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SC652
Backlight Driver for 5 LEDs with Charge Pump and PWM Control
POWER MANAGEMENT Features
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 -- 500A to 25mA Backlight current accuracy 1.5% typical Backlight current matching 0.5% typical LED float detection Charge pump frequency -- 250kHz Low shutdown current -- 0.1A typical Ultra-thin package -- 2 x 2 x 0.6(mm) Fully WEEE and RoHS compliant
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. 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 500A 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. With a 2 x 2 (mm) package and 4 small capacitors, the SC652 provides a complete LED driver solution with a minimal PCB footprint.
Applications
Cellular phones, smart phones, and PDAs LCD display modules Portable media players Digital cameras Personal navigation devices Display/keypad backlighting and LED indicators
Typical Application Circuit
VBAT = 2.9V to 5.5V CIN 2.2F PWM Signal
SC652
IN EN/PWM OUT COUT 2.2F BL1 RISET ISET BL2 BL3 BL4 GND C1+ C1C1 2.2F BL5 C2+ C2C2 2.2F
US Patents: 6,504,422; 6,794,926 March 13, 2009 (c) 2009 Semtech Corporation 1
SC652
Pin Configuration
C2+ C1+ C1C2-
Ordering Information
Device
SC652ULTRT(1)(2) SC652EVB
Package
MLPQ-UT-14 2x2 Evaluation Board
14
13
12
11
OUT IN ISET
1 2 3
TOP VIEW
10
GND BL1 BL2
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.
9
8
4
5
6
7
EN/ PWM
BL5
BL4
MLPQ-UT-14; 2x2, 14 LEAD JA = 127C/W
Marking Information
AD yw
AD = Marking code yw = Date Code
BL3
2
SC652
Absolute Maximum Ratings
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
Recommended Operating Conditions
Ambient Temperature Range (C) . . . . . . . . . . -40 TA +85 Input Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 to 5.5 Output Voltage (V) . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 5.25 Voltage Difference between any two LEDs (V) . . . VF 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) VF(max) = 1.0V when VIN = 2.9V, higher VIN supports higher VF(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 = +25C for Typ, -40C to +85C for Min and Max, TJ(MAX) = 125C, VIN = 3.7V, CIN= COUT = C1= C2= 2.2F, (ESR = 0.03), 500A < IFS_BL < 25mA, Duty Cycle of PWM = 100%, All 5 LEDs connected and enabled.
Parameter
Shutdown Current
Symbol
IQ(OFF)
Conditions
TA = 25C Charge pump in 1x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled
Min
Typ
0.1 1.5
Max
2
Units
A
Quiescent Current
IQ
Charge pump in 1.5x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled Charge pump in 2x mode, 2.9V < VIN < 4.2V, 5 LEDs enabled
2
mA
2.5
Maximum Total Output Current Backlight Current Setting (1) Current Gain Current Set Voltage Backlight Current Matching (2) Backlight Current Accuracy PWM Input Frequency EN/PWM Minimum High Time
IOUT(MAX) IFS_BL IGAIN VIN - ISET IBL-BL IBL_ACC fEN/PWM tHIGH_MIN (3)
VIN > 3.0V, sum of all active LED currents, VOUT(MAX) = 4.2V PWM duty cycle = 100%, 200k RISET 4k Gain from IISET to IFS_BL Voltage across RISET IFS_BL = 12mA, Duty = 100% IFS_BL = 12mA, Duty = 100% Guaranteed by design
