SEMTECH SC652

SC652
Backlight Driver for 5 LEDs with
Charge Pump and PWM Control
POWER MANAGEMENT
Features
Description
„
The SC652 is a high efficiency charge pump LED driver
using Semtech’s proprietary charge pump technology.
Performance is optimized for use in single-cell Li-ion
battery applications.
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Input supply voltage range — 2.9V to 5.5V
Charge pump modes — 1x, 1.5x and 2x
PWM dimming control with low pass filter provides
DC backlight current (not pulsed)
PWM frequency range — 200Hz to 50kHz
Five adjustable current sinks — 500μA to 25mA
Backlight current accuracy ±1.5% typical
Backlight current matching ±0.5% typical
LED float detection
Charge pump frequency — 250kHz
Low shutdown current — 0.1μA typical
Ultra-thin package — 2 x 2 x 0.6(mm)
Fully WEEE and RoHS compliant
The device provides backlight current using up to five
matched current sinks. The load and supply conditions
determine whether the charge pump operates in 1x, 1.5x,
or 2x mode.
The maximum current per LED is set by a resistor (RISET )
connected from the ISET pin to the input voltage. The
current can be set between 500μA and 25mA. This current
can be varied by applying a pulse-width modulated (PWM)
signal to the EN/PWM pin. A low-pass filter is used to
develop a DC current level rather than a pulsed current
output, resulting in a more efficient system. The resulting
DC current in each LED (IBL) is equal to the maximum
current setting multiplied by the duty cycle of the PWM
control signal. Using this control system, IBL can gradually
fade between levels.
Applications
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Cellular phones, smart phones, and PDAs
LCD display modules
Portable media players
Digital cameras
Personal navigation devices
Display/keypad backlighting and LED indicators
With a 2 x 2 (mm) package and 4 small capacitors, the
SC652 provides a complete LED driver solution with a
minimal PCB footprint.
Typical Application Circuit
SC652
VBAT = 2.9V to 5.5V
CIN
2.2μF
IN
PWM
Signal
OUT
COUT
2.2μF
EN/PWM
BL1
RISET
BL2
ISET
BL3
BL4
BL5
GND
C1+ C1C1
2.2μF
C2+ C2C2
2.2μF
US Patents: 6,504,422; 6,794,926
March 13, 2009
© 2009 Semtech Corporation
1
SC652
ISET
C1-
C2-
Evaluation Board
C1+
MLPQ-UT-14 2×2
13
12
11
SC652EVB
10
GND
2
9
BL1
3
8
BL2
TOP VIEW
5
EN/
PWM
4
6
7
BL3
IN
Package
14
BL4
1
Device
SC652ULTRT(1)(2)
BL5
OUT
Ordering Information
C2+
Pin Configuration
Notes:
(1) Available in tape and reel only. A reel contains 3,000 devices.
(2) Lead-free package only. Device is WEEE and RoHS compliant.
MLPQ-UT-14; 2x2, 14 LEAD
θJA = 127°C/W
Marking Information
AD
yw
AD = Marking code
yw = Date Code
2
SC652
Absolute Maximum Ratings
Recommended Operating Conditions
IN, OUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0
Ambient Temperature Range (°C) . . . . . . . . . . -40 ≤ TA ≤ +85
C1+, C2+ (V) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to (VOUT + 0.3)
Input Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 to 5.5
Pin Voltage — All Other Pins (V) . . . . . . . . . -0.3 to (VIN + 0.3)
Output Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 5.25
OUT Short Circuit Duration . . . . . . . . . . . . . . . . . Continuous
Voltage Difference between any two LEDs (V) . . . ΔVF ≤ 1.0(2)
ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Thermal Information
Thermal Resistance, Junction to Ambient(3) (°C/W) . . . 127
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) ΔVF(max) = 1.0V when VIN = 2.9V, higher VIN supports higher ΔVF(max)
(3) Calculated from package in still air, mounted to 3 x 4.5(in), 4 layer FR4 PCB per JESD51 standards.
