MAX1765EEE-T Maxim Integrated Products, MAX1765EEE-T Datasheet - Page 11

• Manufacturer Part Number: MAX1765EEE-T
• Description: DC/DC Switching Converters 800mA Step-Up w/500mA Linear Reg
• Manufacturer: Maxim Integrated Products

Figure 1. Functional Diagram
Table 1. Selecting the Operating Mode
E xter nal C l ock
500kH z to
1.2M H z
CLK/SEL
800mA, Low-Noise, Step-Up DC-DC Converter
CLK/SEL
0
1
TRACK
GND
ONA
ISET
OUT
ONB
ONL
FBL
REF
FB
2.15V
______________________________________________________________________________________
V
Normal
Operation
Forced PWM
Synchronized
PWM
IC PWR
OUT
- 300mV
MODE
V
OUT
ON
High-efficiency pulse
skipping at light loads,
PWM at medium and
heavy loads
Low noise, fixed
frequency at all loads
Low noise, fixed
frequency at all loads
REFERENCE
1.250V
FEATURES
RDY
with 500mA Linear Regulator
SHUTDOWN
THERMAL
SENSOR
LOGIC
TRACK
ONL
REF
EN
EN
less power. SKIP mode allows higher efficiency than
PWM under light-load conditions.
At light loads, the MAX1765 operates by turning on the
DC-DC converter’s N-channel field-effect transistor
(FET) when V
edge of the oscillator. The N-channel FET will remain
on, ramping up the inductor current past the minimum
inductor current, until the internal error amplifier and
current mode circuitry determine that the needs of the
system have been met or the device hits the ISET cur-
rent limit. The N-channel is then turned off and the P-
channel is turned on until current decays to the
P-channel turn-off current level. The N-channel will
remain off until V
edge of the oscillator occurs.
OSCILLATOR
OSCILLATOR
1MHz
STARTUP
ERROR
AMP
SKIP/PWM
Q
FB
Light-Load Operation in Normal Mode
FB
< V
MOSFET DRIVER
is again less than V
WITH CURRENT
D
EN
OSC
IFB
MODE
IREF
REF
CONTROLLER
LIMITING
PWM
ISET
, synchronized with the rising
MAX1765
ICS
Q
Q
N
P
P
REF
, and a rising
POUT
PGND
OUTL
INL
LX
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