specifications
Shutdown Current
Total Quiescent Current
IQ
μA
mA
Fault Protection
Output Short Circuit
Current Limit
Over-Temperature
Flash Mode Safety Timer(2)
IOUT(SC)
TOTP
tFL(MAX)
Flash sink active
0.75
1.00
1.25
s
3
SC627
Electrical Characteristics (continued)
Parameter
Symbol
Conditions
Min
Typ
Max
Units
VOVP
VOUT pin open circuit, VOUT = VOVP
rising threshold
5.3
5.7
6.0
V
VUVLO
Decreasing VIN
Fault Protection (continued)
Charge Pump
Over-Voltage Protection
2.4
V
300
mV
Undervoltage Lockout
VUVLO-HYS
Charge Pump Electrical Specifications
Maximum Total Output
Current
IOUT(MAX)
VIN > 3.4V, sum of all active LED currents,
VOUT(MAX) = 4.0V
800
Backlight Current Setting
IBL
Nominal setting for BL1 thru BL4
0.5
25
mA
Flash Current Setting
IFL
Nominal setting for FL
50
700
mA
Backlight Current Accuracy
IBL_ACC
VIN = 3.7V, IBL = 12mA, TA = 25°C
-8
±1.5
+8
%
Backlight Current Matching
IBL-BL
VIN = 3.7V, IBL = 12mA(3)
-3.5
±0.5
+3.5
%
Flash Current Accuracy
IFL_ACC
VIN = 3.7V, IFL = 500mA, TA = 25°C
-15
+15
%
1x Mode to 1.5x Mode
Falling Transition Voltage
V TRANS1x
IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V
3.27
V
1.5x Mode to 1x Mode
Hysteresis
VHYST1x
IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V
250
mV
1.5x Mode to 2x Mode
Falling Transition Voltage
V TRANS1.5x
IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4)
2.92
V
2x Mode to 1.5x Mode
Hysteresis
VHYST1.5x
IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4)
300
mV
Current Sink Off-State
Leakage Current
IBLn
VIN = VBLn = 4.2V
0.1
fPUMP
VIN = 3.2V
250
LDO1 Voltage Setting
VLDO1
Range of nominal settings
in 100mV increments
2.5
3.3
V
LDO2 Voltage Setting
VLDO2
Range of nominal settings
in 100mV increments
1.5
1.8
V
LDO1, LDO2 Output
Voltage Accuracy
VLDO1, VLDO2
VIN = 3.7V, ILDO = 1mA
-3.5
±3
+3.5
%
2.1
7.2
Pump Frequency
mA
1
μA
kHz
LDO Electrical Specifications
LDO1, ILDO1 = 1mA, VOUT = 2.8V
Line Regulation
ΔVLINE
mV
LDO2, ILDO2 = 1mA, VOUT = 1.8V
1.3
4.8
4
SC627
Electrical Characteristics (continued)
Parameter
Symbol
Conditions
Min
Typ
Max
Units
LDO Electrical Specifications (continued)
Load Regulation
ΔVLOAD
Dropout Voltage(5)
VD
Current Limit
ILIM
Power Supply
Rejection Ratio
25
VLDO2 = 1.8V, VIN = 3.7V,
ILDO2 = 1mA to 100 mA
20
mV
ILDO1 = 100mA
100
150
200
mV
mA
PSRRLDO1
2.5V < VLDO1 < 3V, f < 1kHz, CBYP = 22nF, ILDO1 = 50mA,
VIN = 3.7V with 0.5VP-P ripple
50
PSRRLDO2
f < 1kHz, CBYP = 22nF, ILDO2 = 50mA,
VIN = 3.7V with 0.5VP-P ripple
60
en-LDO1
LDO1, 10Hz < f < 100kHz, CBYP = 22nF, CLDO = 1μF,
ILDO1 = 50 mA, VIN = 3.7V, 2.5V < VLDO1 < 3V
100
en-LDO2
LDO2, 10Hz < f < 100kHz, CBYP = 22nF, CLDO = 1μF,
ILDO2 = 50 mA, VIN = 3.7V
50
Output Voltage Noise
Minimum Output Capacitor
VLDO1 = 3.3V, VIN = 3.7V,
ILDO1 = 1mA to 100 mA
dB
μVRMS
CLDO(MIN)
1
μF
Digital I/O Electrical Specifications (FLEN, SWIF)
Input High Threshold
VIH
VIN = 5.5V
Input Low Threshold
VIL
VIN = 3.0V
Input High Current
IIH
VIN = 5.5V
Input Low Current
IIL
VIN = 5.5V
SemWire Bit Rate
1.6
V
0.4
V
-1
+1
μA
-1
+1
μA
fSWIF
10
75
kbit/s
SemWire Start-up Time(6)
tEN
1
ms
SemWire Disable Time(7)
tDIS
10
ms
SemWire Data Latch Delay(8)
DDL
5
bit
Notes:
(1) ΔVF is the voltage difference between any two LEDs.
