LP3936SL National Semiconductor, LP3936SL Datasheet - Page 14

• Manufacturer Part Number: LP3936SL
• Manufacturer: National Semiconductor

Specifications of LP3936SL

• Operating Supply Voltage (typ): 3.3/5V
• Number Of Segments: 6
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: LAM CSP
• Pin Count: 32
• Mounting: Surface Mount
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (max): 6V
• Lead Free Status / Rohs Status: Compliant

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I
V
RDS
f
t
I
Symbol
LOAD
PWF
STARTUP
CL_OUT
OUT
Magnetic Boost DC/DC Converter Electrical Characteristics
PFM/PWM Mode
User can change the Boost converters mode between PWM (Pulse Width Modulation) and PFM (Pulse Frequency Modulation).
The startup is done on PFM mode and then the device runs on PWM mode (as a default). User can set PFM mode by turning
“pfm_mode” register bit HIGH. PFM is recommended to use with light loads and PWM with high loads.
Boost Standby Mode
User can set boost converter to STANDBY mode by writing register bit EN_BOOST low. This mode can be useful when driving
LEDs directly from battery voltage. This may be possible if LED forward voltage is low, battery voltage is high and LED current
is low.
When EN_BOOST is written high, the converter starts for 10 ms in PFM mode and then goes to PWM mode if PWM mode has
been selected (default). During Boost Start-up all LEDs are turned off to reduce the load.
Unused Boost Converter
If the boost converter is not used, it should be disabled by writing bit en_boost low. OUT pin should be connected to GND and
FB pin to the LED supply voltage.
Boost Converter Typical Performance Characteristics
otherwise stated.
ON
Load Current
Output Voltage Accuracy (FB Pin)
Output Voltage (FB Pin)
Switch ON Resistance
PWM Mode Switching Frequency
Frequency Accuracy
Startup Time
OUT Pin Current Limit
Boost Converter Efficiency
Parameter
3.0V ≤ V
V
1 mA ≤ I
3.0V ≤ V
V
1 mA ≤ I
3.0V
V
1 mA ≤ I
V
V
RT = 82 kΩ
RT = 82 kΩ
V
OUT
OUT
(SCHOTTKY)
IN
DD1,2
DD
20081419
>
= 3.6V
<
= 4.55V
= 4.55V
4.55V + V
= 3.6V, I
V
LOAD
LOAD
LOAD
IN
IN
IN
≤ 4.5V
≤ V (FB)−0.5V
Conditions
<
≤ 225 mA
≤ 250 mA
≤ 250 mA
4.55V +
SW
14
(SCHOTTKY)
= 0.5A
Boost Frequency vs RT Resistor
Min
−10
600
400
−5
−6
0
V
V
IN
IN
= 3.6V, V
–V
(SCHOTTKY)
4.55
Typ
750
0.4
±
25
1
3
OUT
= 4.55V if not
1050
1200
Max
250
+10
0.5
+5
+6
20081420
Units
MHz
mA
mA
ms
%
%
Ω
V
V