Electrical Characteristics
Unless otherwise noted, TA = +25°C for Typ, -40°C to +85°C for Min and Max, TJ(MAX) = 125°C, VIN = 3.7V, CIN= COUT = C1= C2= 2.2μF, (ESR = 0.03Ω),
500μA < IFS_BL < 25mA, Duty Cycle of PWM = 100%, All 5 LEDs connected and enabled.
Parameter
Shutdown Current
Quiescent Current
Symbol
Conditions
IQ(OFF)
IQ
Min
Typ
Max
Units
TA = 25°C
0.1
2
μA
Charge pump in 1x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
1.5
Charge pump in 1.5x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
2
Charge pump in 2x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
2.5
mA
IOUT(MAX)
VIN > 3.0V, sum of all active LED currents,
VOUT(MAX) = 4.2V
125
Backlight Current Setting (1)
IFS_BL
PWM duty cycle = 100%, 200kΩ ≥ RISET ≥ 4kΩ
0.5
Current Gain
IGAIN
Gain from IISET to IFS_BL
100
A/A
VIN - ISET
Voltage across RISET
1
V
Backlight Current Matching (2)
IBL-BL
IFS_BL = 12mA, Duty = 100%
Backlight Current Accuracy
IBL_ACC
IFS_BL = 12mA, Duty = 100%
PWM Input Frequency
fEN/PWM
Guaranteed by design
Maximum Total Output Current
Current Set Voltage
EN/PWM Minimum High Time
tHIGH_MIN (3)
-3.5
mA
25
±0.5
+3.5
±1.5
0.2
%
%
50
1
mA
kHz
μs
3
SC652
Electrical Characteristics (continued)
Parameter
Symbol
Conditions
Current Transition Settling Time
ts
Duty cycle change from 100% to 50%(1)(4)
EN/PWM Low Time
tLT
Time that voltage on the EN/PWM pin can be low
without disabling the device
1x Mode to 1.5x Mode
Falling Transition Voltage
V TRANS1x
IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V
3.25
V
1.5x Mode to 1x Mode
Hysteresis
VHYST1x
IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V
300
mV
1.5x Mode to 2x Mode
Falling Transition Voltage
V TRANS1.5x
IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5)
2.9
V
2x Mode to 1.5x Mode Hysteresis
VHYST1.5x
IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5)
500
mV
Current Sink Off-State
Leakage Current
IBLn(off )
VIN = VBLn = 4.2V
0.1
Charge Pump Frequency
fPUMP
VIN = 3.2V
250
OUT pin shorted to GND
45
VOUT > 2.5V
400
Increasing VIN — lockout released
2.4
V
500
mV
Output Short Circuit Current Limit
Min
Typ
Max
0.5
s
5
VUVLO-OFF
UVLO Hysteresis
VUVLO-HYS
ms
1
μA
kHz
IOUT(SC)
Under Voltage Lockout Threshold
Units
mA
Over-Voltage Protection
VOVP
OUT pin open circuit, VOUT = VOVP — rising threshold
5.7
Over-Temperature
TOT
Rising Temperature
165
°C
25
°C
OT Hysteresis
TOT-HYS
6.0
V
Input High Threshold (6)
VIH
VIN = 5.5V
V
Input Low Threshold (6)
VIL
VIN = 2.9V
0.4
V
Input High Current (6)
IIH
VIN = 5.5V
1
μA
Input Low Current (6)
IIL
VIN = 5.5V
1
μA
1.4
Notes:
(1) Guaranteed by design
(2) Current matching equals ± [IBL(MAX) - IBL(MIN] / [IBL(MAX) + IBL(MIN)].
(3) tHIGH_MIN is the minimum time needed for accurate PWM sampling.
(4) The settling time is affected by the magnitude of change in the PWM duty cycle.
(5) Test voltage is VOUT = 4.0V — a relatively extreme LED voltage used to force a transition during test. Typically VOUT = 3.2V for white LEDs.
(6) Applied to EN/PWM pin.
