LTC3455 Linear Technology Corporation, LTC3455 Datasheet
LTC3455
Available stocks
Related parts for LTC3455
LTC3455 Summary of contents
Page 1
... DC/DC converters, a USB power controller, a full-featured Li-Ion battery charger, a Hot Swap output, a low-battery indicator, and numerous internal protection features. The LTC3455 provides a small, simple solution for obtaining power from three different power sources: a single-cell Li-Ion battery, a USB port, and a wall adapter. Current drawn from the USB bus is accurately limited under all conditions ...
Page 2
... ON2 = 1V MODE = 1.35V WALLFB = 0V 100µA ON PBSTAT = 0V 1mA ON PBSTAT = 100µA = 1mA U W TOP VIEW ORDER PART NUMBER LTC3455EUF 18 FB2 HSON 14 HSO UF PART 13 HSI MARKING 3455 UF PACKAGE = 36°C/W, θ ...
Page 3
... MODE = V = 0.85V FB1 FB2 = 5V USB = 5V USB USBHP = 5V USB USBHP = 5V USB SUSPEND = 0.5V SUSPEND = 0.5V USBHP = 3.3V HSI = 3.3V 2.5V HSI HSO LTC3455 = 3.6V 2V open, V PWRON ON ON2 MIN TYP MAX 0.15 2.5 4.0 0.4 0.9 ● 0.784 0.805 0.826 –8 0 ±1 ±25 ● 1.0 1.8 0.8 ● 0.784 0.805 0.826 ...
Page 4
... Maximum Rating condition for extended periods may affect device reliabilty and lifetime. Note 2: The LTC3455 is guaranteed to meet specified performance from 0°C to 85°C and is designed, characterized and expected to meet these extended temperature limits, but is not 100% tested at –40°C and 85°C. ...
Page 5
... G08 USB Undervoltage Lockout 4.00 3.75 FALLING RISING 3.50 3.25 3.00 2.75 2.50 –50 – 100 125 TEMPERATURE (°C) 3455 G11 LTC3455 Switching Regulator Current Limit 1000 SWITCHER 2 800 SWITCHER 1 600 400 200 0 – 100 125 –25 0 TEMPERATURE (°C) 3455 G06 HSO Pin Current Limit ...
Page 6
... LTC3455 W U TYPICAL PERFOR A CE CHARACTERISTICS Battery Charger Regulation Voltage 4.30 4.25 4.20 4.15 4.10 4.05 4.00 – 100 –25 0 TEMPERATURE (°C) 3455 G13 Charge Current When Wall-Powered 600 500 400 THERMAL CONTROL LOOP IN OPERATION 300 200 V = 3.6V 100 BAT V = 4.5V MAX R = 2.49k PROG 0 –50 – 100 TEMPERATURE (° ...
Page 7
... LDOs or Switchers for LCD bias, white LED backlight drive, etc). , from this pin PROG When the LTC3455 is on and neither USB or wall power are available, an internal PMOS switch connects this pin to the V pin. When either USB or wall power is present, they ...
Page 8
... PWRON pin is pulled high by a microcontroller to keep the LTC3455 turned on momentary-on switch is not used, this pin can be held to ground to keep on the LTC3455. Leave ON open if not used. This pin has a weak pull-up current source. GND (Pin 25 – Exposed Pad): Ground Pin. The exposed ...
Page 9
... BURST MODE ENABLE HSON 15 – 3. 1000 BATTERY CHARGER 1 1000 – 1.23V R 2.41R + + 4R CHARGE R CONTROL – + 0.8V UVLO + – EXTPWR LTC3455 3.32k WALLFB EXTPWR + 11 1.24k – 1.23V BATTERY PMOS SWITCH V MAX 10 SWITCHER 1 4.7µH SW1 PWM 7 DRIVER 100k FB1 – 1 80.6k + 0.8V ENABLE SWITCHER 2 4.7µH SW2 ...
Page 10
... U U APPLICATIO S I FOR ATIO Undervoltage Lockout (UVLO external power is present, the LTC3455 will start only if the battery voltage is above 3.0V. This prevents starting up with a battery that is too close to deep discharge. Once started, the battery must drop below 2.6V before the LTC3455 will shut off. This hysteresis is set intentionally ...
Page 11
... U U APPLICATIO S I FOR ATIO Operation When No Battery Is Present As long as USB or wall power is available, the LTC3455 will operate with no battery present, a crucial requirement for systems with a removable battery. Keep in mind, however, that if the LTC3455 is USB powered and the battery is not present, absence of the battery means that there is no reservoir if the system needs more power than the USB port can supply ...
Page 12
... There are three basic modes for the USB power manager: high power, low power, and suspend. High power mode allows the LTC3455 to draw up to 500mA from the USB port, and is selected by pulling the USBHP pin high. Low power mode reduces the allowable current drawn to 100mA, and is selected by pulling the USBHP pin low ...