(2) Once tripped, flash output will remain disabled until FLEN pin is cycled or reset via serial interface.
(3) Current matching equals ± [IBL(MAX) - IBL(MIN] / [IBL(MAX) + IBL(MIN)].
(4) Test voltage is VOUT = 4.0V — a relatively extreme LED voltage — to force a transition during test. Typically VOUT = 3.2V for white LEDs.
(5) Dropout is defined as (VIN - VLDO1) when VLDO1 drops 100mV from nominal. Dropout does not apply to LDO2 since it has a maximum output voltage
of 1.8V.
(6) The SemWire start-up time is the minimum period that the SWIF pin must be held high to enable the part before commencing
communication.
(7) The SemWire disable time is the minimum period that the SWIF pin must be pulled low to shut the part down.
(8) The SemWire data latch delay is the maximum duration after communication has ended before the register is updated.
5
SC627
Typical Characteristics
Battery Current (4 LEDs) — 25mA Each
160
Battery Current (4 LEDs) — 12mA Each
VOUT=3.66V, IOUT=100mA, 25°C
80
73
Battery Current (mA)
Battery Current (mA)
150
140
130
120
66
59
52
110
100
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
45
4.2
3.0
Backlight Efficiency (4 LEDs) — 25mA Each
100
100
% Efficiency
% Efficiency
3.8
3.6
VIN (V)
3.4
3.2
3.0
VOUT=3.50V, IOUT=48mA, 25°C
90
80
70
80
70
60
60
50
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
50
4.2
3.0
3.8
3.6
3.4
3.2
3.0
Backlight Efficiency (4 LEDs) — 5.0mA Each
VOUT=3.33V, IOUT=20mA, 25°C
100
35
VOUT=3.33V, IOUT=20mA, 25°C
% Efficiency
90
30
25
80
70
60
20
15
4.2
4.0
VIN (V)
Battery Current (4 LEDs) — 5.0mA Each
Battery Current (mA)
4.0
Backlight Efficiency (4 LEDs) — 12mA Each
VOUT=3.66V, IOUT=100mA, 25°C
90
40
VOUT=3.50V, IOUT=48mA, 25°C
4.0
3.8
3.6
VIN (V)
3.4
3.2
3.0
50
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
3.0
6
SC627
Typical Characteristics (continued)
Flash Current — 400mA
Flash Current — 700mA
VOUT=3.39V at 25°C
490
1000
900
Flash Current (mA)
Flash Current (mA)
460
VOUT=3.49V at 25°C
430
400
370
340
800
700
600
500
310
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
400
4.2
3.0
Spotlight Current — 50mA
53
340
3.4
3.2
3.0
3.2
3.0
VOUT=3.50V at 25°C
310
Spotlight Current (mA)
Spotlight Current (mA)
3.6
VIN (V)
Spotlight Current — 250mA
VOUT=3.02V at 25°C
52
51
50
49
48
280
250
220
190
47
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
160
4.2
3.0
0
VIN=3.7V at 25°C, ILDO1=50mA, VLDO1=2.8V
0
-10
-20
-20
PSRR (dB)
-10
-30
-40
-60
-60
-70
1000
Frequency (Hz)
3.6
VIN (V)
3.4
10000
VIN=3.7V at 25°C, ILDO2=50mA, VLDO2=1.8V
-40
-50
100
3.8
-30
-50
10
4.0
PSRR vs. Frequency (LDO2)
PSRR vs. Frequency (LDO1)
PSRR (dB)
3.8
4.0
-70
10
100
Frequency (Hz)
1000
10000
7
SC627
Typical Characteristics (continued)
Load Regulation (LDO2)
Load Regulation (LDO1)
24
VLDO1=3.3V, VIN=3.7V, 25°C
24
16
Output Voltage Variation (mV)
Output Voltage Variation (mV)
16
VLDO2=1.8V, VIN=3.7V, 25°C
8
0
-8
-16
8
0
-8
-16
-24
-24
0
30
60
90
120
150
0
ILDO1(mA)
100
80
60
Noise (μV)
Noise (μV)
VLDO1=2.8V, VIN=3.7V, 25°C
80
70
60
150
40
20
0
20
40
60
80
0
100
0
20
2
Output Voltage Variation (mV)
1
0
-1
-2
4.0
3.8
3.6
VIN (V)
60
80
100
Line Regulation (LDO2)
VLDO1=2.8V, ILDO1=1mA, 25°C
-3
4.2
40
ILDO2 (mA)
Line Regulation (LDO1)
Output Voltage Variation (mV)
120
VLDO2=1.8V, VIN=3.7V, 25°C
ILDO1 (mA)
2
90
Noise vs Load Current (LDO2)
90
50
60
ILDO2(mA)
Noise vs Load Current (LDO1)
100
30
3.4
3.2
3.0
VLDO2=1.8V, ILDO2=1mA, 25°C
1
0
-1
-2
-3
4.2
4.0
3.8
3.6
VIN (V)
3.4
3.2
3.0
8
SC627
Typical Characteristics (continued)
Load Transient Response (LDO1) — Rising Edge
Load Transient Response (LDO2) — Rising Edge
VIN=3.7V, VLDO1=2.8V, ILDO1=1 to 100mA
VIN=3.7V, VLDO2=1.8V, ILDO2=1 to 100mA
VLDO1 (50mV/div)
VLDO2 (50mV/div)
ILDO1 (100mA/div)
ILDO2 (100mA/div)