125 0.5 100 1 -3.5 0.5 1.5 0.2 1 50 +3.5 25
mA mA A/A V % % kHz s
3
SC652
Electrical Characteristics (continued)
Parameter
Current Transition Settling Time EN/PWM Low Time 1x Mode to 1.5x Mode Falling Transition Voltage 1.5x Mode to 1x Mode Hysteresis 1.5x Mode to 2x Mode Falling Transition Voltage 2x Mode to 1.5x Mode Hysteresis Current Sink Off-State Leakage Current Charge Pump Frequency
Symbol
ts tLT V TRANS1x VHYST1x V TRANS1.5x VHYST1.5x IBLn(off ) fPUMP IOUT(SC)
Conditions
Duty cycle change from 100% to 50%(1)(4) Time that voltage on the EN/PWM pin can be low without disabling the device IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V IOUT = 50mA, IBLn = 10mA, VOUT = 3.2V IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5) IOUT = 50mA, IBLn = 10mA, VOUT = 4.0V(5) VIN = VBLn = 4.2V VIN = 3.2V OUT pin shorted to GND
Min
Typ
0.5
Max
Units
s
5
ms
3.25
V
300
mV
2.9 500 0.1 250 45 1
V mV A kHz
Output Short Circuit Current Limit
mA VOUT > 2.5V 400 2.4 500 OUT pin open circuit, VOUT = VOVP -- rising threshold Rising Temperature 5.7 165 25 VIN = 5.5V VIN = 2.9V VIN = 5.5V VIN = 5.5V 1.4 0.4 1 1 6.0 V mV V C C V V A A
Under Voltage Lockout Threshold UVLO Hysteresis Over-Voltage Protection Over-Temperature OT Hysteresis Input High Threshold (6) Input Low Threshold (6) Input High Current (6) Input Low Current (6)
VUVLO-OFF VUVLO-HYS VOVP TOT TOT-HYS VIH VIL IIH IIL
Increasing VIN -- lockout released
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 VOUT = 3.64V, IOUT = 125mA, 25C
8 6 4 2 0 -2 -4 -6 -8 4.2
Backlight Matching (5 LEDs) -- 25mA Each
VOUT = 3.64V, IOUT = 125mA, 25C
Backlight Accuracy (%)
2 0 -2 MIN LED -4 -6 -8 4.2 MAX LED
Backlight Matching (%)
4
3.9
3.6 VIN(V)
3.3
3
2.7
3.9
3.6
VIN (V)
3.3
3
2.7
Backlight Accuracy (5 LEDs) -- 12mA Each
8 6 4 2 0 -2 -4 -6 -8 MIN LED VOUT = 3.50V, IOUT = 60mA, 25C
Backlight Matching (5 LEDs) -- 12mA Each
8 6 4 2 0 -2 -4 -6 -8 VOUT = 3.50V, IOUT = 60mA, 25C
Backlight Accuracy (%)
MAX LED
Backlight Matching (%)
4.2
3.9
3.6
VIN (V)
3.3
3
2.7
4.2
3.9
3.6
VIN (V)
3.3
3
2.7
Backlight Accuracy (5 LEDs) -- 0.5mA Each
8 6 4 2 0 -2 -4 -6 -8 4.2 MAX LED VOUT = 3.09V, IOUT = 2.5mA, 25C
Backlight Matching (5 LEDs) -- 0.5mA Each
8 6 4 2 0 -2 -4 -6 -8 VOUT = 3.09V, IOUT = 2.5mA, 25C
Backlight Accuracy (%)
MIN LED
Backlight Matching (%)
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)
Backlight Efficiency (5 LEDs) -- 25mA Each
100 VOUT = 3.64V, IOUT = 125mA, 25C 200
Battery Current (5 LEDs) -- 25mA Each
VOUT = 3.64V, IOUT = 125mA, 25C
90
Battery Current (mA)
180
Efficiency (%)
80
160
70
140
60
120
50 4.2
3.9
3.6 VIN (V)
3.3
3
2.7
100 4.2
3.9
3.6
VIN (V)
3.3
3
2.7
Backlight Efficiency (5 LEDs) -- 12mA Each
100 VOUT = 3.50V, IOUT = 60mA, 25C
Battery Current (5 LEDs) -- 12mA Each
100 VOUT = 3.50V, IOUT = 60mA, 25C
90
90
Battery Current (mA)
Efficiency (%)
80
80
70
70
60
60
50 4.2
3.9
3.6
VIN(V)
3.3
3
2.7
50 4.2
3.9
3.6
VIN (V)
3.3
3
2.7
Backlight Efficiency (5 LEDs) -- 5.0mA Each