4
SC652
Typical Characteristics
Backlight Accuracy (5 LEDs) — 25mA Each
8
6
6
4
4
Backlight Matching (%)
Backlight Accuracy (%)
8
Backlight Matching (5 LEDs) — 25mA Each
VOUT = 3.64V, IOUT = 125mA, 25°C
2
MAX LED
0
-2
MIN LED
-4
-6
VOUT = 3.64V, IOUT = 125mA, 25°C
2
0
-2
-4
-6
-8
4.2
3.9
3.6
3.3
3
-8
4.2
2.7
3.9
3.6
VIN(V)
Backlight Accuracy (5 LEDs) — 12mA Each
6
4
4
MAX LED
0
MIN LED
-2
-4
2
0
-2
-4
-8
4.2
3.9
3.6
VIN (V)
3.3
3
4.2
2.7
Backlight Accuracy (5 LEDs) — 0.5mA Each
VOUT = 3.09V, IOUT = 2.5mA, 25°C
8
6
6
4
4
MAX LED
2
0
-2
MIN LED
-4
-6
-8
4.2
3.9
3.6
VIN (V)
3.3
3
2.7
Backlight Matching (5 LEDs) — 0.5mA Each
Backlight Matching (%)
Backlight Accuracy (%)
8
2.7
-6
-6
-8
3
VOUT = 3.50V, IOUT = 60mA, 25°C
8
6
2
3.3
Backlight Matching (5 LEDs) — 12mA Each
VOUT = 3.50V, IOUT = 60mA, 25°C
Backlight Matching (%)
Backlight Accuracy (%)
8
VIN (V)
VOUT = 3.09V, IOUT = 2.5mA, 25°C
2
0
-2
-4
-6
-8
3.9
3.6
VIN (V)
3.3
3
2.7
4.2
3.9
3.6
VIN (V)
3.3
3
2.7
5
SC652
Typical Characteristics (continued)
Battery Current (5 LEDs) — 25mA Each
Backlight Efficiency (5 LEDs) — 25mA Each
VOUT = 3.64V, IOUT = 125mA, 25°C
100
200
180
Battery Current (mA)
Efficiency (%)
90
VOUT = 3.64V, IOUT = 125mA, 25°C
80
70
160
140
120
60
50
4.2
3.9
3.6
3.3
3
2.7
100
4.2
3.9
3.6
VIN (V)
VOUT = 3.50V, IOUT = 60mA, 25°C
100
Battery Current (mA)
Efficiency (%)
80
70
50
4.2
VOUT = 3.50V, IOUT = 60mA, 25°C
80
70
3.9
3.6
VIN(V)
3.3
3
50
4.2
2.7
Backlight Efficiency (5 LEDs) — 5.0mA Each
3.9
3.6
VIN (V)
3.3
3
2.7
Battery Current (5 LEDs) — 5.0mA Each
VOUT = 3.35V, IOUT = 25mA, 25°C
60
90
VOUT = 3.35V, IOUT = 25mA, 25°C
50
Battery Current (mA)
Efficiency (%)
2.7
60
60
80
70
60
50
3
90
90
100
3.3
Battery Current (5 LEDs) — 12mA Each
Backlight Efficiency (5 LEDs) — 12mA Each
100
VIN (V)
40
30
20
4.2
3.9
3.6
3.3
VIN (V)
3
2.7
10
4.2
3.9
3.6
VIN (V)
3.3
3
2.7
6
SC652
Typical Characteristics (continued)
Ripple — 1X Mode
Ripple — 1X Mode
VIN=4.2V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1)
VIN=4.2V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10μs/div)
Time (10μs/div)
Ripple — 1.5X Mode
Ripple — 1.5X Mode
VIN=3.2V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1)
VIN=3.2V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10μs/div)
Time (10μs/div)
Ripple — 2X Mode
Ripple — 2X Mode
VIN=2.9V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1)
VIN=2.9V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10μs/div)
Time (10μs/div)
NOTE 1: CIN = COUT = 4.7μF — 0603 size (1608 metric); C1 = C2 = 2.2μF — 0402 size (1005 metric)
NOTE 2: CIN = COUT= C1 = C2 = 2.2μF — 0603 size (1608 metric)
7
SC652
Typical Characteristics (continued)
PWM Accuracy — 4.2V
20
Percentage of Maximum IBL — 4.2V
VIN = 4.2V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
100
12
50kHz
8
200Hz
32kHz
4
80
Percentage of Maximum IBL (%)
Calculated IBL (mA)
16
60
4
8
12
Measured IBL (mA)
16
200Hz
40
20
0
0
VIN = 4.2V, RISET = 4.99kΩ
0
20
32kHz
0
Percentage of Maximum IBL (%)
Calculated IBL (mA)
16
12
50kHz
8
200Hz
32kHz
4
80
100
VIN = 3.7V, RISET = 4.99kΩ
80
60
200Hz
40
32kHz
50kHz
20
0
0
0
4
8
12
Measured IBL (mA)
16
0
20
VIN = 2.9V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
100
Percentage of Maximum IBL (%)
16
12
50kHz
8
200Hz
32kHz
4
20
40
60
PWM Duty Cycle (%)
80
100
Percentage of Maximum IBL — 2.9V
PWM Accuracy — 2.9V
Calculated IBL (mA)
40
