SC652ULTRT [SEMTECH]
Backlight Driver for 5 LEDs with Charge Pump and PWM Control; 背光驱动器的5个LED电荷泵和PWM控制
| 型号： | SC652ULTRT |
| 厂家： | 
SEMTECH CORPORATION |
| 描述： | Backlight Driver for 5 LEDs with Charge Pump and PWM Control |
| 文件： | 总16页 (文件大小：282K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SC652
Backlight Driver for 5 LEDs with
Charge Pump and PWM Control
POWER MANAGEMENT
Features
Description
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)
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.
PWM frequency range — 200Hz to 50kHz
Five adjustable current sinks — 500μA to 25mA
Backlight current accuracy 1.5ꢀ typical
Backlight current matching 0.5ꢀ 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
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
IN
OUT
COUT
2.2μF
PWM
Signal
EN/PWM
CIN
2.2μF
BL1
BL2
BL3
BL4
BL5
RISET
ISET
GND
C1+ C1- C2+ C2-
C1
2.2μF
C2
2.2μF
US Patents: 6,504,422; 6,794,926
1
March 13, 2009
© 2009 Semtech Corporation
SC652
Pin Configuration
Ordering Information
Device
Package
SC652ULTRT(1)(2)
MLPQ-UT-14 2×2
Evaluation Board
SC652EVB
Notes:
14
13
12
11
(1) Available in tape and reel only. A reel contains 3,000 devices.
(2) Lead-free package only. Device is WEEE and RoHS compliant.
TOP VIEW
10
9
OUT
IN
GND
BL1
BL2
1
2
3
ISET
8
7
4
5
6
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
C1+, C2+ (V) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to (VOUT + 0.3)
Pin Voltage — All Other Pins (V) . . . . . . . . . -0.3 to (VIN + 0.3)
OUT Short Circuit Duration . . . . . . . . . . . . . . . . . Continuous
ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Ambient Temperature Range (°C). . . . . . . . . . -40 ≤TA ≤ +85
Input Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 to 5.5
Output Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 5.25
VoltageDifferencebetweenanytwoLEDs(V)... ΔVF ≤1.0(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 = 100ꢀ, All 5 LEDs connected and enabled.
Parameter
Symbol
Conditions
Min
Typ
Max
Units
Shutdown Current
IQ(OFF)
TA = 25°C
0.1
2
μA
Charge pump in 1x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
1.5
2
Charge pump in 1.5x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
Quiescent Current
IQ
mA
Charge pump in 2x mode, 2.9V < VIN < 4.2V, 5 LEDs
enabled
2.5
VIN > 3.0V, sum of all active LED currents,
Maximum Total Output Current
IOUT(MAX)
125
0.5
mA
V
OUT(MAX) = 4.2V
Backlight Current Setting (1)
Current Gain
IFS_BL
IGAIN
VIN - ISET
IBL-BL
IBL_ACC
fEN/PWM
PWM duty cycle = 100ꢀ, 200kΩ ≥ RISET ≥ 4kΩ
Gain from IISET to IFS_BL
25
mA
A/A
V
100
1
Current Set Voltage
Voltage across RISET
Backlight Current Matching (2)
Backlight Current Accuracy
PWM Input Frequency
EN/PWM Minimum High Time
IFS_BL = 12mA, Duty = 100ꢀ
IFS_BL = 12mA, Duty = 100ꢀ
Guaranteed by design
-3.5
0.2
0.5
1.5
+3.5
50
ꢀ
ꢀ
kHz
μs
(3)
tHIGH_MIN
1
3
SC652
Electrical Characteristics (continued)
Parameter
Symbol
Conditions
Min
Typ
Max
Units
Current Transition Settling Time
ts
Duty cycle change from 100ꢀ to 50ꢀ(1)(4)
0.5
s
Time that voltage on the EN/PWM pin can be low
without disabling the device
EN/PWM Low Time
tLT
5