Time (20μs/div)
Load Transient Response (LDO1) — Falling Edge
Time (20μs/div)
Load Transient Response (LDO2) — Falling Edge
VIN=3.7V, VLDO2=1.8V, ILDO2=100 to 1mA
VIN=3.7V, VLDO1=2.8V, ILDO1=100 to 1mA
VLDO1 (50mV/div)
VLDO2 (50mV/div)
ILDO1 (100mA/div)
ILDO2 (100mA/div)
Time (200μs/div)
Time (200μs/div)
9
SC627
Typical Characteristics (continued)
Output Short Circuit Current Limit
Flash Mode Safety Timer
VOUT=0V, VIN=4.2V, 25°C
VOUT (1V/div)
VIN=3.7V, 25°C
VFLEN (5V/div)
VOUT (2V/div)
IOUT (100mA/div)
IFL (200mA/div)
Time (1ms/div)
Time (200ms/div)
Output Open Circuit Protection
Flash Current Pulse
IFL=400mA, VIN=3.7V, VOUT=3.7V, 25°C
VIN=3.7V, 25°C
VBL1 (500mV/div)
VFLEN (5V/div)
VOUT (2V/div)
VOUT (2V/div)
IBL1 (20mA/div)
IFL (200mA/div)
Time (200μs/div)
Time (40ms/div)
10
SC627
Pin Descriptions
Pin #
Pin Name
Pin Function
1
C2-
2
PGND
3
FL
Current sink output for flash LED(s)
4
BL1
Current sink output for main backlight LED 1 — leave this pin open if unused
5
BL2
Current sink output for main backlight LED 2 — leave this pin open if unused
6
BL3
Current sink output for main backlight LED 3 — leave this pin open if unused
7
BL4
Current sink output for main backlight LED 4 — leave this pin open if unused
8
AGND
Analog ground pin — connect to ground and separate from PGND current
9
GREF
Ground reference — connect to ground
10
FLEN
Control pin for flash LED(s) — high = ON, low = OFF
11
SWIF
SemWire single wire interface pin — used to enable/disable the device and to
set up all internal registers (refer to Register Map and SemWire Interface sections)
12
NC
Unused pin — do not terminate
13
BYP
Bypass pin for voltage reference — connect with a 22nF capacitor to AGND
14
LDO2
Output of LDO2 — connect with a 1μF capacitor to AGND
15
LDO1
Output of LDO1 — connect with a 1μF capacitor to AGND
16
VOUT
Charge pump output — all LED anode pins should be connected to this
pin — requires a 4.7μF capacitor to PGND
17
C2+
Positive connection to bucket capacitor 2 — requires a 2.2μF capacitor connected to C2-
18
C1+
Positive connection to bucket capacitor 1 — requires a 2.2μF capacitor connected to C1-
19
VIN
Battery voltage input — connect with a 2.2μF capacitor to PGND
20
C1-
Negative connection to bucket capacitor 1 — requires a 2.2μF capacitor
connected to C1+
T
THERMAL PAD
Negative connection to bucket capacitor 2 — requires a 2.2μF capacitor
connected to C2+
Ground pin for high current charge pump and Flash LED driver
Thermal pad for heatsinking purposes — connect to ground plane using multiple
vias — not connected internally
11
SC627
Block Diagram
VIN
SWIF
19
VIN
11
FLEN
10
GREF
9
SemWireTM
Digital
Interface
and Logic
Control
C1+
C1-
C2+
C2-
18
20
17
1
VOUT
mAhXLifeTM Fractional
Charge Pump
(1x, 1.5x, 2x)
13
Bandgap
Reference
Voltage
Setting
DAC
12
PGND
4
BL1
5
BL2
6
BL3
7
BL4
3
FL
15
LDO1
14
LDO2
VIN
LDO2
AGND
2
VIN
LDO1
NC
VOUT
Oscillator
Current
Setting
DAC
BYP
16
8
12
SC627
Applications Information
General Description
This design is optimized for handheld applications
supplied from a single Li-Ion cell and includes the
following key features:
•
•
•
•
•
A high efficiency fractional charge pump that
supplies power to all LEDs
Four matched current sinks that control LED
backlighting current, with 0.5mA to 25mA per
LED
An LED flash output that provides up to 700mA
of momentary current or up to 250mA of
continuous spotlight current
Two adjustable LDOs with outputs ranging from
2.5V to 3.3V for LDO1 and 1.5V to 1.8V for LDO2,
adjustable in 100mV increments
A SemWire single wire interface that provides
control of all device functions
High Current Fractional Charge Pump
The backlight and flash outputs are supported by a high
efficiency, high current fractional charge pump output
