TB62736FUG
TOSHIBA BiCD Digital Integrated Circuit Silicon Monolithic
TB62736FUG
Step-up Type DC-DC Converter for White LEDs
The TB62736FUG is a high efficiency step-up type DC/DC converter that is designed especially for use as a constant current driver of white LEDs. It is possible to drive 2 - 6 white LEDs connected in series using a lithium-ion battery. (Typ. 4 White LEDs) This IC incorporates an N-ch-MOS transistor required for switching of an external inductor. The forward current of the LEDs can be controlled by an external resistor. An analog voltage input and a pulse input system (PWM) can be used as a brightness control function. The switching frequency is fixed at around 1.1 MHz. This IC is best suited for use as a driver of white LED back lighting in color LCDs in PDAs, cellular phones and handy terminal devices.
Weight: 0.016 g (typ.)
Features
* * * * * * * Brightness control function Maximum output voltage : LED forward current 25~100% : over 24V : 20mA (typ.) @ RSENS=16 : 400 mW : SSOP6-P-0.95 (SOT23-6) : maximum 87% (when used with components as recommended herein)
LED current values controlled by external resistance Output power Package High efficiency
Thermal Shutdown Function incorporated : 150 degree (typ.)
Pin Assignment (top view)
SHDN
FB
M
(NC)
GND
VIN
SW
Note 1: The IC may break if mounted 180 degrees in reverse. Ensure the device is correctly orientated before
assembley.
Note 2: The control pin must be set to a certain logic level, as unstable output could result if the pin is left open.. Note 3: Regarding soldering, the following conditions were confirmed
(1) Use of Sn-63Pd solder bath solder bath temperature = 230C, dipping time = 5 seconds, number of times = once, use of R-type flux (2) Use of Sn-3.0Ag-0.5Cu solder bath solder bath temperature = 245C, dipping time = 5 seconds, number of times = once, use of R-type flux
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TB62736FUG
Block Diagram
4 3 VIN Reference Mono Multi
SW
2
NC
Off Time Control Mono Multi CTL AMP.
Level Detect Error AMP. 1 SHDN GND CTL AMP. 5 6
Pin Functions
No. Symbol Function Input pin for IC ON/OFF control and variable LED IF. 0 to 0.5V : Shutdown Mode (IC shutdown) 1.0V to 2.5V : IF = 25 to 100% Variable (Linear Control) Over 2.5V : IF = 100% PWM signal input for IF control (see p.5) No Connection or Connected to GND Supply voltage pin. Supply voltage range : 2.8V to 5.5V DC-DC converter switching pin - switch incorporates N-ch MOSFET Ground pin Connected to the cathode of LED
1
SHDN
2 3 4 5 6
NC VIN SW GND FB
Note: The NC terminal is not connected to the internal circuit.
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TB62736FUG
Absolute Maximum Ratings (Topr = 25C, unless otherwise specified)
Characteristics Power supply voltage Input voltage Switching pin voltage Switching pin current Symbol VIN Vin VO (SW) IO (SW) Ratings -0.3 to 6.0 -0.3 to VCC + 0.3 -0.3 to 24 380 0.41 (IC only) Power Dissipation PD 0.47 (IC mounted on PCB) (Note) 300 (IC only) 260 (IC mounted on PCB) -40 to 85 -40 to 150 125 C/W C C C W Unit V V V mA
Rth (j-a) 1 Thermal resistance Operating temperature range Storage temperature Maximum junction temperature Rth (j-a) 2 Topr Tstg Tj
Note: Power dissipation is reduced by 3.8mW/C from the maximum rating for every 1C exceeding the ambient temperature of 25C (when the IC is mounted on a PCB).