60
PWM Duty Cycle (%)
VIN = 3.7V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
100
20
20
Percentage of Maximum IBL — 3.7V
PWM Accuracy — 3.7V
20
50kHz
VIN = 2.9V, RISET = 4.99kΩ
80
60
200Hz
40
32kHz
50kHz
20
0
0
0
4
12
8
Measured IBL (mA)
16
20
0
20
40
60
PWM Duty Cycle (%)
80
100
8
SC652
Typical Characteristics (continued)
Start-up — 0% to 50%
Start-up — 0% to 100%
VIN = 3.7V, 0 to 50% duty cycle, RISET = 4.99kΩ, fPWM = 32kHz
VIN = 3.7V, 0 to 100% duty cycle, RISET = 4.99kΩ, no PWM
20mA
10mA
IBL (10.0mA/div)
IBL (10.0mA/div)
0mA—
0mA—
VPWM (2V/div)
VPWM (2V/div)
0V—
50%
0V—
100%
Time (200ms/div)
Time (200ms/div)
IBL Settling Time — 100% to 50%
IBL Settling Time — 50% to 100%
VIN = 3.7V, RISET = 4.99kΩ, fPWM = 32kHz
VIN = 3.7V, RISET = 4.99kΩ, fPWM = 32kHz
20mA
IBL (10.0mA/div)
10mA
20mA
10mA
IBL (10.0mA/div)
0mA—
0mA—
VPWM (2V/div)
VPWM (2V/div)
0V— 50%
100%
0V—
100%
50%
Time (200ms/div)
Time (200ms/div)
DC Backlight Current — 32kHz PWM
DC Backlight Current — 200Hz PWM
VIN = 3.7V, 50% duty cycle, RISET = 4.99kΩ, IBL = 10mA
VIN = 3.7V, 50% duty cycle, RISET = 4.99kΩ, IBL = 10mA
IBL (10.0mA/div)
IBL (10.0mA/div)
0mA—
0mA—
VPWM (2V/div)
VPWM (2V/div)
0V—
0V—
Time (20μs/div)
Time (1ms/div)
9
SC652
Pin Descriptions
Pin #
Pin Name
Pin Function
1
OUT
2
IN
3
ISET
4
EN/PWM
5
BL5
Current sink output for main backlight LED 5 — leave this pin open if unused
6
BL4
Current sink output for main backlight LED 4 — leave this pin open if unused
7
BL3
Current sink output for main backlight LED 3 — leave this pin open if unused
8
BL2
Current sink output for main backlight LED 2 — leave this pin open if unused
9
BL1
Current sink output for main backlight LED 1 — leave this pin open if unused
10
GND
Ground pin
11
C2-
Negative connection to bucket capacitor 2
12
C1-
Negative connection to bucket capacitor 1
13
C1+
Positive connection to bucket capacitor 1
14
C2+
Positive connection to bucket capacitor 2
Charge pump output — all LED anode pins should be connected to this pin
Battery voltage input
Current setting pin — connect a resistor between this pin and the IN pin to set the LED current
Enable pin — also used as the PWM input for dimming control
10
SC652
Block Diagram
C1+ C1- C2+ C213
IN
2
EN/
PWM
4
ISET
3
VIN
Control
Interface
and Level
Converter
12
14
11
Fractional Charge Pump
(1x, 1.5x, 2x)
Oscillator
Current
Setting
Block
VOUT
1
OUT
9
BL1
8
BL2
7
BL3
6
BL4
5
BL5
GND 10
11
SC652
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
Five matched current sinks that control LED
backlighting current, providing 500μA to 25mA
per LED
EN/PWM pin functions as an enable and provides PWM control of the LED brightness
High Current Fractional Charge Pump
The backlight outputs are supported by a high efficiency,
high current fractional charge pump output. 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
mode as 1x, 1.5x, or 2x based on circuit conditions such
as LED voltage, input voltage, and load current. The 1x
mode is the most efficient of the three modes, followed
by 1.5x and 2x modes. 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 (1.5x or 2x) may be needed
momentarily to maintain regulation at the OUT pin
during intervals of high demand. The charge pump
responds to momentary high demands, setting the
charge pump to the optimum mode to deliver the output
voltage and load current while optimizing efficiency.