ms
V
1x Mode to 1.5x Mode
Falling Transition Voltage
VTRANS1x
IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V
IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V
3.25
300
1.5x Mode to 1x Mode
Hysteresis
VHYST1x
mV
1.5x Mode to 2x Mode
Falling Transition Voltage
VTRANS1.5x
VHYST1.5x
IBLn(off)
IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5)
IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5)
VIN = VBLn = 4.2V
2.9
500
0.1
V
2x Mode to 1.5x Mode Hysteresis
mV
μA
Current Sink Off-State
Leakage Current
1
Charge Pump Frequency
fPUMP
VIN = 3.2V
OUT pin shorted to GND
VOUT > 2.5V
250
45
kHz
Output Short Circuit Current Limit
IOUT(SC)
mA
400
2.4
500
5.7
165
25
Under Voltage Lockout Threshold
UVLO Hysteresis
VUVLO-OFF
VUVLO-HYS
VOVP
TOT
Increasing VIN — lockout released
V
mV
V
Over-Voltage Protection
Over-Temperature
OUT pin open circuit, VOUT = VOVP — rising threshold
Rising Temperature
6.0
°C
°C
V
OT Hysteresis
TOT-HYS
VIH
Input High Threshold (6)
Input Low Threshold (6)
Input High Current (6)
Input Low Current (6)
VIN = 5.5V
VIN = 2.9V
VIN = 5.5V
VIN = 5.5V
1.4
VIL
0.4
1
V
IIH
μA
μA
IIL
1
Notes:
(1) Guaranteed by design
(2) Current matching equals ꢁIBL(MAX) - IBL(MIN] / ꢁIBL(MAX) + IBL(MIN)].
(3) HIGH_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.
t
(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
OUT = 3.64V, IOUT = 125mA, 25°C
Backlight Matching (5 LEDs) — 25mA Each
VOUT = 3.64V, IOUT = 125mA, 25°C
V
8
6
8
6
4
4
2
2
MAX LED
MIN LED
0
0
-2
-4
-6
-8
-2
-4
-6
-8
4.2
3.9
3.6
3.3
3
2.7
4.2
3.6
3.3
3
2.7
3.9
VIN (V)
VIN(V)
Backlight Accuracy (5 LEDs) — 12mA Each
VOUT = 3.50V, IOUT = 60mA, 25°C
Backlight Matching (5 LEDs) — 12mA Each
VOUT = 3.50V, IOUT = 60mA, 25°C
8
6
8
6
4
4
2
2
MAX LED
MIN LED
0
0
-2
-2
-4
-6
-8
-4
-6
-8
4.2
3.9
3.3
3
2.7
4.2
2.7
3.6
3.9
3.6
3.3
3
V
IN (V)
VIN (V)
Backlight Accuracy (5 LEDs) — 0.5mA Each
Backlight Matching (5 LEDs) — 0.5mA Each
VOUT = 3.09V, IOUT = 2.5mA, 25°C
VOUT = 3.09V, IOUT = 2.5mA, 25°C
8
6
8
6
4
4
MAX LED
MIN LED
2
2
0
0
-2
-4
-6
-8
-2
-4
-6
-8
3
2.7
4.2
3.9
3.6
3.3
3
2.7
4.2
3.9
3.6
3.3
V
IN (V)
VIN (V)
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
VOUT = 3.64V, IOUT = 125mA, 25°C
200
180
160
140
90
80
70
60
50
120
100
4.2
2.7
4.2
3
3.9
3.6
3.3
3.9
3.6
3.3
3
2.7
VIN (V)
VIN (V)
Battery Current (5 LEDs) — 12mA Each
VOUT = 3.50V, IOUT = 60mA, 25°C
Backlight Efficiency (5 LEDs) — 12mA Each
VOUT = 3.50V, IOUT = 60mA, 25°C
100
90
100
90
80
70
60
50
80
70
60
50
4.2
2.7
4.2
3.9
3.6
3.3
3
3.9
3.6
3.3
3
2.7
VIN (V)
V
IN(V)
Backlight Efficiency (5 LEDs) — 5.0mA Each
Battery Current (5 LEDs) — 5.0mA Each
VOUT = 3.35V, IOUT = 25mA, 25°C
VOUT = 3.35V, IOUT = 25mA, 25°C
100
90
60
50
40
30
20
10
80
70
60
50
4.2
3.9
3.6
3.3
3
2.7
4.2
3.6
3.9
3.3
3
2.7
VIN (V)
VIN (V)
6
SC652
Typical Characteristics (continued)
Ripple — 1X Mode
Ripple — 1X Mode
VIN=4.2V, RISET = 5.56kΩ, 5 Backlights — 18 mA each, 25°C (see note 2)
VIN=4.2V, RISET = 4kΩ, 5 Backlights — 25 mA each, 25°C (see note 1)
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)
V
OUT (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)
V
