MAX5061 Maxim Integrated Products, MAX5061 Datasheet - Page 17

• Manufacturer Part Number: MAX5061
• Description: (MAX5060 / MAX5061) Average-Current-Mode DC-DC Controllers
• Manufacturer: Maxim Integrated Products

The internal oscillator generates a clock with the fre-
quency proportional to the inverse of R
frequency is adjustable from 125kHz to 1.5MHz with
better than 8% accuracy using a single resistor con-
nected from RT/SYNC to SGND (MAX5060) and from
RT/SYNC/EN to SGND (MAX5061). The frequency accu-
racy avoids the over-design, size, and cost of passive
filter components like inductors and capacitors. Use the
following equation to calculate the oscillator frequency:
for 120k
for 40k
Figure 5. MAX5060 Control Loop
SENSE+
SENSE-
*R
F
AND R
IN
AMP
DIFF
ARE EXTERNAL.
R
R
T
T
120k :
Average-Current-Mode DC-DC Controllers
500k :
R
R
______________________________________________________________________________________
T
R
T
IN
*
. 6 40
. 6 25
V
REF
VEA
f
f
R
SW
SW
+ V
F
*
Internal Oscillator
CM
10
10
MAX5060
0.6V to 5.5V Output, Parallelable,
10
10
CSN
CA
T
. The oscillator
CSP
CEA
CLP
CPWM
R
CF
The oscillator also generates a 2V
nal for the PWM comparator and a 180° out-of-phase
clock signal for CLKOUT (MAX5060) to drive a second
DC-DC converter out-of-phase.
The MAX5060/MAX5061 can be easily synchronized by
connecting an external clock to RT/SYNC (MAX5060) or
RT/SYNC/EN (MAX5061). If an external clock is pre-
sent, then the internal oscillator is disabled and the
external clock is used to run the MAX5060/MAX5061. If
the external clock is removed, the absence of clock for
32µs is detected and the circuit starts switching from
the internal oscillator. Pulling RT/SYNC on the MAX5060
or RT/SYNC/EN on the MAX5061 to ground for at least
50µs disables the converter.
Use an open-collector transistor to synchronize the
MAX5060/MAX5061 with the external system clock (see
Figures 1 and 2).
C
C
CFF
CF
DRIVE
V
IN
I
L
R
S
P-P
Synchronization
C
OUT
voltage-ramp sig-
V
LOAD
OUT
17