Page 13
... Many portable devices have nominal loads that can easily be supported by the USB supply, but they have brief transient loads that can exceed the maximum available USB power. The LTC3455 is designed to handle these overloads while drawing as much power as possible from the USB port. If the USB bus is providing power but the ...
Page 14
... PWRON signal low. When the push-button is released, the ON pin goes high and the LTC3455 turns off. The ON and PWRON pins enable Switcher 1 (along with all the internal circuits needed for normal operation), and the ON2 pin enables Switcher 2 ...
Page 15
... Reset Signal (RST) A 200ms reset signal (the RST pin is pulled low) is provided for proper initialization of a microcontroller when- ever the LTC3455 is first turned on, either by the ON or PWRON pins the application of external power. The RST signal is also pulled low whenever the entire LTC3455 ...
Page 16
... Schottky diode. The most important MAX specification in picking this diode is its reverse leakage current. When the LTC3455 is turned on but wall power is not present, the Schottky will leak current to ground through the WALLFB resistor divider (see Figure 5). This leakage current should be minimized (by picking an appro- priate low-leakage Schottky diode can dramatically reduce Burst Mode efficiency at light loads ...
Page 17
... Table 1 shows several inductors that work well with the LTC3455. These inductors offer a good compromise in current rating, DCR and physical size. Consult each manu- facturer for detailed information on their entire selection of inductors ...
Page 18
... This trace shows excessive ringing when the 5V cable is inserted, with the overvoltage spike reaching 10V; more than enough to damage the LTC3455. For the bottom trace, a 1Ω resistor is added in series with the 4.7µF capacitor to locally bypass the 5V input. This trace shows the clean response resulting from the addition of the 1Ω ...
Page 19
... U Tie the MODE pin to V Mode operation. Even when the MODE pin is high, the LTC3455 will only enter Burst Mode when the load current is low. For many noise-sensitive systems, Burst Mode operation might be undesirable at certain times (i.e. during a transmit or receive cycle of a wireless device), but highly desirable at others (i ...
Page 20
... If the battery voltage is below 4.05V at the end of this cycle, the LTC3455 will start a new charge cycle. This action will continue until the battery voltage exceeds the 4.05V thresh- old. This operation is typically seen only when charging from USB power ...
Page 21
... F11 reapplied, the PROG pin is floated temporarily, or the SUSPEND pin is temporarily pulled high (if the LTC3455 is under USB power). The device will still operate normally from USB or wall power even if the charger has turned off due to a trickle-charge timeout ...
Page 22
... USB cables. Figure 13 shows this reduction in charge current. Because the charge current can vary dramatically when the LTC3455 is USB powered, battery charging can take considerably longer using the USB supply (as compared to a wall adapter). Constant-Current-Only Charger/Disabling the ...
Page 23
... The Hot Swap output can only operate when the LTC3455 is on, and is enabled using the HSON pin. If this hot-plugging protection is not needed, this output can be used as a load switch for other devices within the system. ...
Page 24
... LTC3455 U U APPLICATIO S I FOR ATIO V OUT1 C1 VIAS TO LOCAL GROUND PLANE. Figure 15. Recommended Board Layout and Component Placement for Power Sections of LTC3455 (Refer to Schematic on Back Page GND D1 GND USB WALL BAT MAX ADAPTER L2 V OUT2 C2 C7 ...
Page 25
... Standalone USB Power Supply with Temporary Backup Power Although designed primarily for Li-Ion powered portable applications, the LTC3455 is also a good choice for systems that are always powered by a USB supply or wall adapter. The battery charger can then be used to charge up a large capacitor or backup battery, which briefly provides power to the system after the external power has been removed ...
Page 26
... Figure 17 shows how to implement a higher current 3.3V output using the LTC3455. By adding one tiny SOT23 PMOS and using the AI/AO amplifier as an LDO, the 3.3V output now provides 1.2A of output current. Switcher 2 is programmed for an output voltage of 3 ...
Page 27
... UF Package 24-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1697) 0.70 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 0.75 ± 0.05 2.45 ± 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LTC3455 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP 0.115 0.35 × 45° CHAMFER TYP 23 24 0.40 ± 0. (UF24) QFN 0105 0.25 ± ...
Page 28
... McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 8 USB MODE 6 HSON SUSPEND USB ON2 5 CONTROLLER USBHP PWRON RST 10 V MAX PBSTAT C5 10µF LTC3455 1k 4 CHRG ON 11 WALLFB HSO C8, 0.1µF 3 TIMER 2 PROG HSI 2.49k 9 SW2 V BAT C4 4.7µF FB2 1.8V ...