ltc3252 Linear Technology Corporation, ltc3252 Datasheet
ltc3252
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ltc3252 Summary of contents
Page 1
... Low operating currents (60 A with both outputs enabled with one output enabled) and low external parts count make the LTC3252 ideally suited for space-con- strained battery-powered applications. The part is short- circuit and overtemperature protected and is available in a tiny 4mm 3mm 12-pin DFN package ...
Page 2
... EN2 = EN1 = 0V, EN2 = OUT 0 I 250mA 250mA OUT1 OUT2 V = 3.0V 200mA 0.74V (Note 5) IN OUT ORDER PART NUMBER 12 FB2 11 EN2 LTC3252EDE + OUT2 – PART 7 GND MARKING 3252 = 4.3 C OUT1 OUT2 MIN TYP MAX UNITS 2.7 5.5 60 100 ...
Page 3
... Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3252EDE is guaranteed to meet specified performance from Specifications over the – and 85 C operating temperature range are assured by design characterization and correlation with statistical process control ...
Page 4
... LTC3252 W U TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Max/Min Frequency vs Supply Voltage 2.0 1.9 1 MAX –40 C MAX 1.7 1 MAX 1.5 1.4 1.3 1 MIN 1.1 –40 C MIN 1 MIN 0.9 0.8 2.7 3.7 4.2 4.7 5.2 3.2 V (V) IN 3252 G07 Output Current Transient Response 250mA I OUT 20mA V OUT 20mV/DIV 3. 1.5V OUT CTIO S FB1 (Pin 1): Feedback Input Pin 1 ...
Page 5
... OUT2 to FB2 to program the O2 output voltage. W EN1 EN2 2 11 SWITCH SPREAD SPECTRUM CONTROL CHARGE PUMP 1 – BURST DETECT CIRCUIT + – GND LTC3252 OSCILLATOR + OUT1 – FB1 CHARGE PUMP OUT2 – FB2 3252 SBD ...
Page 6
... C, the thermal shutdown cir- cuitry will disable the charge pumps. The IC resumes operation once the junction temperature drops back to approximately 155 C. The LTC3252 will cycle in and out of thermal shutdown without latchup or damage until the overstress condition is removed. Long term overstress ...
Page 7
... The LTC3252 will remain in the low current operating state until either output has dropped enough to require another burst of current. The LTC3252 resumes continuous operation when the load on one or both outputs exceeds the internally set threshold. Unlike traditional charge pumps where the burst current is highly dependant on many factors (i ...
Page 8
... PC board trace. V Capacitor Selection IN The low noise, dual phase architecture used by the LTC3252 makes input noise filtering much less demanding than conventional charge pump regulators. The LTC3252 input current will transition between I each half cycle of the oscillator. The blanking period described in the V this reason it is recommended that a low ESR 4 ...
Page 9
... The large dv/dt on these pins can couple energy capacitively to adjacent printed circuit board runs. Magnetic fields can also be generated if the flying capacitors are not close to the LTC3252 (i.e., the loop area is large). To decouple capacitive energy transfer, a Faraday shield may be used. This is a grounded PC trace between the sensitive node and the LTC3252 pins ...
Page 10
... Programming the LTC3252 Output Voltages (FB1 and FB2 Pin) Each output of the LTC3252 is programmed to an arbitrary voltage via an external resistive divider. Figure 7 shows the required voltage divider connection. The voltage divider ratio is given by the expression: ...
Page 11
... FB1 GND 510k U DE/UE Package 12-Lead Plastic DFN (4mm 3mm) (Reference LTC DWG # 05-08-1695) 0.58 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 3.30 0.05 (2 SIDES) 4.00 0.10 (2 SIDES 0.20 TYP 3.00 0.10 1.70 0.10 (2 SIDES) (2 SIDES) 0.75 0.05 0.00 – 0.05 LTC3252 OUT2 1.5V 250mA 470k 1 F 4.7 F 510k 3252 TA02 0.38 0. 0.115 TYP 7 12 PIN 1 NOTCH (UE12/DE12) DFN 0802 6 1 0.25 0.05 0.50 BSC 3.30 0.10 (2 SIDES) BOTTOM VIEW— ...
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... Q SHDN 95% Efficiency 2.5V to 5.5V < MS10 Q SHDN www.linear.com EN2 EN2 EN1 EN1 OUT2 OUT1 C2 261k 1 F LTC3252 – – C1 FB2 4 FB1 GND EN1 412k 100k OFF OFF Min = 1.24V, OUT = 1 ...