100 VOUT = 3.35V, IOUT = 25mA, 25C
Battery Current (5 LEDs) -- 5.0mA Each
60 VOUT = 3.35V, IOUT = 25mA, 25C
90
50
80
Battery Current (mA)
4.2 3.9 3.6 VIN (V) 3.3 3 2.7
Efficiency (%)
40
70
30
60
20
50
10 4.2
3.9
3.6
VIN (V)
3.3
3
2.7
6
SC652
Typical Characteristics (continued)
Ripple -- 1X Mode
VIN=4.2V, RISET = 4k, 5 Backlights -- 25 mA each, 25C (see note 1)
Ripple -- 1X Mode
VIN=4.2V, RISET = 5.56k, 5 Backlights -- 18 mA each, 25C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10s/div)
Time (10s/div)
Ripple -- 1.5X Mode
VIN=3.2V, RISET = 4k, 5 Backlights -- 25 mA each, 25C (see note 1)
Ripple -- 1.5X Mode
VIN=3.2V, RISET = 5.56k, 5 Backlights -- 18 mA each, 25C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10s/div)
Time (10s/div)
Ripple -- 2X Mode
VIN=2.9V, RISET = 4k, 5 Backlights -- 25 mA each, 25C (see note 1)
Ripple -- 2X Mode
VIN=2.9V, RISET = 5.56k, 5 Backlights -- 18 mA each, 25C (see note 2)
VIN (100mV/div)
VIN (100mV/div)
VOUT (100mV/div)
VOUT (100mV/div)
Time (10s/div)
Time (10s/div)
NOTE 1: CIN = COUT = 4.7F -- 0603 size (1608 metric); C1 = C2 = 2.2F -- 0402 size (1005 metric) NOTE 2: CIN = COUT= C1 = C2 = 2.2F -- 0603 size (1608 metric)
7
SC652
Typical Characteristics (continued)
PWM Accuracy -- 4.2V
20 VIN = 4.2V, RISET = 4.99k, Calculated IBL = (100/RISET) x Duty Cycle
100
Percentage of Maximum IBL -- 4.2V
VIN = 4.2V, RISET = 4.99k
12
Percentage of Maximum IBL (%)
16
Calculated IBL (mA)
80
60
8
50kHz
200Hz
40
200Hz
50kHz
4
32kHz
20
32kHz
0 0 4 8 12 Measured IBL (mA) 16 20
0
0
20
40 60 PWM Duty Cycle (%)
80
100
PWM Accuracy -- 3.7V
20 VIN = 3.7V, RISET = 4.99k, Calculated IBL = (100/RISET) x Duty Cycle
100
Percentage of Maximum IBL -- 3.7V
VIN = 3.7V, RISET = 4.99k
12
Percentage of Maximum IBL (%)
16 Calculated IBL (mA)
80
60
8
50kHz
200Hz
40
200Hz
32kHz
4
32kHz
20
50kHz
0 0 4 8 12 Measured IBL (mA) 16 20
0 0 20 40 60 PWM Duty Cycle (%) 80 100
PWM Accuracy -- 2.9V
20 VIN = 2.9V, RISET = 4.99k, Calculated IBL = (100/RISET) x Duty Cycle
Percentage of Maximum IBL -- 2.9V
100 VIN = 2.9V, RISET = 4.99k
12
Percentage of Maximum IBL (%)
16
Calculated IBL (mA)
80
60
8
50kHz
200Hz
40
200Hz
32kHz
4
32kHz
20
50kHz
0 0 4 12 8 Measured IBL (mA) 16 20
0 0 20 40 60 PWM Duty Cycle (%) 80 100
8
SC652
Typical Characteristics (continued)
Start-up -- 0% to 50%
VIN = 3.7V, 0 to 50% duty cycle, RISET = 4.99k, fPWM = 32kHz
Start-up -- 0% to 100%
VIN = 3.7V, 0 to 100% duty cycle, RISET = 4.99k, no PWM 20mA
10mA IBL (10.0mA/div) 0mA-- IBL (10.0mA/div) 0mA--
VPWM (2V/div) 0V-- 50% Time (200ms/div)
VPWM (2V/div) 0V-- 100% Time (200ms/div)
IBL Settling Time -- 50% to 100%
VIN = 3.7V, RISET = 4.99k, fPWM = 32kHz 20mA IBL (10.0mA/div) 0mA-- 10mA IBL (10.0mA/div) 0mA--
IBL Settling Time -- 100% to 50%
VIN = 3.7V, RISET = 4.99k, fPWM = 32kHz 20mA 10mA
VPWM (2V/div) 0V-- 50% 100% Time (200ms/div)
VPWM (2V/div) 0V--
100%
50% Time (200ms/div)
DC Backlight Current -- 32kHz PWM
VIN = 3.7V, 50% duty cycle, RISET = 4.99k, IBL = 10mA
DC Backlight Current -- 200Hz PWM
VIN = 3.7V, 50% duty cycle, RISET = 4.99k, IBL = 10mA