Recommended Operating Condition (Topr = -40 to 85C, unless otherwise specified)
Characteristics Power supply voltage SHDN pin H level input voltage SHDN pin L level input voltage SHDN pin input pulse width LED current (Average value) Symbol VIN VSHDN (H) VSHDN (L) tpw IO1 Test Conditions ON/OFF duty width VIN = 3.6 V, RSENS = 16 4LEDs, Topr = 25C Min. 2.8 2.7 0 33 Typ. 20 Max. 5.5 VIN 0.5 Unit V V V s A
Electrical Characteristics (Topr = -40~85C VCC = 2.8~5.5 V, unless otherwise specified)
Characteristics Operating consumption current Standby consumption current SHDN pin current Integrated MOS-FET switching frequency Switching pin protection voltage Switching pin current Switching pin leakage current FB pin feedback voltage FB pin line regulation Symbol IIN (ON) IIN (OFF) ISHDN fOSC VO (SW) IO (SW) IOZ (SW) VFB VFB Test Conditions VIN = 6.0 V, RSENS = 16 VIN = 3.6 V, VSHDN = 0 V VIN = 3.6 V, VSHDN = 3.6 V VIN = 3.6 V, VSHDN = 3.6 V VIN = 3.6 V, RSENS = 16 Topr = 25C, L = 4.7H VIN = 3.6 V center VIN = 3.0V to 5.0V Min. -10 0.77 308 -5 Typ. 0.9 0.5 0 1.1 25 400 0.5 325 Max. 1.5 1.0 10 1.43 1 342 5 Unit mA A A MHz V mA A mV %
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Application Circuit Example
VIN 4.7-10H 4 3 VIN Reference Mono Multi Off Time Control Mono Multi CTL AMP. 2.2F Level Detect 1.0-2.5V Analog 1 PWM SHDN GND CTL AMP. 5 Error AMP. 6 FB 16 @20mA 500 1F Vz=24V SW 2 NC
Protection at the time of LED opening
The zener diode in the application circuit example is necessary for the provision of over-voltage protection for when the LED becomes open. As the IC does not incorporate a voltage protection circuit, it is strongly advised that a zener diode be connected. The zener diode should satisfy the following conditions: i) Less than maximum output voltage of 24V ii) Greater than the total series LED VF iii) Less than the maximum output capacitance C2. Moreover, by connecting a protection circuit such as R_ZD in the figure below, it is possible to control the output current when the LED becomes open, and to use a zener diode of lower tolerance. An example of IZD control by R_ZD connection. (RSENS = 16 )
S-Di R_DZ () 500 100 IZD (mA) 0.6 1.0 GND FB RSENS SW IZD 1 F C2 R_ZD IF
In order to avoid adverse effects on driver characteristics, Toshiba recommends a resistance of 500 ohms or less.
Protection circuit application
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Output-side Capacitor Setting
It is recommended that the value of C2 be equal to, or greater than 1.0 (F).
External Inductor Size Setting
For each number of LEDs, the selected inductance should be greater than the value indicated in the table below.
Number of LEDs 2 3 4 5 6 10 Inductance (Unit: H) 4.7 6.8 IF = 20 mA Note
Control of IF
The resistance RSENS is connected between the FB pin and the GND pin. The average current is controlled by the RSENS value, and calculated using the following equation: IF (mA) = [ 325mV / RSENS() ] Margin of error is 5%.
Current control using SHDN pin
This IC can carry out variable of the IF current by external resistance Variable range : 30 to 100% SHDN Voltage VSHDN=0V~0.5V VSHDN=1V~2.5V VSHDN>2.5V Note Io Valuable Rate 0 25 - 100 100 UNIT : %
SHDN input - output rate/output current VIN=3.0V
100 80 IF rate (%) 60 40 20 0 1.0
25 20 IF(mA) 15 10
IF rate IF
5 0
1.3
1.6 1.9 VSHDN(V)
2.2
2.5
Dimming using PWM signal input
A dimming function can also by applied using a PWM signal. [Notes] When using a PWM signal, the minimum pulse width of the PWM should be greater than 33s. Duty ratio of PWM function should be set at 10% - 90%. The recommended PWM frequency should be 100Hz - 10kHz. < |