at the VOUT pin. The charge pump multiplies the input
voltage by 1, 1.5, or 2 times. The charge pump switches
at a fixed frequency of 250kHz in 1.5x and 2x modes
and is disabled in 1x mode to save power and improve
efficiency.
The mode selection circuit automatically selects the
1x, 1.5x or 2x mode based on circuit conditions. Circuit
conditions such as low input voltage, high output current,
or high LED voltage place a higher demand on the charge
pump output. A higher numerical mode may be needed
momentarily to maintain regulation at the VOUT pin
during intervals of high demand, such as the high current
of an LED flash or the droop at the VIN pin during a supply
voltage transient. The charge pump responds to these
momentary high demands, setting the charge pump to
the optimum mode (1x, 1.5x or 2x), as needed to deliver
the output voltage and load current while optimizing
efficiency. Hysteresis is provided to prevent mode
toggling.
between the C1+ and C1- pins and the other must be
connected between the C2+ and C2- pins as shown in
the typical application circuit diagram. These capacitors
should be equal in value, with a minimum capacitance of
2.2μF to support the charge pump current requirements.
The device also requires a 2.2μF capacitor on the VIN
pin and a 4.7μF capacitor on the VOUT pin to minimize
noise and support the output drive requirements.
Capacitors with X7R or X5R ceramic dielectric are strongly
recommended for their low ESR and superior temperature
and voltage characteristics. Y5V capacitors should not
be used as their temperature coefficients make them
unsuitable for this application.
LED Backlight Current Sinks
The backlight current is set via the SemWire interface.
The current is regulated to one of 32 values between
0.5mA and 25mA. The step size varies depending upon
the current setting. Between 0.5mA and 12mA, the
step size is 0.5mA. The step size increases to 1mA for
settings between 12mA and 15mA and 2mA for settings
greater than 15mA. This feature allows finer adjustment
for dimming functions in the low current setting range
and coarse adjustment at higher current settings where
small current changes are not visibly noticeable in LED
brightness.
All backlight current sinks have matched currents, even
when there is variation in the forward voltages (ΔVF )
of the LEDs. A ΔVF of 1.2V is supported when the input
voltage is at 3.0V. Higher ΔVF LED mis-match is supported
when VIN is higher than 3.0V. All current sink outputs are
compared and the lowest output is used for setting the
voltage regulation at the VOUT pin. This is done to ensure
that sufficient bias exists for all LEDs, including the flash
LED.
The backlight LEDs default to the off state upon powerup. For backlight applications using less than four LEDs,
any unused output must be left open and the unused
LED driver must remain disabled. When writing to the
Backlight Enable Control register, a zero (0) must be
written to the corresponding bit of any unused output.
The charge pump requires two bucket capacitors for
low ripple operation. One capacitor must be connected
13
SC627
Applications Information (continued)
Backlight Quiescent Current
Programmable LDO Outputs
The quiescent current required to operate all four
backlights is reduced by 1.5mA when backlight current
is set to 4.0mA or less. This feature results in higher
efficiency under light-load conditions. Further reduction
in quiescent current will result from using fewer than four
LEDs.
Two low dropout (LDO) regulators are provided for
camera module I/O and core power. Each LDO has at least
100mA of available load current with ±3.5% accuracy. The
minimum current limit is 200mA, so outputs greater than
100mA are possible at somewhat reduced accuracy.
