MAX1705 Maxim, MAX1705 Datasheet - Page 17

• Manufacturer Part Number: MAX1705
• Description: 1- to 3-Cell / High-Current / Low-Noise / Step-Up DC-DC Converters with Linear Regulator
• Manufacturer: Maxim

Figure 9. Typical Phone Application
Table 5. Typical Available Output Current
To implement soft-start, set CLK/SEL low on power-up;
this forces PFM operation and reduces the peak switch-
ing current to 435mA. Once the circuit is in regulation,
CLK/SEL can be set high for full-power operation.
A momentary pushbutton switch can be used to turn
the MAX1705/MAX1706 on and off (Figure 10). ONA is
pulled low and ONB is pulled high to turn the part off.
When the momentary switch is pressed, ONB is pulled
low and the regulator turns on. The switch must be
pressed long enough for the microcontroller (µC) to exit
reset (200ms) and drive ONA high. A small capacitor is
added to help debounce the switch. The µC issues a
logic high to ONA, which holds the part on regardless
of the switch state. To turn the regulator off, press the
switch again, allowing the µC to read the switch status
and pull ONA low. When the switch is released, ONB is
pulled high.
Step-Up DC-DC Converters with Linear Regulator
1 NiCd/NiMH
2 NiCd/NiMH
2 NiCd/NiMH
3 NiCd/NiMH or 1 Li-Ion
NUMBER OF CELLS
CONTROL
INPUTS
I/O
GND
C
LX
Adding a Manual Power Reset
______________________________________________________________________________________
MAX1705
MAX1706
LDO
Implementing Soft-Start
POUT
1- to 3-Cell, High-Current, Low-Noise,
INPUT VOLTAGE
RF
(V)
1.2
2.4
2.4
3.6
PA
STEP-UP OUTPUT VOLTAGE:
TRANSISTOR COUNT: 1649
SUBSTRATE CONNECTED TO GND
Figure 10. Momentary Pushbutton On/Off Switch
___________________Chip Information
ON/OFF
(PA POWER SUPPLY)
(V)
3.3
3.3
5.0
5.0
270k
0.1 F
ONB
ONA
MAX1705
MAX1706
TOTAL OUTPUT CURRENT
270k
MAX1705
OUT
300
730
500
850
(mA)
MAX1706
V
I/O
I/O
DD
200
450
350
550
C
17