IBL (10.0mA/div) 0mA--
IBL (10.0mA/div) 0mA--
VPWM (2V/div) 0V--
VPWM (2V/div) 0V--
Time (20s/div)
Time (1ms/div)
9
SC652
Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Pin Name
OUT IN ISET EN/PWM BL5 BL4 BL3 BL2 BL1 GND C2C1C1+ C2+
Pin Function
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 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 Negative connection to bucket capacitor 2 Negative connection to bucket capacitor 1 Positive connection to bucket capacitor 1 Positive connection to bucket capacitor 2
10
SC652
Block Diagram
C1+ C1- C2+ C213 IN 2
VIN
12
14
11
VOUT
Fractional Charge Pump (1x, 1.5x, 2x)
1
OUT
EN/ PWM
4
Control Interface and Level Converter
Oscillator
9 8 7
BL1 BL2 BL3 BL4 BL5
ISET
3
Current Setting Block
6 5
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: mize noise and support the output drive requirements of IOUT up to 90mA. For output currents higher than 90mA, a nominal value of 4.7F 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 1F. This may require the use of 2.2F capacitors to be sure that the degradation of capacitance due to DC voltage does not cause the capacitance to go below 1F. 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 (VF ) of the LEDs. A VF of 1.0V is supported when the input voltage is at 2.9V. Higher VF 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
* * *
A high efficiency fractional charge pump that supplies power to all LEDs Five matched current sinks that control LED backlighting current, providing 500A 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 1F to support the charge pump current requirements. The device also requires at least 1F capacitance on the IN pin and at least 1F capacitance on the OUT pin to mini-
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.
5 tHIGH_MIN = 1s
* *
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 165C, 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 20C 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.
4
Minimum Duty Cycle (%)
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
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.
C2
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
C1
GND
C2+ C1+ C1-
COUT
OUT IN
C2-
GND
GND
SC652
EN/ PWM BL5 BL4 BL3
BL1
CIN
ISET
BL2
IN
RSET
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
A D B DIMENSIONS DIM A A1 A2 b D E e L L1 N aaa bbb INCHES MIN .020 .000 .006 .077 .077 .010 .014 NOM (.006) .008 .079 .079 .016 BSC .012 .016 14 .003 .004 MAX .024 .002 .010 .081 .081 .014 .018 MILLIMETERS MIN 0.50 0.00 0.15 1.95 1.95 NOM MAX 0.60 0.05 0.25 2.05 2.05 0.35 0.45
PIN 1 INDICATOR (LASER MARK)
E
A2 A aaa C A1 LxN e/2 bxN bbb CA B C
(0.152) 0.20 2.00 2.00 0.40 BSC 0.25 0.30 0.35 0.40 14 0.08 0.10
SEATING PLANE
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 (C) G Z G P R X Y Z P Y INCHES (.079) .055 .016 .004 .008 .024 .102 MILLIMETERS (2.00) 1.40 0.40 0.10 0.20 0.60 2.60
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
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