 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
ADP3802AR Datasheet(PDF) 11 Page - Analog Devices |
|
||||||||||||||||||||||||||||||
ADP3802AR Datasheet(HTML) 11 Page - Analog Devices |
|
|
11 / 20 page  ADP3801/ADP3802 –11– REV. 0 ADP3800 COMP EOC (a) EOC Output Terminates Charge 270 2N3906 ADP3800 EOC VL 100k 0.1 F (b) EOC Turns on LED to Signal Charge Completion 2N3904 2 ADP3800 EOC VL COMP 100k 100k 2N3906 0.1 F 10k 20k 20k 270 (c) EOC Terminates Charge and Turns on LED 100k ADP3800 EOC *LEVEL SHIFTED TO TO DRIVE PMOS VL 100k 100k 2N3906 1 F COMP RESET J K Q Q 74H73A BATSELB* A/B + BATSELA* 100k 0.1 F 20k 2N3904 2 10k (d) Flip-Flop Switches Between Batteries on EOC Signal Figure 23. EOC Output Circuits COMP Node Both the current loop and the voltage loop share a common, high impedance compensation node, labeled COMP. A series capacitor and resistor on this node help to compensate both loops. The resistor is included to provide a zero in the loop response and boost phase margin. The voltage at the COMP node determines the duty cycle of the PWM. The threshold levels are typically 1.0 V for 0% duty cycle and 2.0 V for 100% duty cycle, resulting in a total range of 1.0 V. When the ADP3801/ADP3802 first turns on, the COMP capacitor is at 0.0 V. It has to charge up to at least 1.0 V before the duty cycle rises above 0% and the pass transistor turns on. This “soft-start” behavior is desirable to avoid undue stress on the external components. In addition, whenever the part is placed in Shutdown or in UVLO, the COMP capacitor is dis- charged to ensure soft start upon recovery. The current available to charge and discharge the COMP ca- pacitor during normal operation is 100 µA. Thus, the slew rate at this node is equal to 100 µA divided by the capacitor. For a typical capacitance of 1 µF, the slew rate is 0.1 V/ms. Thus, it takes about 10 ms before the ADP3801/ADP3802 starts to operate from a soft-start state. This is regardless of the internal oscillator frequency. One important note is that the COMP node is a high impedance point. Any external resistance or leak- age current on this node will cause an error in both the charge current control and the final battery voltage. Gate Drive The ADP3801/ADP3802 gate drive is designed to provide high transient currents to drive the pass transistor. The rise and fall times are typically 20 ns and 200 ns respectively when driving a 1 nF load, which is typical for a PMOSFET with RDS(ON) = 60 m Ω. Figure 15 shows the typical transient response of the output stage driving this load from a 10 V supply. A voltage clamp is added to limit the pull-down voltage to 7 V below VCC. For example, if VCC is 10 V then the output will pull down to 3 V minimum, limiting the VGS voltage applied to the external FET. Low Dropout Regulator and Reference A 3.3 V LDO is used to generate a regulated supply for internal circuitry. Additionally, the LDO can deliver up to 10 mA of current to power external circuitry such as a microcontroller. A 1.0 µF capacitor must be placed close to the VL pin to ensure stability of the regulator. Due to the design of the regulator, stability is not contingent on the ESR for the output capacitor. Many different types of capacitors can be used providing flex- ibility and ease of design. The LDO also includes a high accu- racy, low drift internal reference equal to half of VL to set levels within the part. During shutdown and UVLO, both the refer- ence and the LDO remain active. Shutdown The IC may be placed in shutdown at any time to stop charging of the batteries and to conserve power. For example, to safely switch from one battery to the next, the part should be shut down to momentarily interrupt charging. Also, if the batteries have completed charging or no batteries are present, then the part may be placed in shutdown to save power. A logic low on |
Similar Part No. - ADP3802AR |
|
Similar Description - ADP3802AR |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