OUT (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
VIN = 4.2V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
Percentage of Maximum IBL — 4.2V
VIN = 4.2V, RISET = 4.99kΩ
100
80
60
40
20
0
20
16
12
200Hz
32kHz
50kHz
8
4
0
50kHz
200Hz
32kHz
0
4
8
12
16
20
0
20
40
60
80
100
Measured IBL (mA)
PWM Duty Cycle (%)
Percentage of Maximum IBL — 3.7V
PWM Accuracy — 3.7V
V
IN = 3.7V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
20
16
12
8
VIN = 3.7V, RISET = 4.99kΩ
100
80
60
40
200Hz
50kHz
200Hz
32kHz
32kHz
50kHz
4
20
0
0
0
20
40
60
80
100
0
4
8
12
16
20
Measured IBL (mA)
PWM Duty Cycle (%)
Percentage of Maximum IBL — 2.9V
VIN = 2.9V, RISET = 4.99kΩ
PWM Accuracy — 2.9V
VIN = 2.9V, RISET = 4.99kΩ, Calculated IBL = (100/RISET) x Duty Cycle
100
80
60
40
20
0
20
16
12
8
200Hz
32kHz
50kHz
200Hz
50kHz
32kHz
4
0
0
20
40
60
80
100
0
4
8
12
16
20
Measured IBL (mA)
PWM Duty Cycle (%)
8
SC652
Typical Characteristics (continued)
Start-up — 0% to 50%
Start-up — 0% to 100%
VIN = 3.7V, 0 to 50ꢀ duty cycle, RISET = 4.99kΩ, fPWM = 32kHz
VIN = 3.7V, 0 to 100ꢀ duty cycle, RISET = 4.99kΩ, no PWM
20mA
10mA
IBL (10.0mA/div)
IBL (10.0mA/div)
0mA—
0mA—
V
PWM (2V/div)
V
PWM (2V/div)
0V—
0V—
100ꢀ
50ꢀ
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
20mA
10mA
10mA
IBL (10.0mA/div)
0mA—
IBL (10.0mA/div)
0mA—
V
PWM (2V/div)
0V—
V
PWM (2V/div)
0V—
50ꢀ
100ꢀ
50ꢀ
100ꢀ
Time (200ms/div)
Time (200ms/div)
DC Backlight Current — 32kHz PWM
DC Backlight Current — 200Hz PWM
VIN = 3.7V, 50ꢀ duty cycle, RISET = 4.99kΩ, IBL = 10mA
VIN = 3.7V, 50ꢀ duty cycle, RISET = 4.99kΩ, IBL = 10mA
IBL (10.0mA/div)
0mA—
IBL (10.0mA/div)
0mA—
V
PWM (2V/div)
0V—
V
PWM (2V/div)
0V—
Time (1ms/div)
Time (20ꢀs/div)
9
SC652
Pin Descriptions
Pin #
Pin Name
OUT
IN
Pin Function
1
2
Charge pump output — all LED anode pins should be connected to this pin
Battery voltage input
3
ISET
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
Current sink output for main backlight LED 5 — leave this pin open if unused
Current sink output for main backlight LED 4 — leave this pin open if unused
Current sink output for main backlight LED 3 — leave this pin open if unused
Current sink output for main backlight LED 2 — leave this pin open if unused
Current sink output for main backlight LED 1 — leave this pin open if unused
Ground pin
4
EN/PWM
BL5
5
6
BL4
7
BL3
8
BL2
9
BL1
10
11
12
13
14
GND
C2-
Negative connection to bucket capacitor 2
C1-
Negative connection to bucket capacitor 1
C1+
Positive connection to bucket capacitor 1
C2+
Positive connection to bucket capacitor 2
10
SC652
Block Diagram
C1+ C1- C2+ C2-
13 12 14 11
VIN
VOUT
Fractional Charge Pump
(1x, 1.5x, 2x)
IN 2
1
OUT
EN/
4
Oscillator
Control
Interface
and Level
Converter
9
8
7
6
5
BL1
PWM
BL2
BL3
BL4
BL5
Current
Setting
Block
3
ISET
GND 10
11
SC652
Applications Information
mize noise and support the output drive requirements of
General Description
IOUT up to 90mA. For output currents higher than 90mA, a
This design is optimized for handheld applications sup-
plied from a single Li-Ion cell and includes the following
key features:
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.