Fade-In and Fade-Out
Backlight brightness can be set to automatically fade-in
when current is set to increase and fade-out when current
is set to decrease. When enabled with a new current
setting, the current will step through each incremental
setting between the old and new values. The result is a
visually smooth change in brightness with a rate of fade
that can be set to 8, 16, 24, or 32 ms per step.
LED Flash and Spotlight Current Sink
A single output current sink is provided to drive both flash
and spotlight functions. In flash mode, this current sink
provides up to 700mA for a flash LED or array of parallel
LEDs. Flash current settings are in 50mA increments from
50mA to 700mA. The FLEN pin directly triggers the FLASH
function when pulled high, or it can be wired to VIN to
enable software control via the serial interface.
In spotlight mode, the output can be set for up to 250mA
of continuous current. Settings are available in 50mA
increments from 50mA to 250mA. Continuous operation
above 250mA is not recommended due to high power
dissipation.
Flash and Spotlight Safety Timer
A safety timer disables the flash and spotlight output
current sink if the sink remains active for an extended
period. The timer protects the SC627 and the LED from
high power dissipation that can cause overheating. The
timer’s default state is on, but the timer may be disabled
via the serial interface to allow continuous output current
in spotlight mode. The safety timer affects only the FL pin
and will turn off the sink after a period of 1 second. The
timer may be reset by either forcing the FLEN pin low
or by resetting the Flash/Spotlight control bits via the
interface.
A 1μF, low ESR capacitor should be used as a bypass
capacitor on each LDO output to reduce noise and
ensure stability. In addition, it is recommended that a
minimum 22nF capacitor be connected from the BYP
pin to ground to minimize noise and achieve optimum
power supply rejection. A larger capacitor can be used
for this function, but at the expense of increasing turnon time. Capacitors with X7R or X5R ceramic dielectric
are strongly recommended for their low ESR and superior
temperature and voltage characteristics. Y5V capacitors
should not be used as their temperature coefficients
make them unsuitable for this application.
Shutdown State
The device is disabled when the SWIF pin is low. All
registers are reset to default condition when SWIF is low.
Sleep Mode
When all LEDs are off, sleep mode is activated. This is a
reduced current mode that helps minimize overall current
consumption by turning off the clock and the charge
pump while continuing to monitor the serial interface for
commands. Both LDOs can be powered up while in sleep
mode.
SemWire Single Wire Interface Functions
All device functions can be controlled via the SemWire
single wire interface. The interface is described in detail
in the SemWire Interface section of the datasheet.
14
SC627
Applications Information (continued)
Protection Features
The SC627 provides several protection features to
safeguard the device from catastrophic failures. These
features include:
•
•
•
•
•
Output Open Circuit Protection
Over-Temperature Protection
Charge Pump Output Current Limit
LDO Current Limit
LED Float Detection
Output Open Circuit Protection
Over-Voltage Protection (OVP) is provided at the VOUT
pin to prevent the charge pump from producing an
excessively high output voltage. In the event of an open
circuit at VOUT, the charge pump runs in open loop and
the voltage rises up to the OVP limit. OVP operation is
hysteretic, meaning the charge pump will momentarily
turn off until VOUT is sufficiently reduced. The maximum
OVP threshold is 6.0V, allowing the use of a ceramic
output capacitor rated at 6.3V with no fear of over-voltage
damage.
Over-Temperature Protection
The Over-Temperature (OT) protection circuit helps
prevent the device from overheating and experiencing
a catastrophic failure. When the junction temperature
exceeds 160°C, the device goes into thermal shutdown
with all outputs disabled until the junction temperature
is reduced. All register information is retained during
thermal shutdown.
Charge Pump Output Current Limit
The device also limits the charge pump current at the
VOUT pin. When VOUT is shorted to ground, the typical
output current limit is 300mA. The current limiting is
triggered by an output under-voltage lockout below 2V.
The output returns to normal when the short is removed
and VOUT is above 2.5V. Above 2.5V, a typical current
limit of 300mA applies when the FL current sink is off and
a typical current limit of 1A applies when the FL current
sink is on.
LDO Current Limit
The device limits the output currents of LDO1 and LDO2 to
help prevent it from overheating and to protect the loads.
The minimum limit is 200mA, so load current greater than
the rated 100mA can be used with degraded accuracy
and larger dropout without tripping the current limit.
LED Float Detection
Float detect is a fault detection feature of the LED current
sink outputs. If an output is programmed to be enabled
and an open circuit fault occurs at any current sink output,
that output will be disabled to prevent a sustained output
OVP condition from occurring due to the resulting open
loop. Float detect ensures device protection but does
not ensure optimum performance. Unused LED outputs
must be disabled to prevent an open circuit fault from
occurring.
