DT1685-V1.1

DT1685 consists of step-down switchingregulator with PWM control. The device includes a reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc.

DT1685 provides low-ripple power, high efficiency, and excellent transient

characteristics. The PWM control circuit is able to the duty ratio linearly forms 0 up to 100%. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP-8L-EP

package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 38V, it is also suitable for the operation via an AC adapter.  FEATURES

- Input voltage：8V to 38V

- Adjustable version output voltage range form 3.3V to 38V - Duty ratio：0% to 100% PWM control - Oscillation frequency：100K/350 KHz - Enable and auto restart function.

- Thermal Shutdown function / Internal OVP. - Short Circuit Protect (SCP).

- Built-in internal SW P-channel MOS. - SOP-8L-EP Pb-Free package.

 BLOCK DIAGRAM

EN/CTVCC

CURRENTSOURCEBIAS1.23VREFERENCE2.5V REGULATOR START-UP and Auto restart controlSENSE21.1V1.25VOSC.Current limitCOMP.140mV+FB

+AMP_+COMP.SENSE1SENSE2

_AMP++AMP_CONTROL + DRIVEROVPThermalShutdownLineCompensation0.35VSCP

 PIN ASSIGNMENT

The package of DT1685 is SOP-8L-E

( Top View )

EN/CTVSSVGATEVCC

1234SOP–8L–EP

SWDT1685the pin assignment is given by:

8765Name Description

EN/CT ON/OFF and auto restart control VSS GND pin

FB

Driver gate clamping pin. The pin

VGATE

SENSE2must connect a 1uF capacitor to VCC

VCC Operating voltage input SENSE1

Switch pin. Connect external inductor SW SW

and diode here

SENSE1 Current sense input1 SENSE2 Current sense input2

FB Feedback pin

 ORDER/MARKING INFORMATION Order Information Top Marking Logo T16 85XXXXFrequencyPackage TypePackingBlank : 100KHz ES: SOP-8L-EPBlank : TubeA: 350KHzA : Taping T __VGATESWVSS

168 5 YYWWX Part numberID code: internalWW: 01~52Year: 10=2010 11=2011

 ABSOLUTE MAXIMUM RATINGS (at TA = 25°C)

Characteristics

Symbol

Rating

Unit

VCC Pin Voltage Feedback Pin Voltage EN/CT, OVP Pin Voltage SENSE1,SENSE2 Pin Voltage Switch Pin Voltage Power Dissipation Storage Temperature Range Operating Temperature Range Operating Supply Voltage Output Current

Thermal Resistance from Junction to case Thermal Resistance from Junction to ambient

=

VCC VFB VSW PD TST TOP VOP IOUT

VSS - 0.3 to VSS + 40 VSS - 0.3 to 6 VSS - 0.3 to 38 VSS - 0.3 to VCC + 0.3

-40 to +165 -20 to +125 +8 to +38 0 to 3

V V V V °C °C V A

VSS - 0.3 to VCC V (TJ – TA)/ θJA W θJC 15 °C/W θJA 40 °C/W

Note : θJA is measured with the PCB copper are (need connect to Exposed pad) of approximately 1 in2(Multi-layer).

 ELECTRICAL CHARACTERISTICS (VCC=12V, TA=25°C, unless otherwise specified)

Characteristics

Under Voltage Lockout UVLO Hysteresis

OVP detect voltage Line Regulation Load Regulation Quiescent Current Oscillator frequency Max. Duty Cycle (ON) Min. Duty Cycle (OFF) Internal MOSFET RDSON Sense Voltage

Sense Voltage Hysteresis EN/CT pin logic input threshold

Symbol

Conditions

Min Typ Max Units -

6

-

V FB VFB

IOUT10mA 1.08 1.10 1.12 V

- 0.8 - V 1.212 1.250 1.280 V - 0.5 1 % - 0.3 0.6% mV -

3

6

mA

UVLO Falling - VOVP - VCC=10 ~ 40V

IOUT=0 ~ 1A, -

RSENSE = 140mΩ ICCQ VFB > 1.2V

DT1685 80 100 120 FOSC KHz

DT1685A 28 350 420 Force driver on - 100 - VFB = 0.7V DC %

Force driver off - 0 - VFB = 1.2V

RDSON VCC=12V, VFB = 0.7V - 110 170 mΩ VSENSE VSENSE1-VSENSE2 110 125 140 mV VSENSE-h

VEN1 Shutdown mode

- 40 - mV -

0.4 V voltage restart, VFB<0.4V 0.5 VCT Auto VEN2 Operating mode

1.6

IEN/CT-C Charge current

IEN/CT-D Discharge current TSD TSH

- 1.5 - - EN/CT pin current

EN/CT pin current

Thermal shutdown Temp Thermal Shutdown Hysteresis  APPLICATION CIRCUIT

(1) AL CAPACITOR

- -32 - uA - 1.5 - uA - 160 - °C - 40 - °C C1VCC=10~36VL1D1C3470uC40.1uC51u4321C90.1uU1VCCVGATEVSSEN/CTSWSENSE1SENSE2FB5678B340A10NVOUT=5.0V/2AR-sense50mRR3C7470uC839K0.1uOptionC2R711KDT1685

