LP3933SL NSC [National Semiconductor], LP3933SL Datasheet - Page 8

• Manufacturer Part Number: LP3933SL
• Description: Lighting Management System for Six White LEDs and Two RGB or FLASH LEDs
• Manufacturer: NSC [National Semiconductor]

www.national.com
SPI Interface
SPI Timing Parameters
V
Magnetic Boost DC/DC Converter
The LP3933 boost DC/DC Converter generates 4.1V–5.3V supply voltage for the LEDs from single Li-Ion battery (3V…4.5V). The
output voltage is controlled with 8-bit register in 9 steps. The converter is a magnetic switching PWM mode DC/DC converter with
a current limit. The converter has 1 MHz switching frequency when timing resistor RT is 82 KΩ.
The topology of the magnetic boost converter is called CPM control, current programmed mode, where the inductor current is
measured and controlled with the feedback. The user can program the output voltage of the boost converter. The control changes
the resistor divider in the feedback loop.
The following figure shows the boost topology with the protection circuitry. Three different protection schemes are implemented:
1. Over voltage protection, limits the maximum output voltage
2. Over current protection, limits the maximum inductor current
3. Duty cycle limiting, done with digital control.
DD1,2
— Keeps the output below breakdown voltage.
— Prevents boost operation if battery voltage is much higher than desired output.
— Voltage over switching NMOS is monitored, too high voltages turn the switch off.
= V
DD_IO
= 2.775V
(Continued)
Note: Data guaranteed by design.
Symbol
10
11
12
1
2
3
4
5
6
7
8
9
Cycle Time
Enable Lead Time
Enable Lag Time
Clock Low Time
Clock High Time
Data Setup Time
Data Hold Time
Data Access Time
Output Disable Time
Output Data Valid
Output Data Hold Time
SS Inactive Time
Parameter
SPI Timing Diagram
8
Min
70
35
35
35
35
20
10
0
0
Limit
Max
20
10
20
Units
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
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