15
SC627
Applications Information (continued)
•
PCB Layout Considerations
The layout diagram in Figure 1 illustrates a proper
two-layer PCB layout for the SC627 and supporting
components. Following fundamental layout rules is
critical for achieving the performance specified in the
Electrical Characteristics table. The following guidelines
are recommended when developing a PCB layout:
GND
C1+
CLDO1
C2-
LDO1
PGND
LDO2
SC627
FL
Figure 2 — Layer 1
SWIF
CBYP
FLEN
NC
BL2
GREF
CLDO2
BYP
BL1
BL3
•
COUT
C2
C2+
C1-
C1
VOUT
CIN
•
VOUT
VIN
GND
AGND
•
VIN
•
Place all bypass and decoupling capacitors —
C1, C2, CIN, COUT, CLDO1, CLDO2, and CBYP as
close to the device as possible.
All charge pump current passes through VIN,
VOUT, and the bucket capacitor connection
pins. Ensure that all connections to these pins
make use of wide traces so that the resistive
drop on each connection is minimized.
The thermal pad should be connected to the
ground plane using multiple vias to ensure
proper thermal connection for optimal heat
transfer.
BL4
•
•
Make all ground connections to a solid
ground plane as shown in the example layout
(Figure 3).
If a ground layer is not feasible, the following
groupings should be connected:
ƒ PGND — CIN, COUT
ƒ AGND — Ground Pad, CLDO1, CLDO2,
CBYP
If no ground plane is available, PGND and
AGND should be routed back to the negative
battery terminal as separate signals using thick
traces. Joining the two ground returns at the
terminal prevents large pulsed return currents
from mixing with the low-noise return currents
of the LDOs.
Both LDO output traces should be made as
wide as possible to minimize resistive losses.
Figure 1 — Recommended PCB Layout
Figure 3 — Layer 2
16
SC627
Register Map
Address
D7
D6
D5
D4
D3
D2
D1
D0
Reset
Value
Description
0x00
FADE_1
FADE_0
FADE_EN
BL_4
BL_3
BL_2
BL_1
BL_0
0x00
Backlight
Current
Control
0x01
0(1)
0(1)
0(1)
0(1)
BLEN_4
BLEN_3
BLEN_2
BLEN_1
0x00
Backlight
Enable Control
0x02
0(1)
0(1)
0(1)
FLTO
FL_2
FL_1
FL_0
FL/SPLB
0x10
Flash/Spotlight
Control
0x03
0(1)
LDO2_2
LDO2_1
LDO2_0
LDO1_3
LDO1_2
LDO1_1
LDO1_0
0x00
LDO Control
Notes:
(1) 0 = always write a 0 to these bits
Register and Bit Definitions
Backlight Current Control Register (0x00)
This register is used to set the currents for the backlight
current sinks, as well as to enable and set the fade step
rate. These current sinks need to be enabled in the
Backlight Enable Control register to be active.
FADE[1:0]
These bits are used to set the rise/fall rate between two
backlight currents as follows:
FADE_1
FADE_0
Fade Feature
Rise/Fall Rate
(ms/step)
0
0
32
0
1
24
1
0
16
1
1
8
value to a new value set by bits BL[4:0] at a rate of 8ms to
32ms per step. A new backlight level cannot be written
during an ongoing fade operation, but an ongoing fade
operation may be cancelled by resetting the fade bit.
Clearing the fade bit during an ongoing fade operation
changes the backlight current immediately to the value
of BL[4:0]. The number of counts to complete a fade
operation equals the difference between the old and new
backlight values to increment or decrement the BL[4:0]
bits. If the fade bit is cleared, the current level will change
immediately without the fade delay. The rate of fade may
be changed dynamically, even while a fade operation is
active, by writing new values to the FADE_1 and FADE_0
bits. The total fade time is determined by the number of
steps between old and new backlight values, multiplied
by the rate of fade in ms/step. The longest elapsed time
for a full scale fade-out of the backlight is nominally 1.024
seconds when the default interval of 32ms is used.
The number of steps in changing the backlight current will
be equal to the change in binary count of bits BL[4:0].
FADE_EN
This bit is used to enable or disable the fade feature. When
the fade function is enabled and a new backlight current
is set, the backlight current will change from its current
17
SC627
Register and Bit Definitions (continued)
BL[4:0]
These bits are used to set the current for the backlight
current sinks. All enabled backlight current sinks will sink
the same current, as shown in Table 1.