• 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
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.
• EN/PWM pin functions as an enable and pro-
vides 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.
LED Backlight Current Sinks
The full scale backlight current (IFS_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.
R
ISET is used to control the current through the ISET pin.
The relationship between RISET and the full scale back-
light current is:
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.
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 sup-
ported 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.
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 con-
nected 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-
PWM Operation
A PWM signal can be used to adjust the DC current
through the LEDs. When the duty cycle is 100ꢀ, 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 allow-
ing the charge pump to remain in 1x mode longer
because the maximum current is equal to the average
current.
• 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.
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
IBL. 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.
Over-Temperature Protection
The Over-Temperature (OT) protection circuit prevents
the device from overheating and experiencing a cata-
strophic 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.
tHIGH_MIN = 1μs
5
4
3
2
1
0
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.
0
10
20
PWM Frequency (kHz)
40
50
30
LED Float Detection
Figure 1 — Minimum Duty Cycle
Shutdown Mode
The device is disabled when the EN/PWM pin is held low
for 7ms or longer.
Float detect is a fault detection feature of the LED back-
light 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 result-
ing open loop. Float detect ensures device protection
but does not ensure optimum performance.
Protection Features
The SC652 provides several protection features to safe-
guard 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 compo-
nents. Following fundamental layout rules is critical for
achieving the performance specified in the Electrical
Characteristics table. The following guidelines are rec-
ommended when developing a PCB layout:
• 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.
• 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 place-
ment and routing shown minimizes parasitic
capacitance at the ISET pin.
Figure 3 — Layer 1
Ground Plane
C2
C1
GND
GND
COUT
OUT
IN
GND
BL1
BL2
SC652
CIN
ISET
RSET
IN
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
A
D
DIMENSIONS
INCHES
MIN NOM MAX MIN NOM MAX
MILLIMETERS
DIM
-
-
A
A1
A2
b
.020
.000
0.50
0.00
0.60
0.05
.024
.002
-
-
PIN 1
INDICATOR
(LASER MARK)
(.006)
.008
(0.152)
0.20
E
.006
.010
.081
.081
0.15
1.95
1.95
0.25
2.05
2.05
D
.079
2.00
.077
.077
E
.079
2.00
e
.016 BSC
.012
0.40 BSC
0.30
L
L1
N
.010
.014
.014
.018
0.25
0.35
0.35
0.45
.016
0.40
14
14
aaa
.003
.004
0.08
bbb
0.10
A2
C
A
SEATING
PLANE
aaa
C
A1
LxN
e/2
bxN
bbb
C
A
B
E/2
e
0.15
1
0.20
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
INCHES
DIM
MILLIMETERS
(.079)
.055
.016
.004
.008
.024
.102
(2.00)
1.40
0.40
0.10
0.20
0.60
2.60
C
G
P
R
X
Y
Z
Z
(C)
G
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
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