Hysteresis is provided to prevent mode toggling.
The charge pump requires two bucket capacitors for
proper operation. One capacitor must be connected
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
1μF to support the charge pump current requirements.
The device also requires at least 1μF capacitance on the IN
pin and at least 1μF capacitance on the OUT pin to mini-
mize noise and support the output drive requirements of
IOUT up to 90mA. For output currents higher than 90mA, a
nominal value of 4.7μF is recommended for COUT and CIN.
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.
It is important that the minimum value of the capacitors
used is no lower than 1μF. This may require the use of
2.2μF capacitors to be sure that the degradation of
capacitance due to DC voltage does not cause the
capacitance to go below 1μF.
LED Backlight Current Sinks
The full scale backlight current (I FS_BL) is set via the
current through the ISET pin (IISET ). IFS_BL is regulated to
the value of IISET multiplied by an internal gain of 100A/A.
RISET is used to control the current through the ISET pin.
The relationship between RISET and the full scale backlight current is:
RISET = 100/IFS_BL
All backlight current sinks have matched currents, even
when there is a variation in the forward voltages (ΔVF )
of the LEDs. A ΔVF of 1.0V is supported when the input
voltage is at 2.9V. Higher ΔVF LED mis-match is supported when VIN is higher than 2.9V. All current sink
outputs are compared and the lowest output is used for
setting the voltage regulation at the OUT pin. This is
done to ensure that sufficient bias exists for all LEDs.
Any unused outputs must be left open and unused LED
drivers will remain disabled.
PWM Operation
A PWM signal can be used to adjust the DC current
through the LEDs. When the duty cycle is 100%, the
backlight current through each LED (IBL) equals the full
scale current set by RISET. As the duty cycle decreases, the
EN/PWM input samples the control signal and converts
the duty cycle to a DC current level. In conventional
PWM controlled systems, the output current pulses on
and off with the PWM input to achieve an effective
12
SC652
Applications Information (continued)
average current. Providing a DC current through the
LEDs instead of a pulsed current provides an efficiency
advantage over other PWM controlled systems by allowing the charge pump to remain in 1x mode longer
because the maximum current is equal to the average
current.
PWM Sampling
The sampling system that translates the PWM signal to
a DC current requires the EN/PWM pin to have a
minimum high time tHIGH_MIN to set the DC level. High
time less than tHIGH_MIN impacts the accuracy of the target
I BL. The minimum duty cycle needed to support the
minimum high time specification varies with the applied
PWM frequency (see figure 1). Note that use of a lower
PWM frequency, from 200Hz to 10kHz, will support
lower minimum duty cycle and an extended backlight
dimming range.
tHIGH_MIN = 1μs
5
Minimum Duty Cycle (%)
4
3
2
1
0
0
10
20
30
40
50
PWM Frequency (kHz)
Figure 1 — Minimum Duty Cycle
Shutdown Mode
The device is disabled when the EN/PWM pin is held low
for 7ms or longer.
Protection Features
•
•
Charge Pump Output Current Limit
LED Float Detection
Output Open Circuit Protection
Over-Voltage Protection (OVP) at the OUT pin prevents
the charge pump from producing an excessively high
output voltage. In the event of an open circuit between
the OUT pin and all current sinks (no loads connected),
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.