VOUT=1.1V×(1+

R3) R4

L1 recommend value (VIN=10~30V ,VOUT=5V, IOUT=1A) Version DT1685 DT1685A L1 Value (H)

(2) MLCC

C1VCC=10~36VL1D1C322uC40.1uC51u4321C90.1uU1VCCVGATEVSSEN/CTSWSENSE1SENSE2FB567811KR7B340AC622uC722uC839K0.1uOption22uHR-sense50mRR3C210NVOUT=5.0V/2A66u 22u

DT1685

 FUNCTION DESCRIPTIONS SENSE1/2

The current limit sense pin, if VSENSE1-VSENSE2≧140mV, the over current is happened that it can turn-off driver cycle by cycle.

EN/CT

The pin is enable/shutdown and auto restart control functions. When system is normal operating, this pin is enable/shutdown function. Pulling this pin below a threshold voltage of under 0.4V shuts the regulator off, and pulling this pin from 0.5V to 1.5V turns the regulator on. However when VOUT is short (VFB<0.4V), the auto restart function can be started that restart the regulator cycle by cycle. The cycle time is set by outside capacitor (C6). Please refer the below waveform and formula, the t2 cycle is regulator off time and t1 cycle is current limit time. The charge-current is 30uA and discharge-current is 1.4uA.

Iin (A)

Current Limit

Time

VEN/CT1.5V0.5V0t2t1Time

1

(Sec.)32u 1

(Sec.)t2=C6×1.5ut1=C6×

Under Voltage Lockout (UVLO)

To avoid mis-operation of the device at low input voltages an under voltage lockout is included that disables the device, if the input voltage falls below 6.0V.

Current Limit Protection

The Current limit is set by outside resistance (RSENSE), When the SENSE1-SENSE2 voltage larger than 140mV, the current limit is happened that driver can be turned off until the drop is small than 110mV. The current limit set according to the following equation:

125m+(125-45)m

Current Limit (A)=

2xRSENSE

The maximum output current table is shown as below; please refer the table to design.

RSENSE (Ω)

Maximum Output Current (A)

33m 3.0 50m 2.0 100m 1.0

Freq =350KHz

Freq =100KHz

Thermal Considerations

The SOP-8L-EP package needs a heat sink under most conditions. The heat sink connect exposed pad of DT1685 to obtain best effect. The size of the heat sink depends on the input voltage, output voltage, output current and ambient temperature.  TYPICAL CHARACTERISTICS

DT1685A

DT1685

 TYPICAL CHARACTERISTICS (CONTINUOUS)

100KHz 350KHz

VCC=32V, VOUT=5V, IOUT=1.2A, CEN=0.1u COUT=470u

VCC =32V, VOUT=5V, IOUT=1.0A,

CEN=0.1u, COUT=40u

 TYPICAL CHARACTERISTICS (CONTINUOUS)

VCC=12V, VOUT=5V, IOUT=0~2A VCC=32V, VOUT=5V, IOUT=0~2A

VCC=32V, VOUT=1.2V, IOUT=1.5A Thermal Shutdown Release VCC=32V, VOUT=5V, IOUT=1.5A Short Circuit Release

 PACKAGE OUTLINES

XExpose PadYEHθLDETAIL A

bD7(4X)A2ACyA1e

DETAIL A

Dimensions in Millimeters Dimensions in Inches Min. Nom. Max. Min. Nom. Max.

A - - 1.75 - - 0.069 A1 0 - 0.15 0 - 0.06 A2 1.25 - - 0.049 - - C 0.1 0.2 0.25 0.0075 0.008 0.01 D 4.7 4.9 5.1 0.185 0.193 0.2 E 3.7 3.9 4.1 0.146 0.1 0.161 H 5.8 6 6.2 0.228 0.236 0.244 L 0.4 - 1.27 0.015 - 0.05 b 0.31 0.41 0.51 0.012 0.016 0.02 e 1.27 BSC 0.050 BSC y - - 0.1 - - 0.004 X - 2.34 - - 0.092 - Y - 2.34 - - 0.092 - θ 0O - 8O 0O - 8O Mold flash shall not exceed 0.25mm per side JEDEC outline: MS-012 BA Symbol