Table 1 — Backlight Current Control Bits
BL_4 BL_3 BL_2 BL_1 BL_0
Backlight Current
(mA)
0
0
0
0
0
0.5
0
0
0
0
1
1.0
0
0
0
1
0
1.5
0
0
0
1
1
2.0
0
0
1
0
0
2.5
0
0
1
0
1
3.0
0
0
1
1
0
3.5
0
0
1
1
1
4.0
0
1
0
0
0
4.5
0
1
0
0
1
5
0
1
0
1
0
5.5
0
1
0
1
1
6
0
1
1
0
0
6.5
0
1
1
0
1
7
0
1
1
1
0
7.5
0
1
1
1
1
8
1
0
0
0
0
8.5
1
0
0
0
1
9
1
0
0
1
0
9.5
1
0
0
1
1
10
1
0
1
0
0
10.5
1
0
1
0
1
11
1
0
1
1
0
11.5
1
0
1
1
1
12
1
1
0
0
0
13
1
1
0
0
1
14
1
1
0
1
0
15
1
1
0
1
1
17
1
1
1
0
0
19
1
1
1
0
1
21
1
1
1
1
0
23
1
1
1
1
1
25
BL Enable Control Register (0x01)
This register is used to enable the backlight current
sinks.
BLEN[4:1]
These bits are used to enable current sinks (active high,
default low).
BLEN_4 — Enable bit for backlight BL4
BLEN_3 — Enable bit for backlight BL3
BLEN_2 — Enable bit for backlight BL2
BLEN_1 — Enable bit for backlight BL1
When enabled, the current sinks will carry the current set
by the backlight current control bits BL[4:0], as shown in
Table 1.
Flash/Spotlight Control Register (0x02)
This register is used to configure the flash time-out feature,
the flash or spotlight current, and select flash or spotlight
current ranges.
FLTO
This bit is used to enable the flash safety time-out feature.
The default state is enabled with FLTO = 1. If this bit is set,
the device will turn off the flash after a nominal period of
1s. Two ways to re-enable the flash function after a safety
time-out are:
Pull the FLEN pin low to re-enable the flash
function
Clear and re-write FL[2:0]
•
•
FL[2:0]
These bits are used to set the current for the flash current
sink when configured for flash or spotlight by the FL/SPLB
bit. Bits FL[2:0] set the flash or spotlight current, as shown
in Table 2.
18
SC627
Register and Bit Definitions (continued)
Table 2 — Flash/Spotlight Control Bits
FL_2
FL_1
FL_0
FL/
SPLB
Flash/Spotlight
Current (mA)
0
0
0
0
OFF
0
0
1
0
50
0
1
0
0
0
1
1
1
0
1
LDO2[2:0]
These bits are used to set the output voltage of LDO2, as
shown in Table 3.
Table 3 — LDO2 Control Bits
LDO2_2
LDO2_1
LDO2_0
LDO2
Output Voltage
100
0
0
0
OFF
0
150
0
0
1
1.8V
0
0
200
0
1
0
1.7V
0
1
0
250
0
1
1
1.6V
1
1
0
0
300(1)
1
0
0
1.5V
1
1
1
0
350(1)
0
0
0
1
OFF
0
0
1
1
400(1)
0
1
0
1
450(1)
LDO1[3:0]
These bits set the output voltage of LDO1, as shown in
Table 4.
0
1
1
1
500(1)
Table 4 — LDO1 Control Bits
1
0
0
1
550(1)
1
0
1
1
600(1)
1
1
0
1
650(1)
1
1
1
1
700(1)
Note:
(1) When on continuously, the device may reach the temperature
limit with 300mA and higher.
FL/SPLB
This bit is used to select either the flash or spotlight
current ranges. If this bit is set, the FL current sink can
be used to drive a flash of maximum duration 500ms and
the current range will be the high (flash) current range. If
this bit is cleared, the FL current sink can be used to drive
a continuous spotlight at a lower current and the current
range will be the lower (spotlight) current range, as shown
in Table 2.
LDO Control Register (0x03)
This register is used to enable the LDOs and to set their
output voltages.
101 through 111 are not used
OFF
LDO1_3
LDO1_2
LDO1_1
LDO1_0
LDO1
Output
Voltage
0
0
0
0
OFF
0
0
0
1
3.3V
0
0
1
0
3.2V
0
0
1
1
3.1V
0
1
0
0
3.0V
0
1
0
1
2.9V
0
1
1
0
2.8V
0
1
1
1
2.7V
1
0
0
0
2.6V
1
0
0
1
2.5V
1010 through 1111 are not used
OFF
19
SC627
SemWire Interface
Semwire Interface Functions
SemWire Communication Protocol and Timing
The SWIF pin is a write-only single wire interface. It
provides the capability to address up to 32 registers to
control device functionality. The protocol for using this
interface is described in the following subsections.
