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MAX5094AASA+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22
MAX5094A/B/C/D/MAX5095A/B/C
High-Performance, Single-Ended, Current-Mode
PWM Controllers
10 ______________________________________________________________________________________
Pin Descriptions (continued)
PIN
MAX5095A/
MAX5095B
MAX5095C
NAME FUNCTION
1 1 COMP
Current Limit/PWM Comparator Input. COMP is level-shifted and connected to the
inverting input of the PWM comparator. Pull up COMP to REF through a resistor and
connect an optocoupler from COMP to GND for proper operation.
2 — SYNC
Bidirectional Synchronization Input. When synchronizing with other
MAX5095A/MAX5095Bs, the higher frequency part synchronizes all other devices.
—2
ADV_CLK
Advance Clock Output. ADV_CLK is an 85ns clock output pulse preceding the rising
edge of OUT (see Figure 4). Use the pulse to drive the secondary-side synchronous
rectifiers through a pulse transformer or an optocoupler (see Figure 8).
33CS
PWM Comparator/Overcurrent Protection Comparator Input. The current-sense signal is
compared to the level shifted voltage at COMP.
44R
T
/C
T
Timing Resistor/Capacitor Connection. A resistor R
T
from R
T
/C
T
to REF and capacitor C
T
from R
T
/C
T
to GND set the oscillator frequency.
5 5 GND
Power-Supply Ground. Place the V
CC
and REF bypass capacitors close to the IC to
minimize ground loops.
6 6 OUT MOSFET Driver Output. OUT connects to the gate of the external n-channel MOSFET.
77V
CC
Power-Supply Input. Bypass V
CC
to GND with a 0.1µF ceramic capacitor or a parallel
combination of a 0.1µF and a higher value ceramic capacitor.
8 8 REF
5V Reference Output. Bypass REF to GND with a 0.1µF ceramic capacitor or a parallel
combination of a 0.1µF and a higher value ceramic capacitor no larger than 4.7µF.
MAX5095_
Detailed Description
The MAX5094_/MAX5095_ current-mode PWM con-
trollers are designed for use as the control and regulation
core of flyback or forward topology switching power sup-
plies. These devices incorporate an integrated low-side
driver, adjustable oscillator, error amplifier (MAX5094_
only), current-sense amplifier, 5V reference, and external
synchronization capability (MAX5095A/MAX5095B only).
An internal +26.5V current-limited V
CC
clamp prevents
overvoltage during startup.
Eight different versions of the MAX5094/MAX5095 are
available as shown in the Selector Guide. The
MAX5094A/MAX5094B are the standard versions with a
feedback input (FB) and internal error amplifier. The
MAX5095A/MAX5095B include bidirectional synchroniza-
tion (SYNC). This enables multiple MAX5095A/
MAX5095Bs to be connected and synchronized to the
device with the highest frequency. The MAX5095C
includes an ADV_CLK output, which precedes the
MAX5095C’s drive output (OUT) by 110ns. Figures 1, 2,
and 3 show the internal functional diagrams of the
MAX5094_, MAX5095A/MAX5095B, and MAX5095C,
respectively. The MAX5094A/MAX5094C/MAX5095A are
capable of 100% maximum duty cycle. The MAX5094B/
MAX5094D/MAX5095B/MAX5095C limit the maximum
duty cycle to 50%.
MAX5094A/B/C/D/MAX5095A/B/C
High-Performance, Single-Ended, Current-Mode
PWM Controllers
______________________________________________________________________________________ 11
UVLO
REFERENCE
2.5V
PREREGULATOR
5V
VOLTAGE-
DIVIDER
THERMAL
SHUTDOWN
EN-REF
BG
SNS
V
DD
5V REGULATOR
VOLTAGE-
DIVIDER
8
7
26.5V
V
CC
REF
2.5V
VP
REG_OK
DELAY
S
R
Q
OSC Q
4
R
T
/C
T
6
OUT
ILIM
CPWM
1V (MAX5094A/B)
0.3V (MAX5094C/D)
EN-DRV-BAR
R
2R
VEA
3
5
2
1
CS
GND
FB
COMP
CLK
MAX5094_
VP
2.5V
8.4V/7.6V
100% MAX DUTY CYCLE (MAX5094A/MAX5094C)
50% MAX DUTY CYCLE (MAX5094B/MAX5094D)
Figure 1. MAX5094_ Functional Diagram
MAX5094A/B/C/D/MAX5095A/B/C
Current-Mode Control Loop
The advantages of current-mode control over voltage-
mode control are twofold. First, there is the feed-forward
characteristic brought on by the controller’s ability to
adjust for variations in the input voltage on a cycle-by-
cycle basis. Secondly, the stability requirements of the
current-mode controller are reduced to that of a single-
pole system unlike the double pole in the voltage-mode
control scheme.
The MAX5094/MAX5095 use a current-mode control loop
where the output of the error amplifier is compared to the
current-sense voltage (V
CS
). When the current-sense sig-
nal is lower than the inverting input of the CPWM com-
parator, the output of the comparator is low and the
switch is turned on at each clock pulse. When the cur-
rent-sense signal is higher than the inverting input of the
CPWM comparator, the output is high and the switch is
turned off.
High-Performance, Single-Ended, Current-Mode
PWM Controllers
12 ______________________________________________________________________________________
UVLO
REFERENCE
2.5V
PREREGULATOR
5V
VOLTAGE-
DIVIDER
THERMAL
SHUTDOWN
EN-REF
BG
SNS
V
DD
5V REGULATOR
VOLTAGE-
DIVIDER
8
7
26.5V
V
CC
REF
2.5V
VP
REG_OK
DELAY
S
R
Q
OSC Q
4
R
T
/C
T
6
OUT
ILIM
CPWM
0.3V
EN-DRV-BAR
R
2R
3
5
1
2
CS
GND
COMP
SYNC
CLK
MAX5095A
MAX5095B
VP
2.5V
BIDIRECTIONAL
SYNC
100% MAX DUTY CYCLE (MAX5095A)
50% MAX DUTY CYCLE (MAX5095B)
8.4V/7.6V
Figure 2. MAX5095A/B Functional Diagram
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22

MAX5094AASA+T

Mfr. #:
Buy MAX5094AASA+T
Manufacturer:
Maxim Integrated
Description:
Switching Controllers Single-Ended
Lifecycle:
New from this manufacturer.
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