Over-Temperature Protection
The Over-Temperature (OT) protection circuit prevents
the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds
165°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. Hysteresis of 20°C is provided to
ensure that the device cools sufficiently before
re-enabling.
Charge Pump Output Current Limit
The device limits the charge pump current at the OUT
pin. If the OUT pin is shorted to ground, or VOUT is lower
than 2.5V, the typical output current limit is 45mA. The
typical output current is limited to 400mA when over
loaded resistively with VOUT greater than 2.5V.
LED Float Detection
Float detect is a fault detection feature of the LED backlight outputs. If an output is programmed to be enabled
and an open circuit fault occurs at any backlight 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.
The SC652 provides several protection features to safeguard the device from catastrophic failures. These features
include:
•
•
Output Open Circuit Protection
Over-Temperature Protection
13
SC652
Applications Information (continued)
PCB Layout Considerations
The layout diagram in Figure 2 illustrates a proper two
layer PCB layout for the SC652 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:
•
•
•
•
•
Place all bucket and decoupling capacitors —
C1, C2, CIN, and COUT — as close to the device as
possible.
All charge pump current passes through pins
IN, OUT, C1+, C2+, C1-, and C2-. Therefore,
ensure that all connections to these pins make
use of wide traces so that the voltage drop on
each connection is minimized.
The GND pin should be connected to a ground
plane using multiple vias to ensure proper
thermal connection for optimal heat transfer.
Make solid ground connections between the
grounds of the COUT, CIN, and the GND pin on the
device.
Resistor RSET should be connected as shown in
Figure 2, close to pins IN and ISET. The placement and routing shown minimizes parasitic
capacitance at the ISET pin.
•
Figure 4 shows layer 2, and has only two net
connections, GND and OUT. Note that OUT is
routed around the GND pin, and does not
interfere with the ground connections between
CIN, COUT and the GND pin. Also, layer 2 has a
blank void in the copper beneath the ISET
trace. The blank space reduces the capacitance
coupled to the ISET pin.
Figure 3 — Layer 1
Ground Plane
C2
C1
OUT
GND
SC652
IN
CIN
BL1
ISET
RSET
BL3
BL4
BL5
BL2
EN/
PWM
IN
GND
C2-
C1-
COUT
C1+
C2+
GND
OUT
Figure 4 — Layer 2
Figure 2 — Recommended PCB Layout
•
Figure 3 shows the pads on layer 1 that should
be connected with vias to layer 2. CIN, COUT and
the GND pin all use vias to connect to the
ground plane. The OUT pin also uses vias and
routes on layer 2.
14
SC652
Outline Drawing — MLPQ-UT-14 2x2
B
D
A
DIMENSIONS
DIM
PIN 1
INDICATOR
(LASER MARK)
A
A1
A2
b
D
E
e
E
L
L1
N
aaa
bbb
A2
A
aaa
INCHES
MIN
.020
.000
.006
.077
.077
.010
.014
NOM
(.006)
.008
.079
.079
.016 BSC
.012
.016
14
.003
.004
MILLIMETERS
MAX
.024
.002
.010
.081
.081
.014
.018
MIN
0.50
0.00
NOM
-
(0.152)
0.20
2.00
2.00
0.40 BSC
0.25
0.30
0.35
0.40
14
0.08
0.10
0.15
1.95
1.95
MAX
0.60
0.05
0.25
2.05
2.05
0.35
0.45
SEATING
PLANE
C
C
A1
LxN
bxN
bbb
e/2
C A
B
E/2
e
0.20
0.15
1
N
L1
D/2
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
15
SC652
Land Pattern — MLPQ-UT-14 2x2
R
X
DIMENSIONS
DIM
(C)
Z
G
INCHES
MILLIMETERS
C
(.079)
(2.00)
G
.055
1.40
P
.016
0.40
R
.004
0.10
X
.008
0.20
Y
.024
0.60
Z
.102
2.60
P
Y
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. SQUARE PACKAGE - DIMENSIONS APPLY IN BOTH " X " AND " Y " DIRECTIONS.
4. PIN 1 PAD CAN BE SHORTER THAN THE ACTUAL PACKAGE LEAD TO AVOID
SOLDER BRIDGING BETWEEN PINS 1 & 14.
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
16