The following six step communication sequence controls
all device functions when the device is enabled.
Driving the SWIF Pin
The SWIF pin should be driven by a GPIO from the system
microcontroller. The output level can be configured as
either a push-pull driver (TTL or CMOS levels) or as an
open drain driver with an external pull-up resistor.
Enabling the Device
The SWIF pin must be pulled from low to high for a
period of greater than 1ms (tEN) to enable the device into
the sleep state. In the sleep state, the device bandgap is
active, UVLO monitoring is active, and the serial interface
is monitored for communication.
Automatic Sleep State
If both the backlight and flash current sinks are disabled,
the device automatically enters the sleep state in order
to minimize the current draw from the battery. When in
sleep mode, the charge pump and oscillator are both
disabled. The LDOs remain on if enabled.
Disabling the Device
The SWIF pin must be pulled from high to low for a
period greater than 10ms (tDIS) in order to shut down the
device. In this state the device remains disabled until the
SWIF pin is pulled high for a period greater than 1ms. All
registers return to the default state, resetting all bits to
zero except for FLT0, which defaults to one.
1. OSC On — The SWIF pin is toggled low for one bit
duration and high for one bit duration in order to
enable the oscillator. The oscillator is turned off in the
sleep state to minimize quiescent current.
2. Sample — The SWIF pin is toggled low for one bit
duration and high for one bit duration. During this
time, the device samples the bit rate and determines
the bit rate at which the register address and data
values that follow will arrive. The sample rate is at least
20 times the bit rate ensuring robust communication
synchronization.
3. Start — The SWIF pin is pulled low for one bit duration,
which starts communication with the target register.
4. Address — The next 5 bits are the address of the
target register — MSB first, LSB last.
5. Data — The next 8 bits are the data written to the
target register — MSB first, LSB last.
6. Standby — After the last data bit is sent, the SWIF pin
is pulled high for 5 bit durations to return the device
to standby before another data write can take place. If
all LEDs are disabled, the device will go back to sleep
mode.
NOTE: The bit rate must be set by the host controller to a
rate that is between the minimum and maximum
frequencies listed in the Electrical Characteristics section.
20
SC627
SemWire Interface (continued)
Single Write Operation
Device
Disabled
Device
Enabled
Into Sleep
OSC On
Sample
Register Address
Start A4
A3
A2
A1
5 Resume
high Sleep if
bits all LEDs
Min. are off
Data
A0
D7
D6
D5
D4
D3
D2
D1
t > tEN
Device
Disabled
when low
for tDIS
D0
t > DDL
t > tDIS
Concatenated Write Operation
OSC On
Sample
Register Address
Start
A4
A3
A2
A1
Data
A0
D7
D6
D5
D4
D3
OSC On
(Repeated)
D2
D1
D0
Sample
Start
t > DDL
To concatenate write operations, repeat Osc On, Sample
and Start after the DO bit of the previous sequence as
shown.
21
SC627
Outline Drawing — MLPQ-UT-20 3x3
A
D
PIN 1
INDICATOR
(LASER MARK)
DIMENSIONS
INCHES
MILLIMETERS
DIM
MIN NOM MAX MIN NOM MAX
B
E
A2
A
SEATING
PLANE
aaa C
A
A1
A2
b
D
D1
E
E1
e
L
N
aaa
bbb
.020
.000
-
.024
.002
(.006)
.006 .008 .010
.114 .118 .122
.061 .067 .071
.114 .118 .122
.061 .067 .071
.016 BSC
.012 .016 .020
20
.003
.004
0.50
0.00
-
0.60
0.05
(0.1524)
0.15 0.20 0.25
2.90 3.00 3.10
1.55 1.70 1.80
2.90 3.00 3.10
1.55 1.70 1.80
0.40 BSC
0.30 0.40 0.50
20
0.08
0.10
C
A1
D1
e
LxN
E/2
E1
2
1
N
D/2
bxN
bbb
C A B
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS .
3. DAP is 1.90 x 190mm.
22
SC627
Land Pattern — MLPQ-UT-20 3x3
H
R
(C)
DIMENSIONS
K
G
Y
X
P
Z
DIM
INCHES
MILLIMETERS
C
G
H
K
P
R
X
Y
Z
(.114)
(2.90)
.083
.067
.067
.016
.004
.008
.031
.146
2.10
1.70
1.70
0.40
0.10
0.20
0.80
3.70
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
3.
THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD
SHALL BE CONNECTED TO A SYSTEM GROUND PLANE.
FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR
FUNCTIONAL PERFORMANCE OF THE DEVICE.
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804
www.semtech.com
23